[v5,10/10] drm/fb_helper: Support framebuffers in I/O memory

Commit Message

Thomas Zimmermann Oct. 20, 2020, 12:20 p.m. UTC

At least sparc64 requires I/O-specific access to framebuffers. This
patch updates the fbdev console accordingly.

For drivers with direct access to the framebuffer memory, the callback
functions in struct fb_ops test for the type of memory and call the rsp
fb_sys_ of fb_cfb_ functions. Read and write operations are implemented
internally by DRM's fbdev helper.

For drivers that employ a shadow buffer, fbdev's blit function retrieves
the framebuffer address as struct dma_buf_map, and uses dma_buf_map
interfaces to access the buffer.

The bochs driver on sparc64 uses a workaround to flag the framebuffer as
I/O memory and avoid a HW exception. With the introduction of struct
dma_buf_map, this is not required any longer. The patch removes the rsp
code from both, bochs and fbdev.

v5:
	* implement fb_read/fb_write internally (Daniel, Sam)
v4:
	* move dma_buf_map changes into separate patch (Daniel)
	* TODO list: comment on fbdev updates (Daniel)

Signed-off-by: Thomas Zimmermann <[e-mail]>
Tested-by: Sam Ravnborg <[e-mail]>
---
 Documentation/gpu/todo.rst        |  19 ++-
 drivers/gpu/drm/bochs/bochs_kms.c |   1 -
 drivers/gpu/drm/drm_fb_helper.c   | 227 ++++++++++++++++++++++++++++--
 include/drm/drm_mode_config.h     |  12 --
 4 files changed, 230 insertions(+), 29 deletions(-)

Comments

Daniel Vetter Oct. 22, 2020, 8:05 a.m. UTC | #1

On Tue, Oct 20, 2020 at 02:20:46PM +0200, Thomas Zimmermann wrote:
> At least sparc64 requires I/O-specific access to framebuffers. This
> patch updates the fbdev console accordingly.
> 
> For drivers with direct access to the framebuffer memory, the callback
> functions in struct fb_ops test for the type of memory and call the rsp
> fb_sys_ of fb_cfb_ functions. Read and write operations are implemented
> internally by DRM's fbdev helper.
> 
> For drivers that employ a shadow buffer, fbdev's blit function retrieves
> the framebuffer address as struct dma_buf_map, and uses dma_buf_map
> interfaces to access the buffer.
> 
> The bochs driver on sparc64 uses a workaround to flag the framebuffer as
> I/O memory and avoid a HW exception. With the introduction of struct
> dma_buf_map, this is not required any longer. The patch removes the rsp
> code from both, bochs and fbdev.
> 
> v5:
> 	* implement fb_read/fb_write internally (Daniel, Sam)
> v4:
> 	* move dma_buf_map changes into separate patch (Daniel)
> 	* TODO list: comment on fbdev updates (Daniel)
> 
> Signed-off-by: Thomas Zimmermann <[e-mail]>
> Tested-by: Sam Ravnborg <[e-mail]>
> ---
>  Documentation/gpu/todo.rst        |  19 ++-
>  drivers/gpu/drm/bochs/bochs_kms.c |   1 -
>  drivers/gpu/drm/drm_fb_helper.c   | 227 ++++++++++++++++++++++++++++--
>  include/drm/drm_mode_config.h     |  12 --
>  4 files changed, 230 insertions(+), 29 deletions(-)
> 
> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
> index 7e6fc3c04add..638b7f704339 100644
> --- a/Documentation/gpu/todo.rst
> +++ b/Documentation/gpu/todo.rst
> @@ -197,13 +197,28 @@ Convert drivers to use drm_fbdev_generic_setup()
>  ------------------------------------------------
>  
>  Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
> -atomic modesetting and GEM vmap support. Current generic fbdev emulation
> -expects the framebuffer in system memory (or system-like memory).
> +atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
> +expected the framebuffer in system memory or system-like memory. By employing
> +struct dma_buf_map, drivers with frambuffers in I/O memory can be supported
> +as well.
>  
>  Contact: Maintainer of the driver you plan to convert
>  
>  Level: Intermediate
>  
> +Reimplement functions in drm_fbdev_fb_ops without fbdev
> +-------------------------------------------------------
> +
> +A number of callback functions in drm_fbdev_fb_ops could benefit from
> +being rewritten without dependencies on the fbdev module. Some of the
> +helpers could further benefit from using struct dma_buf_map instead of
> +raw pointers.
> +
> +Contact: Thomas Zimmermann <[e-mail]>, Daniel Vetter
> +
> +Level: Advanced
> +
> +
>  drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
>  -----------------------------------------------------------------
>  
> diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c
> index 13d0d04c4457..853081d186d5 100644
> --- a/drivers/gpu/drm/bochs/bochs_kms.c
> +++ b/drivers/gpu/drm/bochs/bochs_kms.c
> @@ -151,7 +151,6 @@ int bochs_kms_init(struct bochs_device *bochs)
>  	bochs->dev->mode_config.preferred_depth = 24;
>  	bochs->dev->mode_config.prefer_shadow = 0;
>  	bochs->dev->mode_config.prefer_shadow_fbdev = 1;
> -	bochs->dev->mode_config.fbdev_use_iomem = true;
>  	bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;
>  
>  	bochs->dev->mode_config.funcs = &bochs_mode_funcs;
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 6212cd7cde1d..1d3180841778 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -372,24 +372,22 @@ static void drm_fb_helper_resume_worker(struct work_struct *work)
>  }
>  
>  static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
> -					  struct drm_clip_rect *clip)
> +					  struct drm_clip_rect *clip,
> +					  struct dma_buf_map *dst)
>  {
>  	struct drm_framebuffer *fb = fb_helper->fb;
>  	unsigned int cpp = fb->format->cpp[0];
>  	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
>  	void *src = fb_helper->fbdev->screen_buffer + offset;
> -	void *dst = fb_helper->buffer->map.vaddr + offset;
>  	size_t len = (clip->x2 - clip->x1) * cpp;
>  	unsigned int y;
>  
> -	for (y = clip->y1; y < clip->y2; y++) {
> -		if (!fb_helper->dev->mode_config.fbdev_use_iomem)
> -			memcpy(dst, src, len);
> -		else
> -			memcpy_toio((void __iomem *)dst, src, len);
> +	dma_buf_map_incr(dst, offset); /* go to first pixel within clip rect */
>  
> +	for (y = clip->y1; y < clip->y2; y++) {
> +		dma_buf_map_memcpy_to(dst, src, len);
> +		dma_buf_map_incr(dst, fb->pitches[0]);
>  		src += fb->pitches[0];
> -		dst += fb->pitches[0];
>  	}
>  }
>  
> @@ -417,8 +415,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
>  			ret = drm_client_buffer_vmap(helper->buffer, &map);
>  			if (ret)
>  				return;
> -			drm_fb_helper_dirty_blit_real(helper, &clip_copy);
> +			drm_fb_helper_dirty_blit_real(helper, &clip_copy, &map);
>  		}
> +
>  		if (helper->fb->funcs->dirty)
>  			helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,
>  						 &clip_copy, 1);
> @@ -2027,6 +2026,206 @@ static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
>  		return -ENODEV;
>  }
>  
> +static bool drm_fbdev_use_iomem(struct fb_info *info)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +	struct drm_client_buffer *buffer = fb_helper->buffer;
> +
> +	return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;
> +}
> +
> +static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_t count, 
> +				   loff_t pos)
> +{
> +	const char __iomem *src = info->screen_base + pos;

Maybe a bit much a bikeshed, but I'd write this in terms of drm objects,
like the dirty_blit function, using the dma_buf_map (instead of the
fb_info parameter). And then instead of
screen_base and screen_buffer suffixes give them _mem and _iomem suffixes.

Same for write below. Or I'm not quite understanding why we do it like
this here - I don't think this code will be used outside of the generic
fbdev code, so we can always assume that drm_fb_helper->buffer is set up.

The other thing I think we need is some minimal testcases to make sure.
The fbtest tool used way back seems to have disappeared, I couldn't find
a copy of the source anywhere anymore.

With all that: Acked-by: Daniel Vetter <[e-mail]>

Cheers, Daniel

> +	size_t alloc_size = min(count, PAGE_SIZE);
> +	ssize_t ret = 0;
> +	char *tmp;
> +
> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
> +	if (!tmp)
> +		return -ENOMEM;
> +
> +	while (count) {
> +		size_t c = min(count, alloc_size);
> +
> +		memcpy_fromio(tmp, src, c);
> +		if (copy_to_user(buf, tmp, c)) {
> +			ret = -EFAULT;
> +			break;
> +		}
> +
> +		src += c;
> +		buf += c;
> +		ret += c;
> +		count -= c;
> +	}
> +
> +	kfree(tmp);
> +
> +	return ret;
> +}
> +
> +static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, size_t count,
> +				     loff_t pos)
> +{
> +	const char *src = info->screen_buffer + pos;
> +
> +	if (copy_to_user(buf, src, count))
> +		return -EFAULT;
> +
> +	return count;
> +}
> +
> +static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,
> +				 size_t count, loff_t *ppos)
> +{
> +	loff_t pos = *ppos;
> +	size_t total_size;
> +	ssize_t ret;
> +
> +	if (info->state != FBINFO_STATE_RUNNING)
> +		return -EPERM;
> +
> +	if (info->screen_size)
> +		total_size = info->screen_size;
> +	else
> +		total_size = info->fix.smem_len;
> +
> +	if (pos >= total_size)
> +		return 0;
> +	if (count >= total_size)
> +		count = total_size;
> +	if (total_size - count < pos)
> +		count = total_size - pos;
> +
> +	if (drm_fbdev_use_iomem(info))
> +		ret = fb_read_screen_base(info, buf, count, pos);
> +	else
> +		ret = fb_read_screen_buffer(info, buf, count, pos);
> +
> +	if (ret > 0)
> +		*ppos = ret;
> +
> +	return ret;
> +}
> +
> +static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf, size_t count,
> +				    loff_t pos)
> +{
> +	char __iomem *dst = info->screen_base + pos;
> +	size_t alloc_size = min(count, PAGE_SIZE);
> +	ssize_t ret = 0;
> +	u8 *tmp;
> +
> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
> +	if (!tmp)
> +		return -ENOMEM;
> +
> +	while (count) {
> +		size_t c = min(count, alloc_size);
> +
> +		if (copy_from_user(tmp, buf, c)) {
> +			ret = -EFAULT;
> +			break;
> +		}
> +		memcpy_toio(dst, tmp, c);
> +
> +		dst += c;
> +		buf += c;
> +		ret += c;
> +		count -= c;
> +	}
> +
> +	kfree(tmp);
> +
> +	return ret;
> +}
> +
> +static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user *buf, size_t count,
> +				      loff_t pos)
> +{
> +	char *dst = info->screen_buffer + pos;
> +
> +	if (copy_from_user(dst, buf, count))
> +		return -EFAULT;
> +
> +	return count;
> +}
> +
> +static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
> +				  size_t count, loff_t *ppos)
> +{
> +	loff_t pos = *ppos;
> +	size_t total_size;
> +	ssize_t ret;
> +	int err;
> +
> +	if (info->state != FBINFO_STATE_RUNNING)
> +		return -EPERM;
> +
> +	if (info->screen_size)
> +		total_size = info->screen_size;
> +	else
> +		total_size = info->fix.smem_len;
> +
> +	if (pos > total_size)
> +		return -EFBIG;
> +	if (count > total_size) {
> +		err = -EFBIG;
> +		count = total_size;
> +	}
> +	if (total_size - count < pos) {
> +		if (!err)
> +			err = -ENOSPC;
> +		count = total_size - pos;
> +	}
> +
> +	/*
> +	 * Copy to framebuffer even if we already logged an error. Emulates
> +	 * the behavior of the original fbdev implementation.
> +	 */
> +	if (drm_fbdev_use_iomem(info))
> +		ret = fb_write_screen_base(info, buf, count, pos);
> +	else
> +		ret = fb_write_screen_buffer(info, buf, count, pos);
> +
> +	if (ret > 0)
> +		*ppos = ret;
> +
> +	if (err)
> +		return err;
> +
> +	return ret;
> +}
> +
> +static void drm_fbdev_fb_fillrect(struct fb_info *info,
> +				  const struct fb_fillrect *rect)
> +{
> +	if (drm_fbdev_use_iomem(info))
> +		drm_fb_helper_cfb_fillrect(info, rect);
> +	else
> +		drm_fb_helper_sys_fillrect(info, rect);
> +}
> +
> +static void drm_fbdev_fb_copyarea(struct fb_info *info,
> +				  const struct fb_copyarea *area)
> +{
> +	if (drm_fbdev_use_iomem(info))
> +		drm_fb_helper_cfb_copyarea(info, area);
> +	else
> +		drm_fb_helper_sys_copyarea(info, area);
> +}
> +
> +static void drm_fbdev_fb_imageblit(struct fb_info *info,
> +				   const struct fb_image *image)
> +{
> +	if (drm_fbdev_use_iomem(info))
> +		drm_fb_helper_cfb_imageblit(info, image);
> +	else
> +		drm_fb_helper_sys_imageblit(info, image);
> +}
> +
>  static const struct fb_ops drm_fbdev_fb_ops = {
>  	.owner		= THIS_MODULE,
>  	DRM_FB_HELPER_DEFAULT_OPS,
> @@ -2034,11 +2233,11 @@ static const struct fb_ops drm_fbdev_fb_ops = {
>  	.fb_release	= drm_fbdev_fb_release,
>  	.fb_destroy	= drm_fbdev_fb_destroy,
>  	.fb_mmap	= drm_fbdev_fb_mmap,
> -	.fb_read	= drm_fb_helper_sys_read,
> -	.fb_write	= drm_fb_helper_sys_write,
> -	.fb_fillrect	= drm_fb_helper_sys_fillrect,
> -	.fb_copyarea	= drm_fb_helper_sys_copyarea,
> -	.fb_imageblit	= drm_fb_helper_sys_imageblit,
> +	.fb_read	= drm_fbdev_fb_read,
> +	.fb_write	= drm_fbdev_fb_write,
> +	.fb_fillrect	= drm_fbdev_fb_fillrect,
> +	.fb_copyarea	= drm_fbdev_fb_copyarea,
> +	.fb_imageblit	= drm_fbdev_fb_imageblit,
>  };
>  
>  static struct fb_deferred_io drm_fbdev_defio = {
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index 5ffbb4ed5b35..ab424ddd7665 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -877,18 +877,6 @@ struct drm_mode_config {
>  	 */
>  	bool prefer_shadow_fbdev;
>  
> -	/**
> -	 * @fbdev_use_iomem:
> -	 *
> -	 * Set to true if framebuffer reside in iomem.
> -	 * When set to true memcpy_toio() is used when copying the framebuffer in
> -	 * drm_fb_helper.drm_fb_helper_dirty_blit_real().
> -	 *
> -	 * FIXME: This should be replaced with a per-mapping is_iomem
> -	 * flag (like ttm does), and then used everywhere in fbdev code.
> -	 */
> -	bool fbdev_use_iomem;
> -
>  	/**
>  	 * @quirk_addfb_prefer_xbgr_30bpp:
>  	 *
> -- 
> 2.28.0
>

Thomas Zimmermann Oct. 22, 2020, 8:37 a.m. UTC | #2

Hi

On 22.10.20 10:05, Daniel Vetter wrote:
> On Tue, Oct 20, 2020 at 02:20:46PM +0200, Thomas Zimmermann wrote:
>> At least sparc64 requires I/O-specific access to framebuffers. This
>> patch updates the fbdev console accordingly.
>>
>> For drivers with direct access to the framebuffer memory, the callback
>> functions in struct fb_ops test for the type of memory and call the rsp
>> fb_sys_ of fb_cfb_ functions. Read and write operations are implemented
>> internally by DRM's fbdev helper.
>>
>> For drivers that employ a shadow buffer, fbdev's blit function retrieves
>> the framebuffer address as struct dma_buf_map, and uses dma_buf_map
>> interfaces to access the buffer.
>>
>> The bochs driver on sparc64 uses a workaround to flag the framebuffer as
>> I/O memory and avoid a HW exception. With the introduction of struct
>> dma_buf_map, this is not required any longer. The patch removes the rsp
>> code from both, bochs and fbdev.
>>
>> v5:
>> 	* implement fb_read/fb_write internally (Daniel, Sam)
>> v4:
>> 	* move dma_buf_map changes into separate patch (Daniel)
>> 	* TODO list: comment on fbdev updates (Daniel)
>>
>> Signed-off-by: Thomas Zimmermann <[e-mail]>
>> Tested-by: Sam Ravnborg <[e-mail]>
>> ---
>>  Documentation/gpu/todo.rst        |  19 ++-
>>  drivers/gpu/drm/bochs/bochs_kms.c |   1 -
>>  drivers/gpu/drm/drm_fb_helper.c   | 227 ++++++++++++++++++++++++++++--
>>  include/drm/drm_mode_config.h     |  12 --
>>  4 files changed, 230 insertions(+), 29 deletions(-)
>>
>> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
>> index 7e6fc3c04add..638b7f704339 100644
>> --- a/Documentation/gpu/todo.rst
>> +++ b/Documentation/gpu/todo.rst
>> @@ -197,13 +197,28 @@ Convert drivers to use drm_fbdev_generic_setup()
>>  ------------------------------------------------
>>  
>>  Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
>> -atomic modesetting and GEM vmap support. Current generic fbdev emulation
>> -expects the framebuffer in system memory (or system-like memory).
>> +atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
>> +expected the framebuffer in system memory or system-like memory. By employing
>> +struct dma_buf_map, drivers with frambuffers in I/O memory can be supported
>> +as well.
>>  
>>  Contact: Maintainer of the driver you plan to convert
>>  
>>  Level: Intermediate
>>  
>> +Reimplement functions in drm_fbdev_fb_ops without fbdev
>> +-------------------------------------------------------
>> +
>> +A number of callback functions in drm_fbdev_fb_ops could benefit from
>> +being rewritten without dependencies on the fbdev module. Some of the
>> +helpers could further benefit from using struct dma_buf_map instead of
>> +raw pointers.
>> +
>> +Contact: Thomas Zimmermann <[e-mail]>, Daniel Vetter
>> +
>> +Level: Advanced
>> +
>> +
>>  drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
>>  -----------------------------------------------------------------
>>  
>> diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c
>> index 13d0d04c4457..853081d186d5 100644
>> --- a/drivers/gpu/drm/bochs/bochs_kms.c
>> +++ b/drivers/gpu/drm/bochs/bochs_kms.c
>> @@ -151,7 +151,6 @@ int bochs_kms_init(struct bochs_device *bochs)
>>  	bochs->dev->mode_config.preferred_depth = 24;
>>  	bochs->dev->mode_config.prefer_shadow = 0;
>>  	bochs->dev->mode_config.prefer_shadow_fbdev = 1;
>> -	bochs->dev->mode_config.fbdev_use_iomem = true;
>>  	bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;
>>  
>>  	bochs->dev->mode_config.funcs = &bochs_mode_funcs;
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 6212cd7cde1d..1d3180841778 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -372,24 +372,22 @@ static void drm_fb_helper_resume_worker(struct work_struct *work)
>>  }
>>  
>>  static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
>> -					  struct drm_clip_rect *clip)
>> +					  struct drm_clip_rect *clip,
>> +					  struct dma_buf_map *dst)
>>  {
>>  	struct drm_framebuffer *fb = fb_helper->fb;
>>  	unsigned int cpp = fb->format->cpp[0];
>>  	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
>>  	void *src = fb_helper->fbdev->screen_buffer + offset;
>> -	void *dst = fb_helper->buffer->map.vaddr + offset;
>>  	size_t len = (clip->x2 - clip->x1) * cpp;
>>  	unsigned int y;
>>  
>> -	for (y = clip->y1; y < clip->y2; y++) {
>> -		if (!fb_helper->dev->mode_config.fbdev_use_iomem)
>> -			memcpy(dst, src, len);
>> -		else
>> -			memcpy_toio((void __iomem *)dst, src, len);
>> +	dma_buf_map_incr(dst, offset); /* go to first pixel within clip rect */
>>  
>> +	for (y = clip->y1; y < clip->y2; y++) {
>> +		dma_buf_map_memcpy_to(dst, src, len);
>> +		dma_buf_map_incr(dst, fb->pitches[0]);
>>  		src += fb->pitches[0];
>> -		dst += fb->pitches[0];
>>  	}
>>  }
>>  
>> @@ -417,8 +415,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
>>  			ret = drm_client_buffer_vmap(helper->buffer, &map);
>>  			if (ret)
>>  				return;
>> -			drm_fb_helper_dirty_blit_real(helper, &clip_copy);
>> +			drm_fb_helper_dirty_blit_real(helper, &clip_copy, &map);
>>  		}
>> +
>>  		if (helper->fb->funcs->dirty)
>>  			helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,
>>  						 &clip_copy, 1);
>> @@ -2027,6 +2026,206 @@ static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
>>  		return -ENODEV;
>>  }
>>  
>> +static bool drm_fbdev_use_iomem(struct fb_info *info)
>> +{
>> +	struct drm_fb_helper *fb_helper = info->par;
>> +	struct drm_client_buffer *buffer = fb_helper->buffer;
>> +
>> +	return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;
>> +}
>> +
>> +static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_t count, 
>> +				   loff_t pos)
>> +{
>> +	const char __iomem *src = info->screen_base + pos;
> 
> Maybe a bit much a bikeshed, but I'd write this in terms of drm objects,
> like the dirty_blit function, using the dma_buf_map (instead of the
> fb_info parameter). And then instead of
> screen_base and screen_buffer suffixes give them _mem and _iomem suffixes.

Screen_buffer can be a shadow buffer. Until the blit worker (see
drm_fb_helper_dirty_work() ) completes, it might be more up to date than
the real buffer that's stored in the client.

The orignal fbdev code supported an fb_sync callback to synchronize with
outstanding screen updates (e.g., HW blit ops), but fb_sync is just
overhead here. Copying from screen_buffer or screen_base always returns
the most up-to-date image.

> 
> Same for write below. Or I'm not quite understanding why we do it like
> this here - I don't think this code will be used outside of the generic
> fbdev code, so we can always assume that drm_fb_helper->buffer is set up.

It's similar as in the read case. If we write to the client's buffer, an
outstanding blit worker could write the now-outdated shadow buffer over
the user's newly written framebuffer data.

Thinking about it, we might want to schedule the blit worker at the end
of each fb_write, so that the data makes it into the HW buffer in time.

> 
> The other thing I think we need is some minimal testcases to make sure.
> The fbtest tool used way back seems to have disappeared, I couldn't find
> a copy of the source anywhere anymore.

As discussed on IRC, I'll add some testcase to the igt test. I'll share
the link here when done.

Best regards
Thomas

> 
> With all that: Acked-by: Daniel Vetter <[e-mail]>
> 
> Cheers, Daniel
> 
>> +	size_t alloc_size = min(count, PAGE_SIZE);
>> +	ssize_t ret = 0;
>> +	char *tmp;
>> +
>> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
>> +	if (!tmp)
>> +		return -ENOMEM;
>> +
>> +	while (count) {
>> +		size_t c = min(count, alloc_size);
>> +
>> +		memcpy_fromio(tmp, src, c);
>> +		if (copy_to_user(buf, tmp, c)) {
>> +			ret = -EFAULT;
>> +			break;
>> +		}
>> +
>> +		src += c;
>> +		buf += c;
>> +		ret += c;
>> +		count -= c;
>> +	}
>> +
>> +	kfree(tmp);
>> +
>> +	return ret;
>> +}
>> +
>> +static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, size_t count,
>> +				     loff_t pos)
>> +{
>> +	const char *src = info->screen_buffer + pos;
>> +
>> +	if (copy_to_user(buf, src, count))
>> +		return -EFAULT;
>> +
>> +	return count;
>> +}
>> +
>> +static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,
>> +				 size_t count, loff_t *ppos)
>> +{
>> +	loff_t pos = *ppos;
>> +	size_t total_size;
>> +	ssize_t ret;
>> +
>> +	if (info->state != FBINFO_STATE_RUNNING)
>> +		return -EPERM;
>> +
>> +	if (info->screen_size)
>> +		total_size = info->screen_size;
>> +	else
>> +		total_size = info->fix.smem_len;
>> +
>> +	if (pos >= total_size)
>> +		return 0;
>> +	if (count >= total_size)
>> +		count = total_size;
>> +	if (total_size - count < pos)
>> +		count = total_size - pos;
>> +
>> +	if (drm_fbdev_use_iomem(info))
>> +		ret = fb_read_screen_base(info, buf, count, pos);
>> +	else
>> +		ret = fb_read_screen_buffer(info, buf, count, pos);
>> +
>> +	if (ret > 0)
>> +		*ppos = ret;
>> +
>> +	return ret;
>> +}
>> +
>> +static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf, size_t count,
>> +				    loff_t pos)
>> +{
>> +	char __iomem *dst = info->screen_base + pos;
>> +	size_t alloc_size = min(count, PAGE_SIZE);
>> +	ssize_t ret = 0;
>> +	u8 *tmp;
>> +
>> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
>> +	if (!tmp)
>> +		return -ENOMEM;
>> +
>> +	while (count) {
>> +		size_t c = min(count, alloc_size);
>> +
>> +		if (copy_from_user(tmp, buf, c)) {
>> +			ret = -EFAULT;
>> +			break;
>> +		}
>> +		memcpy_toio(dst, tmp, c);
>> +
>> +		dst += c;
>> +		buf += c;
>> +		ret += c;
>> +		count -= c;
>> +	}
>> +
>> +	kfree(tmp);
>> +
>> +	return ret;
>> +}
>> +
>> +static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user *buf, size_t count,
>> +				      loff_t pos)
>> +{
>> +	char *dst = info->screen_buffer + pos;
>> +
>> +	if (copy_from_user(dst, buf, count))
>> +		return -EFAULT;
>> +
>> +	return count;
>> +}
>> +
>> +static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
>> +				  size_t count, loff_t *ppos)
>> +{
>> +	loff_t pos = *ppos;
>> +	size_t total_size;
>> +	ssize_t ret;
>> +	int err;
>> +
>> +	if (info->state != FBINFO_STATE_RUNNING)
>> +		return -EPERM;
>> +
>> +	if (info->screen_size)
>> +		total_size = info->screen_size;
>> +	else
>> +		total_size = info->fix.smem_len;
>> +
>> +	if (pos > total_size)
>> +		return -EFBIG;
>> +	if (count > total_size) {
>> +		err = -EFBIG;
>> +		count = total_size;
>> +	}
>> +	if (total_size - count < pos) {
>> +		if (!err)
>> +			err = -ENOSPC;
>> +		count = total_size - pos;
>> +	}
>> +
>> +	/*
>> +	 * Copy to framebuffer even if we already logged an error. Emulates
>> +	 * the behavior of the original fbdev implementation.
>> +	 */
>> +	if (drm_fbdev_use_iomem(info))
>> +		ret = fb_write_screen_base(info, buf, count, pos);
>> +	else
>> +		ret = fb_write_screen_buffer(info, buf, count, pos);
>> +
>> +	if (ret > 0)
>> +		*ppos = ret;
>> +
>> +	if (err)
>> +		return err;
>> +
>> +	return ret;
>> +}
>> +
>> +static void drm_fbdev_fb_fillrect(struct fb_info *info,
>> +				  const struct fb_fillrect *rect)
>> +{
>> +	if (drm_fbdev_use_iomem(info))
>> +		drm_fb_helper_cfb_fillrect(info, rect);
>> +	else
>> +		drm_fb_helper_sys_fillrect(info, rect);
>> +}
>> +
>> +static void drm_fbdev_fb_copyarea(struct fb_info *info,
>> +				  const struct fb_copyarea *area)
>> +{
>> +	if (drm_fbdev_use_iomem(info))
>> +		drm_fb_helper_cfb_copyarea(info, area);
>> +	else
>> +		drm_fb_helper_sys_copyarea(info, area);
>> +}
>> +
>> +static void drm_fbdev_fb_imageblit(struct fb_info *info,
>> +				   const struct fb_image *image)
>> +{
>> +	if (drm_fbdev_use_iomem(info))
>> +		drm_fb_helper_cfb_imageblit(info, image);
>> +	else
>> +		drm_fb_helper_sys_imageblit(info, image);
>> +}
>> +
>>  static const struct fb_ops drm_fbdev_fb_ops = {
>>  	.owner		= THIS_MODULE,
>>  	DRM_FB_HELPER_DEFAULT_OPS,
>> @@ -2034,11 +2233,11 @@ static const struct fb_ops drm_fbdev_fb_ops = {
>>  	.fb_release	= drm_fbdev_fb_release,
>>  	.fb_destroy	= drm_fbdev_fb_destroy,
>>  	.fb_mmap	= drm_fbdev_fb_mmap,
>> -	.fb_read	= drm_fb_helper_sys_read,
>> -	.fb_write	= drm_fb_helper_sys_write,
>> -	.fb_fillrect	= drm_fb_helper_sys_fillrect,
>> -	.fb_copyarea	= drm_fb_helper_sys_copyarea,
>> -	.fb_imageblit	= drm_fb_helper_sys_imageblit,
>> +	.fb_read	= drm_fbdev_fb_read,
>> +	.fb_write	= drm_fbdev_fb_write,
>> +	.fb_fillrect	= drm_fbdev_fb_fillrect,
>> +	.fb_copyarea	= drm_fbdev_fb_copyarea,
>> +	.fb_imageblit	= drm_fbdev_fb_imageblit,
>>  };
>>  
>>  static struct fb_deferred_io drm_fbdev_defio = {
>> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
>> index 5ffbb4ed5b35..ab424ddd7665 100644
>> --- a/include/drm/drm_mode_config.h
>> +++ b/include/drm/drm_mode_config.h
>> @@ -877,18 +877,6 @@ struct drm_mode_config {
>>  	 */
>>  	bool prefer_shadow_fbdev;
>>  
>> -	/**
>> -	 * @fbdev_use_iomem:
>> -	 *
>> -	 * Set to true if framebuffer reside in iomem.
>> -	 * When set to true memcpy_toio() is used when copying the framebuffer in
>> -	 * drm_fb_helper.drm_fb_helper_dirty_blit_real().
>> -	 *
>> -	 * FIXME: This should be replaced with a per-mapping is_iomem
>> -	 * flag (like ttm does), and then used everywhere in fbdev code.
>> -	 */
>> -	bool fbdev_use_iomem;
>> -
>>  	/**
>>  	 * @quirk_addfb_prefer_xbgr_30bpp:
>>  	 *
>> -- 
>> 2.28.0
>>
>

Daniel Vetter Oct. 22, 2020, 8:51 a.m. UTC | #3

On Thu, Oct 22, 2020 at 10:37:56AM +0200, Thomas Zimmermann wrote:
> Hi
> 
> On 22.10.20 10:05, Daniel Vetter wrote:
> > On Tue, Oct 20, 2020 at 02:20:46PM +0200, Thomas Zimmermann wrote:
> >> At least sparc64 requires I/O-specific access to framebuffers. This
> >> patch updates the fbdev console accordingly.
> >>
> >> For drivers with direct access to the framebuffer memory, the callback
> >> functions in struct fb_ops test for the type of memory and call the rsp
> >> fb_sys_ of fb_cfb_ functions. Read and write operations are implemented
> >> internally by DRM's fbdev helper.
> >>
> >> For drivers that employ a shadow buffer, fbdev's blit function retrieves
> >> the framebuffer address as struct dma_buf_map, and uses dma_buf_map
> >> interfaces to access the buffer.
> >>
> >> The bochs driver on sparc64 uses a workaround to flag the framebuffer as
> >> I/O memory and avoid a HW exception. With the introduction of struct
> >> dma_buf_map, this is not required any longer. The patch removes the rsp
> >> code from both, bochs and fbdev.
> >>
> >> v5:
> >> 	* implement fb_read/fb_write internally (Daniel, Sam)
> >> v4:
> >> 	* move dma_buf_map changes into separate patch (Daniel)
> >> 	* TODO list: comment on fbdev updates (Daniel)
> >>
> >> Signed-off-by: Thomas Zimmermann <[e-mail]>
> >> Tested-by: Sam Ravnborg <[e-mail]>
> >> ---
> >>  Documentation/gpu/todo.rst        |  19 ++-
> >>  drivers/gpu/drm/bochs/bochs_kms.c |   1 -
> >>  drivers/gpu/drm/drm_fb_helper.c   | 227 ++++++++++++++++++++++++++++--
> >>  include/drm/drm_mode_config.h     |  12 --
> >>  4 files changed, 230 insertions(+), 29 deletions(-)
> >>
> >> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
> >> index 7e6fc3c04add..638b7f704339 100644
> >> --- a/Documentation/gpu/todo.rst
> >> +++ b/Documentation/gpu/todo.rst
> >> @@ -197,13 +197,28 @@ Convert drivers to use drm_fbdev_generic_setup()
> >>  ------------------------------------------------
> >>  
> >>  Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
> >> -atomic modesetting and GEM vmap support. Current generic fbdev emulation
> >> -expects the framebuffer in system memory (or system-like memory).
> >> +atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
> >> +expected the framebuffer in system memory or system-like memory. By employing
> >> +struct dma_buf_map, drivers with frambuffers in I/O memory can be supported
> >> +as well.
> >>  
> >>  Contact: Maintainer of the driver you plan to convert
> >>  
> >>  Level: Intermediate
> >>  
> >> +Reimplement functions in drm_fbdev_fb_ops without fbdev
> >> +-------------------------------------------------------
> >> +
> >> +A number of callback functions in drm_fbdev_fb_ops could benefit from
> >> +being rewritten without dependencies on the fbdev module. Some of the
> >> +helpers could further benefit from using struct dma_buf_map instead of
> >> +raw pointers.
> >> +
> >> +Contact: Thomas Zimmermann <[e-mail]>, Daniel Vetter
> >> +
> >> +Level: Advanced
> >> +
> >> +
> >>  drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
> >>  -----------------------------------------------------------------
> >>  
> >> diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c
> >> index 13d0d04c4457..853081d186d5 100644
> >> --- a/drivers/gpu/drm/bochs/bochs_kms.c
> >> +++ b/drivers/gpu/drm/bochs/bochs_kms.c
> >> @@ -151,7 +151,6 @@ int bochs_kms_init(struct bochs_device *bochs)
> >>  	bochs->dev->mode_config.preferred_depth = 24;
> >>  	bochs->dev->mode_config.prefer_shadow = 0;
> >>  	bochs->dev->mode_config.prefer_shadow_fbdev = 1;
> >> -	bochs->dev->mode_config.fbdev_use_iomem = true;
> >>  	bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;
> >>  
> >>  	bochs->dev->mode_config.funcs = &bochs_mode_funcs;
> >> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> >> index 6212cd7cde1d..1d3180841778 100644
> >> --- a/drivers/gpu/drm/drm_fb_helper.c
> >> +++ b/drivers/gpu/drm/drm_fb_helper.c
> >> @@ -372,24 +372,22 @@ static void drm_fb_helper_resume_worker(struct work_struct *work)
> >>  }
> >>  
> >>  static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
> >> -					  struct drm_clip_rect *clip)
> >> +					  struct drm_clip_rect *clip,
> >> +					  struct dma_buf_map *dst)
> >>  {
> >>  	struct drm_framebuffer *fb = fb_helper->fb;
> >>  	unsigned int cpp = fb->format->cpp[0];
> >>  	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
> >>  	void *src = fb_helper->fbdev->screen_buffer + offset;
> >> -	void *dst = fb_helper->buffer->map.vaddr + offset;
> >>  	size_t len = (clip->x2 - clip->x1) * cpp;
> >>  	unsigned int y;
> >>  
> >> -	for (y = clip->y1; y < clip->y2; y++) {
> >> -		if (!fb_helper->dev->mode_config.fbdev_use_iomem)
> >> -			memcpy(dst, src, len);
> >> -		else
> >> -			memcpy_toio((void __iomem *)dst, src, len);
> >> +	dma_buf_map_incr(dst, offset); /* go to first pixel within clip rect */
> >>  
> >> +	for (y = clip->y1; y < clip->y2; y++) {
> >> +		dma_buf_map_memcpy_to(dst, src, len);
> >> +		dma_buf_map_incr(dst, fb->pitches[0]);
> >>  		src += fb->pitches[0];
> >> -		dst += fb->pitches[0];
> >>  	}
> >>  }
> >>  
> >> @@ -417,8 +415,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
> >>  			ret = drm_client_buffer_vmap(helper->buffer, &map);
> >>  			if (ret)
> >>  				return;
> >> -			drm_fb_helper_dirty_blit_real(helper, &clip_copy);
> >> +			drm_fb_helper_dirty_blit_real(helper, &clip_copy, &map);
> >>  		}
> >> +
> >>  		if (helper->fb->funcs->dirty)
> >>  			helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,
> >>  						 &clip_copy, 1);
> >> @@ -2027,6 +2026,206 @@ static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
> >>  		return -ENODEV;
> >>  }
> >>  
> >> +static bool drm_fbdev_use_iomem(struct fb_info *info)
> >> +{
> >> +	struct drm_fb_helper *fb_helper = info->par;
> >> +	struct drm_client_buffer *buffer = fb_helper->buffer;
> >> +
> >> +	return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;
> >> +}
> >> +
> >> +static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_t count, 
> >> +				   loff_t pos)
> >> +{
> >> +	const char __iomem *src = info->screen_base + pos;
> > 
> > Maybe a bit much a bikeshed, but I'd write this in terms of drm objects,
> > like the dirty_blit function, using the dma_buf_map (instead of the
> > fb_info parameter). And then instead of
> > screen_base and screen_buffer suffixes give them _mem and _iomem suffixes.
> 
> Screen_buffer can be a shadow buffer. Until the blit worker (see
> drm_fb_helper_dirty_work() ) completes, it might be more up to date than
> the real buffer that's stored in the client.
> 
> The orignal fbdev code supported an fb_sync callback to synchronize with
> outstanding screen updates (e.g., HW blit ops), but fb_sync is just
> overhead here. Copying from screen_buffer or screen_base always returns
> the most up-to-date image.
> 
> > 
> > Same for write below. Or I'm not quite understanding why we do it like
> > this here - I don't think this code will be used outside of the generic
> > fbdev code, so we can always assume that drm_fb_helper->buffer is set up.
> 
> It's similar as in the read case. If we write to the client's buffer, an
> outstanding blit worker could write the now-outdated shadow buffer over
> the user's newly written framebuffer data.
> 
> Thinking about it, we might want to schedule the blit worker at the end
> of each fb_write, so that the data makes it into the HW buffer in time.

Hm ok, makes some sense. I think there's some potential for cleanup if we
add a dma_buf_map drm_fb_helper->uapi_map which points at the right thing
always. That could then also the drm_fbdev_use_iomem() helper and make
this all look really neat.

But maybe a follow up clean up patch, if you're bored. As-is:

Reviewed-by: Daniel Vetter <[e-mail]>

While looking at this I also noticed a potential small issue in an earlier
patch.

> > The other thing I think we need is some minimal testcases to make sure.
> > The fbtest tool used way back seems to have disappeared, I couldn't find
> > a copy of the source anywhere anymore.
> 
> As discussed on IRC, I'll add some testcase to the igt test. I'll share
> the link here when done.
> 
> Best regards
> Thomas
> 
> > 
> > With all that: Acked-by: Daniel Vetter <[e-mail]>
> > 
> > Cheers, Daniel
> > 
> >> +	size_t alloc_size = min(count, PAGE_SIZE);
> >> +	ssize_t ret = 0;
> >> +	char *tmp;
> >> +
> >> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
> >> +	if (!tmp)
> >> +		return -ENOMEM;
> >> +
> >> +	while (count) {
> >> +		size_t c = min(count, alloc_size);
> >> +
> >> +		memcpy_fromio(tmp, src, c);
> >> +		if (copy_to_user(buf, tmp, c)) {
> >> +			ret = -EFAULT;
> >> +			break;
> >> +		}
> >> +
> >> +		src += c;
> >> +		buf += c;
> >> +		ret += c;
> >> +		count -= c;
> >> +	}
> >> +
> >> +	kfree(tmp);
> >> +
> >> +	return ret;
> >> +}
> >> +
> >> +static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, size_t count,
> >> +				     loff_t pos)
> >> +{
> >> +	const char *src = info->screen_buffer + pos;
> >> +
> >> +	if (copy_to_user(buf, src, count))
> >> +		return -EFAULT;
> >> +
> >> +	return count;
> >> +}
> >> +
> >> +static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,
> >> +				 size_t count, loff_t *ppos)
> >> +{
> >> +	loff_t pos = *ppos;
> >> +	size_t total_size;
> >> +	ssize_t ret;
> >> +
> >> +	if (info->state != FBINFO_STATE_RUNNING)
> >> +		return -EPERM;
> >> +
> >> +	if (info->screen_size)
> >> +		total_size = info->screen_size;
> >> +	else
> >> +		total_size = info->fix.smem_len;
> >> +
> >> +	if (pos >= total_size)
> >> +		return 0;
> >> +	if (count >= total_size)
> >> +		count = total_size;
> >> +	if (total_size - count < pos)
> >> +		count = total_size - pos;
> >> +
> >> +	if (drm_fbdev_use_iomem(info))
> >> +		ret = fb_read_screen_base(info, buf, count, pos);
> >> +	else
> >> +		ret = fb_read_screen_buffer(info, buf, count, pos);
> >> +
> >> +	if (ret > 0)
> >> +		*ppos = ret;
> >> +
> >> +	return ret;
> >> +}
> >> +
> >> +static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf, size_t count,
> >> +				    loff_t pos)
> >> +{
> >> +	char __iomem *dst = info->screen_base + pos;
> >> +	size_t alloc_size = min(count, PAGE_SIZE);
> >> +	ssize_t ret = 0;
> >> +	u8 *tmp;
> >> +
> >> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
> >> +	if (!tmp)
> >> +		return -ENOMEM;
> >> +
> >> +	while (count) {
> >> +		size_t c = min(count, alloc_size);
> >> +
> >> +		if (copy_from_user(tmp, buf, c)) {
> >> +			ret = -EFAULT;
> >> +			break;
> >> +		}
> >> +		memcpy_toio(dst, tmp, c);
> >> +
> >> +		dst += c;
> >> +		buf += c;
> >> +		ret += c;
> >> +		count -= c;
> >> +	}
> >> +
> >> +	kfree(tmp);
> >> +
> >> +	return ret;
> >> +}
> >> +
> >> +static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user *buf, size_t count,
> >> +				      loff_t pos)
> >> +{
> >> +	char *dst = info->screen_buffer + pos;
> >> +
> >> +	if (copy_from_user(dst, buf, count))
> >> +		return -EFAULT;
> >> +
> >> +	return count;
> >> +}
> >> +
> >> +static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
> >> +				  size_t count, loff_t *ppos)
> >> +{
> >> +	loff_t pos = *ppos;
> >> +	size_t total_size;
> >> +	ssize_t ret;
> >> +	int err;
> >> +
> >> +	if (info->state != FBINFO_STATE_RUNNING)
> >> +		return -EPERM;
> >> +
> >> +	if (info->screen_size)
> >> +		total_size = info->screen_size;
> >> +	else
> >> +		total_size = info->fix.smem_len;
> >> +
> >> +	if (pos > total_size)
> >> +		return -EFBIG;
> >> +	if (count > total_size) {
> >> +		err = -EFBIG;
> >> +		count = total_size;
> >> +	}
> >> +	if (total_size - count < pos) {
> >> +		if (!err)
> >> +			err = -ENOSPC;
> >> +		count = total_size - pos;
> >> +	}
> >> +
> >> +	/*
> >> +	 * Copy to framebuffer even if we already logged an error. Emulates
> >> +	 * the behavior of the original fbdev implementation.
> >> +	 */
> >> +	if (drm_fbdev_use_iomem(info))
> >> +		ret = fb_write_screen_base(info, buf, count, pos);
> >> +	else
> >> +		ret = fb_write_screen_buffer(info, buf, count, pos);
> >> +
> >> +	if (ret > 0)
> >> +		*ppos = ret;
> >> +
> >> +	if (err)
> >> +		return err;
> >> +
> >> +	return ret;
> >> +}
> >> +
> >> +static void drm_fbdev_fb_fillrect(struct fb_info *info,
> >> +				  const struct fb_fillrect *rect)
> >> +{
> >> +	if (drm_fbdev_use_iomem(info))
> >> +		drm_fb_helper_cfb_fillrect(info, rect);
> >> +	else
> >> +		drm_fb_helper_sys_fillrect(info, rect);
> >> +}
> >> +
> >> +static void drm_fbdev_fb_copyarea(struct fb_info *info,
> >> +				  const struct fb_copyarea *area)
> >> +{
> >> +	if (drm_fbdev_use_iomem(info))
> >> +		drm_fb_helper_cfb_copyarea(info, area);
> >> +	else
> >> +		drm_fb_helper_sys_copyarea(info, area);
> >> +}
> >> +
> >> +static void drm_fbdev_fb_imageblit(struct fb_info *info,
> >> +				   const struct fb_image *image)
> >> +{
> >> +	if (drm_fbdev_use_iomem(info))
> >> +		drm_fb_helper_cfb_imageblit(info, image);
> >> +	else
> >> +		drm_fb_helper_sys_imageblit(info, image);
> >> +}
> >> +
> >>  static const struct fb_ops drm_fbdev_fb_ops = {
> >>  	.owner		= THIS_MODULE,
> >>  	DRM_FB_HELPER_DEFAULT_OPS,
> >> @@ -2034,11 +2233,11 @@ static const struct fb_ops drm_fbdev_fb_ops = {
> >>  	.fb_release	= drm_fbdev_fb_release,
> >>  	.fb_destroy	= drm_fbdev_fb_destroy,
> >>  	.fb_mmap	= drm_fbdev_fb_mmap,
> >> -	.fb_read	= drm_fb_helper_sys_read,
> >> -	.fb_write	= drm_fb_helper_sys_write,
> >> -	.fb_fillrect	= drm_fb_helper_sys_fillrect,
> >> -	.fb_copyarea	= drm_fb_helper_sys_copyarea,
> >> -	.fb_imageblit	= drm_fb_helper_sys_imageblit,
> >> +	.fb_read	= drm_fbdev_fb_read,
> >> +	.fb_write	= drm_fbdev_fb_write,
> >> +	.fb_fillrect	= drm_fbdev_fb_fillrect,
> >> +	.fb_copyarea	= drm_fbdev_fb_copyarea,
> >> +	.fb_imageblit	= drm_fbdev_fb_imageblit,
> >>  };
> >>  
> >>  static struct fb_deferred_io drm_fbdev_defio = {
> >> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> >> index 5ffbb4ed5b35..ab424ddd7665 100644
> >> --- a/include/drm/drm_mode_config.h
> >> +++ b/include/drm/drm_mode_config.h
> >> @@ -877,18 +877,6 @@ struct drm_mode_config {
> >>  	 */
> >>  	bool prefer_shadow_fbdev;
> >>  
> >> -	/**
> >> -	 * @fbdev_use_iomem:
> >> -	 *
> >> -	 * Set to true if framebuffer reside in iomem.
> >> -	 * When set to true memcpy_toio() is used when copying the framebuffer in
> >> -	 * drm_fb_helper.drm_fb_helper_dirty_blit_real().
> >> -	 *
> >> -	 * FIXME: This should be replaced with a per-mapping is_iomem
> >> -	 * flag (like ttm does), and then used everywhere in fbdev code.
> >> -	 */
> >> -	bool fbdev_use_iomem;
> >> -
> >>  	/**
> >>  	 * @quirk_addfb_prefer_xbgr_30bpp:
> >>  	 *
> >> -- 
> >> 2.28.0
> >>
> > 
> 
> -- 
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer

Sam Ravnborg Oct. 24, 2020, 8:38 p.m. UTC | #4

Hi Thomas.

On Tue, Oct 20, 2020 at 02:20:46PM +0200, Thomas Zimmermann wrote:
> At least sparc64 requires I/O-specific access to framebuffers. This
> patch updates the fbdev console accordingly.
> 
> For drivers with direct access to the framebuffer memory, the callback
> functions in struct fb_ops test for the type of memory and call the rsp
> fb_sys_ of fb_cfb_ functions. Read and write operations are implemented
> internally by DRM's fbdev helper.
> 
> For drivers that employ a shadow buffer, fbdev's blit function retrieves
> the framebuffer address as struct dma_buf_map, and uses dma_buf_map
> interfaces to access the buffer.
> 
> The bochs driver on sparc64 uses a workaround to flag the framebuffer as
> I/O memory and avoid a HW exception. With the introduction of struct
> dma_buf_map, this is not required any longer. The patch removes the rsp
> code from both, bochs and fbdev.
> 
> v5:
> 	* implement fb_read/fb_write internally (Daniel, Sam)
> v4:
> 	* move dma_buf_map changes into separate patch (Daniel)
> 	* TODO list: comment on fbdev updates (Daniel)
> 
> Signed-off-by: Thomas Zimmermann <[e-mail]>
> Tested-by: Sam Ravnborg <[e-mail]>
Reviewed-by: Sam Ravnborg <[e-mail]>

But see a few comments below on naming for you to consider.

	Sam

> ---
>  Documentation/gpu/todo.rst        |  19 ++-
>  drivers/gpu/drm/bochs/bochs_kms.c |   1 -
>  drivers/gpu/drm/drm_fb_helper.c   | 227 ++++++++++++++++++++++++++++--
>  include/drm/drm_mode_config.h     |  12 --
>  4 files changed, 230 insertions(+), 29 deletions(-)
> 
> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
> index 7e6fc3c04add..638b7f704339 100644
> --- a/Documentation/gpu/todo.rst
> +++ b/Documentation/gpu/todo.rst
> @@ -197,13 +197,28 @@ Convert drivers to use drm_fbdev_generic_setup()
>  ------------------------------------------------
>  
>  Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
> -atomic modesetting and GEM vmap support. Current generic fbdev emulation
> -expects the framebuffer in system memory (or system-like memory).
> +atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
> +expected the framebuffer in system memory or system-like memory. By employing
> +struct dma_buf_map, drivers with frambuffers in I/O memory can be supported
> +as well.
>  
>  Contact: Maintainer of the driver you plan to convert
>  
>  Level: Intermediate
>  
> +Reimplement functions in drm_fbdev_fb_ops without fbdev
> +-------------------------------------------------------
> +
> +A number of callback functions in drm_fbdev_fb_ops could benefit from
> +being rewritten without dependencies on the fbdev module. Some of the
> +helpers could further benefit from using struct dma_buf_map instead of
> +raw pointers.
> +
> +Contact: Thomas Zimmermann <[e-mail]>, Daniel Vetter
> +
> +Level: Advanced
> +
> +
>  drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
>  -----------------------------------------------------------------
>  
> diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c
> index 13d0d04c4457..853081d186d5 100644
> --- a/drivers/gpu/drm/bochs/bochs_kms.c
> +++ b/drivers/gpu/drm/bochs/bochs_kms.c
> @@ -151,7 +151,6 @@ int bochs_kms_init(struct bochs_device *bochs)
>  	bochs->dev->mode_config.preferred_depth = 24;
>  	bochs->dev->mode_config.prefer_shadow = 0;
>  	bochs->dev->mode_config.prefer_shadow_fbdev = 1;
> -	bochs->dev->mode_config.fbdev_use_iomem = true;
>  	bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;
>  
>  	bochs->dev->mode_config.funcs = &bochs_mode_funcs;
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 6212cd7cde1d..1d3180841778 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -372,24 +372,22 @@ static void drm_fb_helper_resume_worker(struct work_struct *work)
>  }
>  
>  static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
> -					  struct drm_clip_rect *clip)
> +					  struct drm_clip_rect *clip,
> +					  struct dma_buf_map *dst)
>  {
>  	struct drm_framebuffer *fb = fb_helper->fb;
>  	unsigned int cpp = fb->format->cpp[0];
>  	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
>  	void *src = fb_helper->fbdev->screen_buffer + offset;
> -	void *dst = fb_helper->buffer->map.vaddr + offset;
>  	size_t len = (clip->x2 - clip->x1) * cpp;
>  	unsigned int y;
>  
> -	for (y = clip->y1; y < clip->y2; y++) {
> -		if (!fb_helper->dev->mode_config.fbdev_use_iomem)
> -			memcpy(dst, src, len);
> -		else
> -			memcpy_toio((void __iomem *)dst, src, len);
> +	dma_buf_map_incr(dst, offset); /* go to first pixel within clip rect */
>  
> +	for (y = clip->y1; y < clip->y2; y++) {
> +		dma_buf_map_memcpy_to(dst, src, len);
> +		dma_buf_map_incr(dst, fb->pitches[0]);
>  		src += fb->pitches[0];
> -		dst += fb->pitches[0];
>  	}
>  }
>  
> @@ -417,8 +415,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
>  			ret = drm_client_buffer_vmap(helper->buffer, &map);
>  			if (ret)
>  				return;
> -			drm_fb_helper_dirty_blit_real(helper, &clip_copy);
> +			drm_fb_helper_dirty_blit_real(helper, &clip_copy, &map);
>  		}
> +
>  		if (helper->fb->funcs->dirty)
>  			helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,
>  						 &clip_copy, 1);
> @@ -2027,6 +2026,206 @@ static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
>  		return -ENODEV;
>  }
>  
> +static bool drm_fbdev_use_iomem(struct fb_info *info)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +	struct drm_client_buffer *buffer = fb_helper->buffer;
> +
> +	return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;
> +}
> +
> +static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_t count, 
> +				   loff_t pos)
The naming here confused me - a name like:
fb_read_iomem() would have helped me more.
With the current naming I shall remember that the screen_base member is
the iomem pointer.

> +{
> +	const char __iomem *src = info->screen_base + pos;
> +	size_t alloc_size = min(count, PAGE_SIZE);
> +	ssize_t ret = 0;
> +	char *tmp;
> +
> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
> +	if (!tmp)
> +		return -ENOMEM;
> +

I looked around and could not find other places where
we copy from iomem to mem to usermem in chunks of PAGE_SIZE.

> +	while (count) {
> +		size_t c = min(count, alloc_size);
> +
> +		memcpy_fromio(tmp, src, c);
> +		if (copy_to_user(buf, tmp, c)) {
> +			ret = -EFAULT;
> +			break;
> +		}
> +
> +		src += c;
> +		buf += c;
> +		ret += c;
> +		count -= c;
> +	}
> +
> +	kfree(tmp);
> +
> +	return ret;
> +}
> +
> +static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, size_t count,
> +				     loff_t pos)
And fb_read_sysmem() here.

> +{
> +	const char *src = info->screen_buffer + pos;
> +
> +	if (copy_to_user(buf, src, count))
> +		return -EFAULT;
> +
> +	return count;
> +}
> +
> +static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,
> +				 size_t count, loff_t *ppos)
> +{
> +	loff_t pos = *ppos;
> +	size_t total_size;
> +	ssize_t ret;
> +
> +	if (info->state != FBINFO_STATE_RUNNING)
> +		return -EPERM;
> +
> +	if (info->screen_size)
> +		total_size = info->screen_size;
> +	else
> +		total_size = info->fix.smem_len;
> +
> +	if (pos >= total_size)
> +		return 0;
> +	if (count >= total_size)
> +		count = total_size;
> +	if (total_size - count < pos)
> +		count = total_size - pos;
> +
> +	if (drm_fbdev_use_iomem(info))
> +		ret = fb_read_screen_base(info, buf, count, pos);
> +	else
> +		ret = fb_read_screen_buffer(info, buf, count, pos);
> +
> +	if (ret > 0)
> +		*ppos = ret;
> +
> +	return ret;
> +}
> +
> +static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf, size_t count,
> +				    loff_t pos)

fb_write_iomem()

> +{
> +	char __iomem *dst = info->screen_base + pos;
> +	size_t alloc_size = min(count, PAGE_SIZE);
> +	ssize_t ret = 0;
> +	u8 *tmp;
> +
> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
> +	if (!tmp)
> +		return -ENOMEM;
> +
> +	while (count) {
> +		size_t c = min(count, alloc_size);
> +
> +		if (copy_from_user(tmp, buf, c)) {
> +			ret = -EFAULT;
> +			break;
> +		}
> +		memcpy_toio(dst, tmp, c);
> +
> +		dst += c;
> +		buf += c;
> +		ret += c;
> +		count -= c;
> +	}
> +
> +	kfree(tmp);
> +
> +	return ret;
> +}
> +
> +static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user *buf, size_t count,
> +				      loff_t pos)
fb_write_sysmem()

> +{
> +	char *dst = info->screen_buffer + pos;
> +
> +	if (copy_from_user(dst, buf, count))
> +		return -EFAULT;
> +
> +	return count;
> +}
> +
> +static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
> +				  size_t count, loff_t *ppos)
> +{
> +	loff_t pos = *ppos;
> +	size_t total_size;
> +	ssize_t ret;
> +	int err;
> +
> +	if (info->state != FBINFO_STATE_RUNNING)
> +		return -EPERM;
> +
> +	if (info->screen_size)
> +		total_size = info->screen_size;
> +	else
> +		total_size = info->fix.smem_len;
> +
> +	if (pos > total_size)
> +		return -EFBIG;
> +	if (count > total_size) {
> +		err = -EFBIG;
> +		count = total_size;
> +	}
> +	if (total_size - count < pos) {
> +		if (!err)
> +			err = -ENOSPC;
> +		count = total_size - pos;
> +	}
> +
> +	/*
> +	 * Copy to framebuffer even if we already logged an error. Emulates
> +	 * the behavior of the original fbdev implementation.
> +	 */
> +	if (drm_fbdev_use_iomem(info))
> +		ret = fb_write_screen_base(info, buf, count, pos);
> +	else
> +		ret = fb_write_screen_buffer(info, buf, count, pos);
> +
> +	if (ret > 0)
> +		*ppos = ret;
> +
> +	if (err)
> +		return err;
> +
> +	return ret;
> +}
> +
> +static void drm_fbdev_fb_fillrect(struct fb_info *info,
> +				  const struct fb_fillrect *rect)
> +{
> +	if (drm_fbdev_use_iomem(info))
> +		drm_fb_helper_cfb_fillrect(info, rect);
> +	else
> +		drm_fb_helper_sys_fillrect(info, rect);
> +}
> +
> +static void drm_fbdev_fb_copyarea(struct fb_info *info,
> +				  const struct fb_copyarea *area)
> +{
> +	if (drm_fbdev_use_iomem(info))
> +		drm_fb_helper_cfb_copyarea(info, area);
> +	else
> +		drm_fb_helper_sys_copyarea(info, area);
> +}
> +
> +static void drm_fbdev_fb_imageblit(struct fb_info *info,
> +				   const struct fb_image *image)
> +{
> +	if (drm_fbdev_use_iomem(info))
> +		drm_fb_helper_cfb_imageblit(info, image);
> +	else
> +		drm_fb_helper_sys_imageblit(info, image);
> +}
> +
>  static const struct fb_ops drm_fbdev_fb_ops = {
>  	.owner		= THIS_MODULE,
>  	DRM_FB_HELPER_DEFAULT_OPS,
> @@ -2034,11 +2233,11 @@ static const struct fb_ops drm_fbdev_fb_ops = {
>  	.fb_release	= drm_fbdev_fb_release,
>  	.fb_destroy	= drm_fbdev_fb_destroy,
>  	.fb_mmap	= drm_fbdev_fb_mmap,
> -	.fb_read	= drm_fb_helper_sys_read,
> -	.fb_write	= drm_fb_helper_sys_write,
> -	.fb_fillrect	= drm_fb_helper_sys_fillrect,
> -	.fb_copyarea	= drm_fb_helper_sys_copyarea,
> -	.fb_imageblit	= drm_fb_helper_sys_imageblit,
> +	.fb_read	= drm_fbdev_fb_read,
> +	.fb_write	= drm_fbdev_fb_write,
> +	.fb_fillrect	= drm_fbdev_fb_fillrect,
> +	.fb_copyarea	= drm_fbdev_fb_copyarea,
> +	.fb_imageblit	= drm_fbdev_fb_imageblit,
>  };
>  
>  static struct fb_deferred_io drm_fbdev_defio = {
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index 5ffbb4ed5b35..ab424ddd7665 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -877,18 +877,6 @@ struct drm_mode_config {
>  	 */
>  	bool prefer_shadow_fbdev;
>  
> -	/**
> -	 * @fbdev_use_iomem:
> -	 *
> -	 * Set to true if framebuffer reside in iomem.
> -	 * When set to true memcpy_toio() is used when copying the framebuffer in
> -	 * drm_fb_helper.drm_fb_helper_dirty_blit_real().
> -	 *
> -	 * FIXME: This should be replaced with a per-mapping is_iomem
> -	 * flag (like ttm does), and then used everywhere in fbdev code.
> -	 */
> -	bool fbdev_use_iomem;
> -
>  	/**
>  	 * @quirk_addfb_prefer_xbgr_30bpp:
>  	 *
> -- 
> 2.28.0

Thomas Zimmermann Oct. 26, 2020, 7:50 a.m. UTC | #5

Hi

Am 24.10.20 um 22:38 schrieb Sam Ravnborg:
> Hi Thomas.
> 
> On Tue, Oct 20, 2020 at 02:20:46PM +0200, Thomas Zimmermann wrote:
>> At least sparc64 requires I/O-specific access to framebuffers. This
>> patch updates the fbdev console accordingly.
>>
>> For drivers with direct access to the framebuffer memory, the callback
>> functions in struct fb_ops test for the type of memory and call the rsp
>> fb_sys_ of fb_cfb_ functions. Read and write operations are implemented
>> internally by DRM's fbdev helper.
>>
>> For drivers that employ a shadow buffer, fbdev's blit function retrieves
>> the framebuffer address as struct dma_buf_map, and uses dma_buf_map
>> interfaces to access the buffer.
>>
>> The bochs driver on sparc64 uses a workaround to flag the framebuffer as
>> I/O memory and avoid a HW exception. With the introduction of struct
>> dma_buf_map, this is not required any longer. The patch removes the rsp
>> code from both, bochs and fbdev.
>>
>> v5:
>> 	* implement fb_read/fb_write internally (Daniel, Sam)
>> v4:
>> 	* move dma_buf_map changes into separate patch (Daniel)
>> 	* TODO list: comment on fbdev updates (Daniel)
>>
>> Signed-off-by: Thomas Zimmermann <[e-mail]>
>> Tested-by: Sam Ravnborg <[e-mail]>
> Reviewed-by: Sam Ravnborg <[e-mail]>
> 
> But see a few comments below on naming for you to consider.
> 
> 	Sam
> 
>> ---
>>  Documentation/gpu/todo.rst        |  19 ++-
>>  drivers/gpu/drm/bochs/bochs_kms.c |   1 -
>>  drivers/gpu/drm/drm_fb_helper.c   | 227 ++++++++++++++++++++++++++++--
>>  include/drm/drm_mode_config.h     |  12 --
>>  4 files changed, 230 insertions(+), 29 deletions(-)
>>
>> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
>> index 7e6fc3c04add..638b7f704339 100644
>> --- a/Documentation/gpu/todo.rst
>> +++ b/Documentation/gpu/todo.rst
>> @@ -197,13 +197,28 @@ Convert drivers to use drm_fbdev_generic_setup()
>>  ------------------------------------------------
>>  
>>  Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
>> -atomic modesetting and GEM vmap support. Current generic fbdev emulation
>> -expects the framebuffer in system memory (or system-like memory).
>> +atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
>> +expected the framebuffer in system memory or system-like memory. By employing
>> +struct dma_buf_map, drivers with frambuffers in I/O memory can be supported
>> +as well.
>>  
>>  Contact: Maintainer of the driver you plan to convert
>>  
>>  Level: Intermediate
>>  
>> +Reimplement functions in drm_fbdev_fb_ops without fbdev
>> +-------------------------------------------------------
>> +
>> +A number of callback functions in drm_fbdev_fb_ops could benefit from
>> +being rewritten without dependencies on the fbdev module. Some of the
>> +helpers could further benefit from using struct dma_buf_map instead of
>> +raw pointers.
>> +
>> +Contact: Thomas Zimmermann <[e-mail]>, Daniel Vetter
>> +
>> +Level: Advanced
>> +
>> +
>>  drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
>>  -----------------------------------------------------------------
>>  
>> diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c
>> index 13d0d04c4457..853081d186d5 100644
>> --- a/drivers/gpu/drm/bochs/bochs_kms.c
>> +++ b/drivers/gpu/drm/bochs/bochs_kms.c
>> @@ -151,7 +151,6 @@ int bochs_kms_init(struct bochs_device *bochs)
>>  	bochs->dev->mode_config.preferred_depth = 24;
>>  	bochs->dev->mode_config.prefer_shadow = 0;
>>  	bochs->dev->mode_config.prefer_shadow_fbdev = 1;
>> -	bochs->dev->mode_config.fbdev_use_iomem = true;
>>  	bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;
>>  
>>  	bochs->dev->mode_config.funcs = &bochs_mode_funcs;
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 6212cd7cde1d..1d3180841778 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -372,24 +372,22 @@ static void drm_fb_helper_resume_worker(struct work_struct *work)
>>  }
>>  
>>  static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
>> -					  struct drm_clip_rect *clip)
>> +					  struct drm_clip_rect *clip,
>> +					  struct dma_buf_map *dst)
>>  {
>>  	struct drm_framebuffer *fb = fb_helper->fb;
>>  	unsigned int cpp = fb->format->cpp[0];
>>  	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
>>  	void *src = fb_helper->fbdev->screen_buffer + offset;
>> -	void *dst = fb_helper->buffer->map.vaddr + offset;
>>  	size_t len = (clip->x2 - clip->x1) * cpp;
>>  	unsigned int y;
>>  
>> -	for (y = clip->y1; y < clip->y2; y++) {
>> -		if (!fb_helper->dev->mode_config.fbdev_use_iomem)
>> -			memcpy(dst, src, len);
>> -		else
>> -			memcpy_toio((void __iomem *)dst, src, len);
>> +	dma_buf_map_incr(dst, offset); /* go to first pixel within clip rect */
>>  
>> +	for (y = clip->y1; y < clip->y2; y++) {
>> +		dma_buf_map_memcpy_to(dst, src, len);
>> +		dma_buf_map_incr(dst, fb->pitches[0]);
>>  		src += fb->pitches[0];
>> -		dst += fb->pitches[0];
>>  	}
>>  }
>>  
>> @@ -417,8 +415,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
>>  			ret = drm_client_buffer_vmap(helper->buffer, &map);
>>  			if (ret)
>>  				return;
>> -			drm_fb_helper_dirty_blit_real(helper, &clip_copy);
>> +			drm_fb_helper_dirty_blit_real(helper, &clip_copy, &map);
>>  		}
>> +
>>  		if (helper->fb->funcs->dirty)
>>  			helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,
>>  						 &clip_copy, 1);
>> @@ -2027,6 +2026,206 @@ static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
>>  		return -ENODEV;
>>  }
>>  
>> +static bool drm_fbdev_use_iomem(struct fb_info *info)
>> +{
>> +	struct drm_fb_helper *fb_helper = info->par;
>> +	struct drm_client_buffer *buffer = fb_helper->buffer;
>> +
>> +	return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;
>> +}
>> +
>> +static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_t count, 
>> +				   loff_t pos)
> The naming here confused me - a name like:
> fb_read_iomem() would have helped me more.
> With the current naming I shall remember that the screen_base member is
> the iomem pointer.

Yeah, true. In terms of naming, I was undecided. I was thinking about
adopting a naming similar to what you describe, but OTOH we don't use
sysmem anywhere in the code. I thought about adopting fbdev's conention
of using _sys_ and _cfb_. But that would make sensein the local context.

> 
>> +{
>> +	const char __iomem *src = info->screen_base + pos;
>> +	size_t alloc_size = min(count, PAGE_SIZE);
>> +	ssize_t ret = 0;
>> +	char *tmp;
>> +
>> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
>> +	if (!tmp)
>> +		return -ENOMEM;
>> +
> 
> I looked around and could not find other places where
> we copy from iomem to mem to usermem in chunks of PAGE_SIZE.

I took this pattern from fbdev's original implementation. I think it's
done to work nicely with kmalloc.

Best regards
Thomas

> 
>> +	while (count) {
>> +		size_t c = min(count, alloc_size);
>> +
>> +		memcpy_fromio(tmp, src, c);
>> +		if (copy_to_user(buf, tmp, c)) {
>> +			ret = -EFAULT;
>> +			break;
>> +		}
>> +
>> +		src += c;
>> +		buf += c;
>> +		ret += c;
>> +		count -= c;
>> +	}
>> +
>> +	kfree(tmp);
>> +
>> +	return ret;
>> +}
>> +
>> +static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, size_t count,
>> +				     loff_t pos)
> And fb_read_sysmem() here.
> 
>> +{
>> +	const char *src = info->screen_buffer + pos;
>> +
>> +	if (copy_to_user(buf, src, count))
>> +		return -EFAULT;
>> +
>> +	return count;
>> +}
>> +
>> +static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,
>> +				 size_t count, loff_t *ppos)
>> +{
>> +	loff_t pos = *ppos;
>> +	size_t total_size;
>> +	ssize_t ret;
>> +
>> +	if (info->state != FBINFO_STATE_RUNNING)
>> +		return -EPERM;
>> +
>> +	if (info->screen_size)
>> +		total_size = info->screen_size;
>> +	else
>> +		total_size = info->fix.smem_len;
>> +
>> +	if (pos >= total_size)
>> +		return 0;
>> +	if (count >= total_size)
>> +		count = total_size;
>> +	if (total_size - count < pos)
>> +		count = total_size - pos;
>> +
>> +	if (drm_fbdev_use_iomem(info))
>> +		ret = fb_read_screen_base(info, buf, count, pos);
>> +	else
>> +		ret = fb_read_screen_buffer(info, buf, count, pos);
>> +
>> +	if (ret > 0)
>> +		*ppos = ret;
>> +
>> +	return ret;
>> +}
>> +
>> +static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf, size_t count,
>> +				    loff_t pos)
> 
> fb_write_iomem()
> 
>> +{
>> +	char __iomem *dst = info->screen_base + pos;
>> +	size_t alloc_size = min(count, PAGE_SIZE);
>> +	ssize_t ret = 0;
>> +	u8 *tmp;
>> +
>> +	tmp = kmalloc(alloc_size, GFP_KERNEL);
>> +	if (!tmp)
>> +		return -ENOMEM;
>> +
>> +	while (count) {
>> +		size_t c = min(count, alloc_size);
>> +
>> +		if (copy_from_user(tmp, buf, c)) {
>> +			ret = -EFAULT;
>> +			break;
>> +		}
>> +		memcpy_toio(dst, tmp, c);
>> +
>> +		dst += c;
>> +		buf += c;
>> +		ret += c;
>> +		count -= c;
>> +	}
>> +
>> +	kfree(tmp);
>> +
>> +	return ret;
>> +}
>> +
>> +static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user *buf, size_t count,
>> +				      loff_t pos)
> fb_write_sysmem()
> 
>> +{
>> +	char *dst = info->screen_buffer + pos;
>> +
>> +	if (copy_from_user(dst, buf, count))
>> +		return -EFAULT;
>> +
>> +	return count;
>> +}
>> +
>> +static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
>> +				  size_t count, loff_t *ppos)
>> +{
>> +	loff_t pos = *ppos;
>> +	size_t total_size;
>> +	ssize_t ret;
>> +	int err;
>> +
>> +	if (info->state != FBINFO_STATE_RUNNING)
>> +		return -EPERM;
>> +
>> +	if (info->screen_size)
>> +		total_size = info->screen_size;
>> +	else
>> +		total_size = info->fix.smem_len;
>> +
>> +	if (pos > total_size)
>> +		return -EFBIG;
>> +	if (count > total_size) {
>> +		err = -EFBIG;
>> +		count = total_size;
>> +	}
>> +	if (total_size - count < pos) {
>> +		if (!err)
>> +			err = -ENOSPC;
>> +		count = total_size - pos;
>> +	}
>> +
>> +	/*
>> +	 * Copy to framebuffer even if we already logged an error. Emulates
>> +	 * the behavior of the original fbdev implementation.
>> +	 */
>> +	if (drm_fbdev_use_iomem(info))
>> +		ret = fb_write_screen_base(info, buf, count, pos);
>> +	else
>> +		ret = fb_write_screen_buffer(info, buf, count, pos);
>> +
>> +	if (ret > 0)
>> +		*ppos = ret;
>> +
>> +	if (err)
>> +		return err;
>> +
>> +	return ret;
>> +}
>> +
>> +static void drm_fbdev_fb_fillrect(struct fb_info *info,
>> +				  const struct fb_fillrect *rect)
>> +{
>> +	if (drm_fbdev_use_iomem(info))
>> +		drm_fb_helper_cfb_fillrect(info, rect);
>> +	else
>> +		drm_fb_helper_sys_fillrect(info, rect);
>> +}
>> +
>> +static void drm_fbdev_fb_copyarea(struct fb_info *info,
>> +				  const struct fb_copyarea *area)
>> +{
>> +	if (drm_fbdev_use_iomem(info))
>> +		drm_fb_helper_cfb_copyarea(info, area);
>> +	else
>> +		drm_fb_helper_sys_copyarea(info, area);
>> +}
>> +
>> +static void drm_fbdev_fb_imageblit(struct fb_info *info,
>> +				   const struct fb_image *image)
>> +{
>> +	if (drm_fbdev_use_iomem(info))
>> +		drm_fb_helper_cfb_imageblit(info, image);
>> +	else
>> +		drm_fb_helper_sys_imageblit(info, image);
>> +}
>> +
>>  static const struct fb_ops drm_fbdev_fb_ops = {
>>  	.owner		= THIS_MODULE,
>>  	DRM_FB_HELPER_DEFAULT_OPS,
>> @@ -2034,11 +2233,11 @@ static const struct fb_ops drm_fbdev_fb_ops = {
>>  	.fb_release	= drm_fbdev_fb_release,
>>  	.fb_destroy	= drm_fbdev_fb_destroy,
>>  	.fb_mmap	= drm_fbdev_fb_mmap,
>> -	.fb_read	= drm_fb_helper_sys_read,
>> -	.fb_write	= drm_fb_helper_sys_write,
>> -	.fb_fillrect	= drm_fb_helper_sys_fillrect,
>> -	.fb_copyarea	= drm_fb_helper_sys_copyarea,
>> -	.fb_imageblit	= drm_fb_helper_sys_imageblit,
>> +	.fb_read	= drm_fbdev_fb_read,
>> +	.fb_write	= drm_fbdev_fb_write,
>> +	.fb_fillrect	= drm_fbdev_fb_fillrect,
>> +	.fb_copyarea	= drm_fbdev_fb_copyarea,
>> +	.fb_imageblit	= drm_fbdev_fb_imageblit,
>>  };
>>  
>>  static struct fb_deferred_io drm_fbdev_defio = {
>> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
>> index 5ffbb4ed5b35..ab424ddd7665 100644
>> --- a/include/drm/drm_mode_config.h
>> +++ b/include/drm/drm_mode_config.h
>> @@ -877,18 +877,6 @@ struct drm_mode_config {
>>  	 */
>>  	bool prefer_shadow_fbdev;
>>  
>> -	/**
>> -	 * @fbdev_use_iomem:
>> -	 *
>> -	 * Set to true if framebuffer reside in iomem.
>> -	 * When set to true memcpy_toio() is used when copying the framebuffer in
>> -	 * drm_fb_helper.drm_fb_helper_dirty_blit_real().
>> -	 *
>> -	 * FIXME: This should be replaced with a per-mapping is_iomem
>> -	 * flag (like ttm does), and then used everywhere in fbdev code.
>> -	 */
>> -	bool fbdev_use_iomem;
>> -
>>  	/**
>>  	 * @quirk_addfb_prefer_xbgr_30bpp:
>>  	 *
>> -- 
>> 2.28.0
> _______________________________________________
> dri-devel mailing list
> [e-mail]
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>

Patch

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 7e6fc3c04add..638b7f704339 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -197,13 +197,28 @@  Convert drivers to use drm_fbdev_generic_setup()
 ------------------------------------------------
 
 Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
-atomic modesetting and GEM vmap support. Current generic fbdev emulation
-expects the framebuffer in system memory (or system-like memory).
+atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
+expected the framebuffer in system memory or system-like memory. By employing
+struct dma_buf_map, drivers with frambuffers in I/O memory can be supported
+as well.
 
 Contact: Maintainer of the driver you plan to convert
 
 Level: Intermediate
 
+Reimplement functions in drm_fbdev_fb_ops without fbdev
+-------------------------------------------------------
+
+A number of callback functions in drm_fbdev_fb_ops could benefit from
+being rewritten without dependencies on the fbdev module. Some of the
+helpers could further benefit from using struct dma_buf_map instead of
+raw pointers.
+
+Contact: Thomas Zimmermann <[e-mail]>, Daniel Vetter
+
+Level: Advanced
+
+
 drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
 -----------------------------------------------------------------
 
diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c
index 13d0d04c4457..853081d186d5 100644
--- a/drivers/gpu/drm/bochs/bochs_kms.c
+++ b/drivers/gpu/drm/bochs/bochs_kms.c
@@ -151,7 +151,6 @@  int bochs_kms_init(struct bochs_device *bochs)
 	bochs->dev->mode_config.preferred_depth = 24;
 	bochs->dev->mode_config.prefer_shadow = 0;
 	bochs->dev->mode_config.prefer_shadow_fbdev = 1;
-	bochs->dev->mode_config.fbdev_use_iomem = true;
 	bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;
 
 	bochs->dev->mode_config.funcs = &bochs_mode_funcs;
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 6212cd7cde1d..1d3180841778 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -372,24 +372,22 @@  static void drm_fb_helper_resume_worker(struct work_struct *work)
 }
 
 static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
-					  struct drm_clip_rect *clip)
+					  struct drm_clip_rect *clip,
+					  struct dma_buf_map *dst)
 {
 	struct drm_framebuffer *fb = fb_helper->fb;
 	unsigned int cpp = fb->format->cpp[0];
 	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
 	void *src = fb_helper->fbdev->screen_buffer + offset;
-	void *dst = fb_helper->buffer->map.vaddr + offset;
 	size_t len = (clip->x2 - clip->x1) * cpp;
 	unsigned int y;
 
-	for (y = clip->y1; y < clip->y2; y++) {
-		if (!fb_helper->dev->mode_config.fbdev_use_iomem)
-			memcpy(dst, src, len);
-		else
-			memcpy_toio((void __iomem *)dst, src, len);
+	dma_buf_map_incr(dst, offset); /* go to first pixel within clip rect */
 
+	for (y = clip->y1; y < clip->y2; y++) {
+		dma_buf_map_memcpy_to(dst, src, len);
+		dma_buf_map_incr(dst, fb->pitches[0]);
 		src += fb->pitches[0];
-		dst += fb->pitches[0];
 	}
 }
 
@@ -417,8 +415,9 @@  static void drm_fb_helper_dirty_work(struct work_struct *work)
 			ret = drm_client_buffer_vmap(helper->buffer, &map);
 			if (ret)
 				return;
-			drm_fb_helper_dirty_blit_real(helper, &clip_copy);
+			drm_fb_helper_dirty_blit_real(helper, &clip_copy, &map);
 		}
+
 		if (helper->fb->funcs->dirty)
 			helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,
 						 &clip_copy, 1);
@@ -2027,6 +2026,206 @@  static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
 		return -ENODEV;
 }
 
+static bool drm_fbdev_use_iomem(struct fb_info *info)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+	struct drm_client_buffer *buffer = fb_helper->buffer;
+
+	return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;
+}
+
+static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_t count, 
+				   loff_t pos)
+{
+	const char __iomem *src = info->screen_base + pos;
+	size_t alloc_size = min(count, PAGE_SIZE);
+	ssize_t ret = 0;
+	char *tmp;
+
+	tmp = kmalloc(alloc_size, GFP_KERNEL);
+	if (!tmp)
+		return -ENOMEM;
+
+	while (count) {
+		size_t c = min(count, alloc_size);
+
+		memcpy_fromio(tmp, src, c);
+		if (copy_to_user(buf, tmp, c)) {
+			ret = -EFAULT;
+			break;
+		}
+
+		src += c;
+		buf += c;
+		ret += c;
+		count -= c;
+	}
+
+	kfree(tmp);
+
+	return ret;
+}
+
+static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, size_t count,
+				     loff_t pos)
+{
+	const char *src = info->screen_buffer + pos;
+
+	if (copy_to_user(buf, src, count))
+		return -EFAULT;
+
+	return count;
+}
+
+static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,
+				 size_t count, loff_t *ppos)
+{
+	loff_t pos = *ppos;
+	size_t total_size;
+	ssize_t ret;
+
+	if (info->state != FBINFO_STATE_RUNNING)
+		return -EPERM;
+
+	if (info->screen_size)
+		total_size = info->screen_size;
+	else
+		total_size = info->fix.smem_len;
+
+	if (pos >= total_size)
+		return 0;
+	if (count >= total_size)
+		count = total_size;
+	if (total_size - count < pos)
+		count = total_size - pos;
+
+	if (drm_fbdev_use_iomem(info))
+		ret = fb_read_screen_base(info, buf, count, pos);
+	else
+		ret = fb_read_screen_buffer(info, buf, count, pos);
+
+	if (ret > 0)
+		*ppos = ret;
+
+	return ret;
+}
+
+static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf, size_t count,
+				    loff_t pos)
+{
+	char __iomem *dst = info->screen_base + pos;
+	size_t alloc_size = min(count, PAGE_SIZE);
+	ssize_t ret = 0;
+	u8 *tmp;
+
+	tmp = kmalloc(alloc_size, GFP_KERNEL);
+	if (!tmp)
+		return -ENOMEM;
+
+	while (count) {
+		size_t c = min(count, alloc_size);
+
+		if (copy_from_user(tmp, buf, c)) {
+			ret = -EFAULT;
+			break;
+		}
+		memcpy_toio(dst, tmp, c);
+
+		dst += c;
+		buf += c;
+		ret += c;
+		count -= c;
+	}
+
+	kfree(tmp);
+
+	return ret;
+}
+
+static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user *buf, size_t count,
+				      loff_t pos)
+{
+	char *dst = info->screen_buffer + pos;
+
+	if (copy_from_user(dst, buf, count))
+		return -EFAULT;
+
+	return count;
+}
+
+static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
+				  size_t count, loff_t *ppos)
+{
+	loff_t pos = *ppos;
+	size_t total_size;
+	ssize_t ret;
+	int err;
+
+	if (info->state != FBINFO_STATE_RUNNING)
+		return -EPERM;
+
+	if (info->screen_size)
+		total_size = info->screen_size;
+	else
+		total_size = info->fix.smem_len;
+
+	if (pos > total_size)
+		return -EFBIG;
+	if (count > total_size) {
+		err = -EFBIG;
+		count = total_size;
+	}
+	if (total_size - count < pos) {
+		if (!err)
+			err = -ENOSPC;
+		count = total_size - pos;
+	}
+
+	/*
+	 * Copy to framebuffer even if we already logged an error. Emulates
+	 * the behavior of the original fbdev implementation.
+	 */
+	if (drm_fbdev_use_iomem(info))
+		ret = fb_write_screen_base(info, buf, count, pos);
+	else
+		ret = fb_write_screen_buffer(info, buf, count, pos);
+
+	if (ret > 0)
+		*ppos = ret;
+
+	if (err)
+		return err;
+
+	return ret;
+}
+
+static void drm_fbdev_fb_fillrect(struct fb_info *info,
+				  const struct fb_fillrect *rect)
+{
+	if (drm_fbdev_use_iomem(info))
+		drm_fb_helper_cfb_fillrect(info, rect);
+	else
+		drm_fb_helper_sys_fillrect(info, rect);
+}
+
+static void drm_fbdev_fb_copyarea(struct fb_info *info,
+				  const struct fb_copyarea *area)
+{
+	if (drm_fbdev_use_iomem(info))
+		drm_fb_helper_cfb_copyarea(info, area);
+	else
+		drm_fb_helper_sys_copyarea(info, area);
+}
+
+static void drm_fbdev_fb_imageblit(struct fb_info *info,
+				   const struct fb_image *image)
+{
+	if (drm_fbdev_use_iomem(info))
+		drm_fb_helper_cfb_imageblit(info, image);
+	else
+		drm_fb_helper_sys_imageblit(info, image);
+}
+
 static const struct fb_ops drm_fbdev_fb_ops = {
 	.owner		= THIS_MODULE,
 	DRM_FB_HELPER_DEFAULT_OPS,
@@ -2034,11 +2233,11 @@  static const struct fb_ops drm_fbdev_fb_ops = {
 	.fb_release	= drm_fbdev_fb_release,
 	.fb_destroy	= drm_fbdev_fb_destroy,
 	.fb_mmap	= drm_fbdev_fb_mmap,
-	.fb_read	= drm_fb_helper_sys_read,
-	.fb_write	= drm_fb_helper_sys_write,
-	.fb_fillrect	= drm_fb_helper_sys_fillrect,
-	.fb_copyarea	= drm_fb_helper_sys_copyarea,
-	.fb_imageblit	= drm_fb_helper_sys_imageblit,
+	.fb_read	= drm_fbdev_fb_read,
+	.fb_write	= drm_fbdev_fb_write,
+	.fb_fillrect	= drm_fbdev_fb_fillrect,
+	.fb_copyarea	= drm_fbdev_fb_copyarea,
+	.fb_imageblit	= drm_fbdev_fb_imageblit,
 };
 
 static struct fb_deferred_io drm_fbdev_defio = {
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index 5ffbb4ed5b35..ab424ddd7665 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -877,18 +877,6 @@  struct drm_mode_config {
 	 */
 	bool prefer_shadow_fbdev;
 
-	/**
-	 * @fbdev_use_iomem:
-	 *
-	 * Set to true if framebuffer reside in iomem.
-	 * When set to true memcpy_toio() is used when copying the framebuffer in
-	 * drm_fb_helper.drm_fb_helper_dirty_blit_real().
-	 *
-	 * FIXME: This should be replaced with a per-mapping is_iomem
-	 * flag (like ttm does), and then used everywhere in fbdev code.
-	 */
-	bool fbdev_use_iomem;
-
 	/**
 	 * @quirk_addfb_prefer_xbgr_30bpp:
 	 *