[1/6] drm/rockchip: import dma_buf to gem
diff mbox

Message ID 1434613770-6608-2-git-send-email-mark.yao@rock-chips.com
State New
Headers show

Commit Message

yao mark June 18, 2015, 7:49 a.m. UTC
We want to display a buffer allocated by other driver, need import
the buffer to gem.

Signed-off-by: Mark Yao <mark.yao@rock-chips.com>
---
 drivers/gpu/drm/rockchip/rockchip_drm_drv.c |    1 +
 drivers/gpu/drm/rockchip/rockchip_drm_gem.c |   45 +++++++++++++++++++++++++--
 drivers/gpu/drm/rockchip/rockchip_drm_gem.h |    5 ++-
 3 files changed, 47 insertions(+), 4 deletions(-)

Comments

Russell King - ARM Linux June 18, 2015, 10:57 a.m. UTC | #1
On Thu, Jun 18, 2015 at 03:49:25PM +0800, Mark Yao wrote:
> We want to display a buffer allocated by other driver, need import
> the buffer to gem.
> 
> Signed-off-by: Mark Yao <mark.yao@rock-chips.com>
> ---
>  drivers/gpu/drm/rockchip/rockchip_drm_drv.c |    1 +
>  drivers/gpu/drm/rockchip/rockchip_drm_gem.c |   45 +++++++++++++++++++++++++--
>  drivers/gpu/drm/rockchip/rockchip_drm_gem.h |    5 ++-
>  3 files changed, 47 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> index 3962176..9001a90 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> @@ -287,6 +287,7 @@ static struct drm_driver rockchip_drm_driver = {
>  	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd,
>  	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle,
>  	.gem_prime_import	= drm_gem_prime_import,
> +	.gem_prime_import_sg_table = rockchip_gem_prime_import_sg_table,
>  	.gem_prime_export	= drm_gem_prime_export,
>  	.gem_prime_get_sg_table	= rockchip_gem_prime_get_sg_table,
>  	.gem_prime_vmap		= rockchip_gem_prime_vmap,
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> index eb2282c..2e30e23 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> @@ -18,6 +18,7 @@
>  #include <drm/drm_vma_manager.h>
>  
>  #include <linux/dma-attrs.h>
> +#include <linux/dma-buf.h>
>  
>  #include "rockchip_drm_drv.h"
>  #include "rockchip_drm_gem.h"
> @@ -105,6 +106,38 @@ int rockchip_gem_mmap(struct file *filp, struct vm_area_struct *vma)
>  	return ret;
>  }
>  
> +struct drm_gem_object *
> +rockchip_gem_prime_import_sg_table(struct drm_device *drm,
> +				   struct dma_buf_attachment *attach,
> +				   struct sg_table *sgt)
> +{
> +	struct rockchip_gem_object *rk_obj;
> +	struct drm_gem_object *obj;
> +	int ret;
> +
> +	rk_obj = kzalloc(sizeof(*rk_obj), GFP_KERNEL);
> +	if (!rk_obj)
> +		return ERR_PTR(-ENOMEM);
> +
> +	obj = &rk_obj->base;
> +
> +	drm_gem_private_object_init(drm, obj, attach->dmabuf->size);
> +
> +	if (!dma_map_sg(drm->dev, sgt->sgl, sgt->nents, DMA_TO_DEVICE)) {
> +		ret = -ENOMEM;
> +		goto err_free_obj;
> +	}
> +	rk_obj->dma_addr = sg_dma_address(sgt->sgl);
> +	rk_obj->sgt = sgt;
> +	obj->size = sg_dma_len(sgt->sgl);

This is wrong.

First, if you can only cope with a single scatterlist entry, you need to
enforce that.  You can do that in your gem_prime_import_sg_table() method
by checking sgt->nents.

Secondly, you're mapping an already mapped scatterlist - scatterlists
are mapped by the exporter inside dma_buf_map_attachment() for your
device.

Thirdly, I hate drm_gem_prime_import() being used on ARM... it forces
drivers to do something very buggy: the DMA buffer is mapped for DMA
when the buffer is imported.  If the buffer is a write-combine or cached
buffer, writes to the buffer after the import will not become visible to
the display hardware until sometime later (when they're evicted from the
caches and/or pushed out of the bus structure.)  The DMA mapping should
be performed as close to the start of DMA as possible.  However, this is
a long-standing issue I have with dma_buf itself and is not something you
should be too concerned with in your patch.  Just bear it in mind if you
start to see corruption of imported buffers - the answer is not more
dma_map_sg() calls, but to get dma_buf fixed.
yao mark June 19, 2015, 2:50 a.m. UTC | #2
Thanks Russell
On 2015?06?18? 18:57, Russell King - ARM Linux wrote:
> This is wrong.
>
> First, if you can only cope with a single scatterlist entry, you need to
> enforce that.  You can do that in your gem_prime_import_sg_table() method
> by checking sgt->nents.
I'm confuse that how to get coherent iova address from nocoherent 
scatterlist with iommu.
I saw the arm_iommu_map_sg, it says that:
         The scatter gather list elements are merged together (if 
possible) and
          tagged with the appropriate dma address and length.

I guess the map_sg maybe merge scatterlist into coherent iova address, 
but I don't know how to
check the "if possible", and the sgt->nents not be 1 when already map to 
coherent iova address.

checking sgt-nents = 1 can sure that iova is coherent, but when coherent 
iova address from
nocoherent scatterlist, I think sgt->nents maybe greater than 1, is 
there a method can deal it?

All above is my guess, maybe wrong, I only tested it with CMA buffer import.

> Secondly, you're mapping an already mapped scatterlist - scatterlists
> are mapped by the exporter inside dma_buf_map_attachment() for your
> device.

Right, found the dma_map_sg on dma_buf_map_attachment().

>
> Thirdly, I hate drm_gem_prime_import() being used on ARM... it forces
> drivers to do something very buggy: the DMA buffer is mapped for DMA
> when the buffer is imported.  If the buffer is a write-combine or cached
> buffer, writes to the buffer after the import will not become visible to
> the display hardware until sometime later (when they're evicted from the
> caches and/or pushed out of the bus structure.)  The DMA mapping should
> be performed as close to the start of DMA as possible.  However, this is
> a long-standing issue I have with dma_buf itself and is not something you
> should be too concerned with in your patch.  Just bear it in mind if you
> start to see corruption of imported buffers - the answer is not more
> dma_map_sg() calls, but to get dma_buf fixed.
Yeah, Got it.

Patch
diff mbox

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index 3962176..9001a90 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -287,6 +287,7 @@  static struct drm_driver rockchip_drm_driver = {
 	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd,
 	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle,
 	.gem_prime_import	= drm_gem_prime_import,
+	.gem_prime_import_sg_table = rockchip_gem_prime_import_sg_table,
 	.gem_prime_export	= drm_gem_prime_export,
 	.gem_prime_get_sg_table	= rockchip_gem_prime_get_sg_table,
 	.gem_prime_vmap		= rockchip_gem_prime_vmap,
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
index eb2282c..2e30e23 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
@@ -18,6 +18,7 @@ 
 #include <drm/drm_vma_manager.h>
 
 #include <linux/dma-attrs.h>
+#include <linux/dma-buf.h>
 
 #include "rockchip_drm_drv.h"
 #include "rockchip_drm_gem.h"
@@ -105,6 +106,38 @@  int rockchip_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 	return ret;
 }
 
+struct drm_gem_object *
+rockchip_gem_prime_import_sg_table(struct drm_device *drm,
+				   struct dma_buf_attachment *attach,
+				   struct sg_table *sgt)
+{
+	struct rockchip_gem_object *rk_obj;
+	struct drm_gem_object *obj;
+	int ret;
+
+	rk_obj = kzalloc(sizeof(*rk_obj), GFP_KERNEL);
+	if (!rk_obj)
+		return ERR_PTR(-ENOMEM);
+
+	obj = &rk_obj->base;
+
+	drm_gem_private_object_init(drm, obj, attach->dmabuf->size);
+
+	if (!dma_map_sg(drm->dev, sgt->sgl, sgt->nents, DMA_TO_DEVICE)) {
+		ret = -ENOMEM;
+		goto err_free_obj;
+	}
+	rk_obj->dma_addr = sg_dma_address(sgt->sgl);
+	rk_obj->sgt = sgt;
+	obj->size = sg_dma_len(sgt->sgl);
+
+	return obj;
+
+err_free_obj:
+	kfree(rk_obj);
+	return ERR_PTR(ret);
+}
+
 struct rockchip_gem_object *
 	rockchip_gem_create_object(struct drm_device *drm, unsigned int size,
 				   bool alloc_kmap)
@@ -140,13 +173,19 @@  err_free_rk_obj:
  */
 void rockchip_gem_free_object(struct drm_gem_object *obj)
 {
+	struct drm_device *drm = obj->dev;
 	struct rockchip_gem_object *rk_obj;
 
-	drm_gem_free_mmap_offset(obj);
-
 	rk_obj = to_rockchip_obj(obj);
 
-	rockchip_gem_free_buf(rk_obj);
+	if (obj->import_attach) {
+		dma_unmap_sg(drm->dev, rk_obj->sgt->sgl,
+			     rk_obj->sgt->nents, DMA_TO_DEVICE);
+		drm_prime_gem_destroy(obj, rk_obj->sgt);
+	} else {
+		drm_gem_free_mmap_offset(obj);
+		rockchip_gem_free_buf(rk_obj);
+	}
 
 	kfree(rk_obj);
 }
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.h b/drivers/gpu/drm/rockchip/rockchip_drm_gem.h
index ad22618..9fd58e3 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.h
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.h
@@ -21,6 +21,7 @@  struct rockchip_gem_object {
 	struct drm_gem_object base;
 	unsigned int flags;
 
+	struct sg_table *sgt;
 	void *kvaddr;
 	dma_addr_t dma_addr;
 	struct dma_attrs dma_attrs;
@@ -28,8 +29,10 @@  struct rockchip_gem_object {
 
 struct sg_table *rockchip_gem_prime_get_sg_table(struct drm_gem_object *obj);
 struct drm_gem_object *
-rockchip_gem_prime_import_sg_table(struct drm_device *dev, size_t size,
+rockchip_gem_prime_import_sg_table(struct drm_device *drm,
+				   struct dma_buf_attachment *attach,
 				   struct sg_table *sgt);
+
 void *rockchip_gem_prime_vmap(struct drm_gem_object *obj);
 void rockchip_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr);