drm/gma500: Fixup fbdev stolen size usage evaluation
diff mbox series

Message ID 20191107153048.843881-1-paul.kocialkowski@bootlin.com
State New
Headers show
Series
  • drm/gma500: Fixup fbdev stolen size usage evaluation
Related show

Commit Message

Paul Kocialkowski Nov. 7, 2019, 3:30 p.m. UTC
psbfb_probe performs an evaluation of the required size from the stolen
GTT memory, but gets it wrong in two distinct ways:
- The resulting size must be page-size-aligned;
- The size to allocate is derived from the surface dimensions, not the fb
  dimensions.

When two connectors are connected with different modes, the smallest will
be stored in the fb dimensions, but the size that needs to be allocated must
match the largest (surface) dimensions. This is what is used in the actual
allocation code.

Fix this by correcting the evaluation to conform to the two points above.
It allows correctly switching to 16bpp when one connector is e.g. 1920x1080
and the other is 1024x768.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
---
 drivers/gpu/drm/gma500/framebuffer.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Patrik Jakobsson Nov. 12, 2019, 10:20 a.m. UTC | #1
On Thu, Nov 7, 2019 at 4:30 PM Paul Kocialkowski
<paul.kocialkowski@bootlin.com> wrote:
>
> psbfb_probe performs an evaluation of the required size from the stolen
> GTT memory, but gets it wrong in two distinct ways:
> - The resulting size must be page-size-aligned;
> - The size to allocate is derived from the surface dimensions, not the fb
>   dimensions.
>
> When two connectors are connected with different modes, the smallest will
> be stored in the fb dimensions, but the size that needs to be allocated must
> match the largest (surface) dimensions. This is what is used in the actual
> allocation code.
>
> Fix this by correcting the evaluation to conform to the two points above.
> It allows correctly switching to 16bpp when one connector is e.g. 1920x1080
> and the other is 1024x768.
>
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> ---
>  drivers/gpu/drm/gma500/framebuffer.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c
> index 218f3bb15276..90237abee088 100644
> --- a/drivers/gpu/drm/gma500/framebuffer.c
> +++ b/drivers/gpu/drm/gma500/framebuffer.c
> @@ -462,6 +462,7 @@ static int psbfb_probe(struct drm_fb_helper *helper,
>                 container_of(helper, struct psb_fbdev, psb_fb_helper);
>         struct drm_device *dev = psb_fbdev->psb_fb_helper.dev;
>         struct drm_psb_private *dev_priv = dev->dev_private;
> +       unsigned int fb_size;
>         int bytespp;
>
>         bytespp = sizes->surface_bpp / 8;
> @@ -471,8 +472,11 @@ static int psbfb_probe(struct drm_fb_helper *helper,
>         /* If the mode will not fit in 32bit then switch to 16bit to get
>            a console on full resolution. The X mode setting server will
>            allocate its own 32bit GEM framebuffer */
> -       if (ALIGN(sizes->fb_width * bytespp, 64) * sizes->fb_height >
> -                       dev_priv->vram_stolen_size) {
> +       fb_size = ALIGN(sizes->surface_width * bytespp, 64) *
> +                 sizes->surface_height;
> +       fb_size = ALIGN(fb_size, PAGE_SIZE);
> +
> +       if (fb_size > dev_priv->vram_stolen_size) {

psb_gtt_alloc_range() already aligns by PAGE_SIZE for us. Looks like
we align a couple of times extra for luck. This needs cleaning up
instead of adding even more aligns.

Your size calculation looks correct and indeed makes my 1024x600 +
1920x1080 setup actually display something, but for some reason I get
an incorrect panning on the smaller screen and stale data on the
surface only visible by the larger CRTC. Any idea what's going on?

>                  sizes->surface_bpp = 16;
>                  sizes->surface_depth = 16;
>          }
> --
> 2.23.0
>
Paul Kocialkowski Nov. 12, 2019, 3:11 p.m. UTC | #2
Hi,

On Tue 12 Nov 19, 11:20, Patrik Jakobsson wrote:
> On Thu, Nov 7, 2019 at 4:30 PM Paul Kocialkowski
> <paul.kocialkowski@bootlin.com> wrote:
> >
> > psbfb_probe performs an evaluation of the required size from the stolen
> > GTT memory, but gets it wrong in two distinct ways:
> > - The resulting size must be page-size-aligned;
> > - The size to allocate is derived from the surface dimensions, not the fb
> >   dimensions.
> >
> > When two connectors are connected with different modes, the smallest will
> > be stored in the fb dimensions, but the size that needs to be allocated must
> > match the largest (surface) dimensions. This is what is used in the actual
> > allocation code.
> >
> > Fix this by correcting the evaluation to conform to the two points above.
> > It allows correctly switching to 16bpp when one connector is e.g. 1920x1080
> > and the other is 1024x768.
> >
> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> > ---
> >  drivers/gpu/drm/gma500/framebuffer.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c
> > index 218f3bb15276..90237abee088 100644
> > --- a/drivers/gpu/drm/gma500/framebuffer.c
> > +++ b/drivers/gpu/drm/gma500/framebuffer.c
> > @@ -462,6 +462,7 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> >                 container_of(helper, struct psb_fbdev, psb_fb_helper);
> >         struct drm_device *dev = psb_fbdev->psb_fb_helper.dev;
> >         struct drm_psb_private *dev_priv = dev->dev_private;
> > +       unsigned int fb_size;
> >         int bytespp;
> >
> >         bytespp = sizes->surface_bpp / 8;
> > @@ -471,8 +472,11 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> >         /* If the mode will not fit in 32bit then switch to 16bit to get
> >            a console on full resolution. The X mode setting server will
> >            allocate its own 32bit GEM framebuffer */
> > -       if (ALIGN(sizes->fb_width * bytespp, 64) * sizes->fb_height >
> > -                       dev_priv->vram_stolen_size) {
> > +       fb_size = ALIGN(sizes->surface_width * bytespp, 64) *
> > +                 sizes->surface_height;
> > +       fb_size = ALIGN(fb_size, PAGE_SIZE);
> > +
> > +       if (fb_size > dev_priv->vram_stolen_size) {
> 
> psb_gtt_alloc_range() already aligns by PAGE_SIZE for us. Looks like
> we align a couple of times extra for luck. This needs cleaning up
> instead of adding even more aligns.

I'm not sure this is really for luck. As far as I can see, we need to do it
properly for this size estimation since it's the final size that will be
allocated (and thus needs to be available in whole).

For the other times there is explicit alignment, they seem justified too:
- in psb_gem_create: it is common to pass the aligned size when creating the
  associated GEM object with drm_gem_object_init, even though it's probably not
  crucial given that this is not where allocation actually happens;
- in psbfb_create: the full size is apparently only really used to memset 0
  the allocated buffer. I think this makes sense for security reasons (and not
  leak previous contents in the additional space required for alignment).

What strikes me however is that each call to psb_gtt_alloc_range takes the
alignment as a parameter when it's really always PAGE_SIZE, so it should
probably just be hardcoded in the call to allocate_resource.

What do you think?

> Your size calculation looks correct and indeed makes my 1024x600 +
> 1920x1080 setup actually display something, but for some reason I get
> an incorrect panning on the smaller screen and stale data on the
> surface only visible by the larger CRTC. Any idea what's going on?

I'm not seeing this immediately, but I definitely have something strange
after having printed more lines than the smallest display can handle or
scrolling, where more than the actual size of the fb is used.

Maybe this is related to using the PowerVR-accelerated fb ops, that aren't
quite ready for this use case?

I'll give it a try with psbfb_roll_ops and psbfb_unaccel_ops instead to see
if it changes something for me. Maybe it would help for you too?

I suspect that the generic implementation is already bullet-proof for these
kinds of use case.

Cheers and thanks for the feedback,

Paul

> 
> >                  sizes->surface_bpp = 16;
> >                  sizes->surface_depth = 16;
> >          }
> > --
> > 2.23.0
> >
Paul Kocialkowski Nov. 12, 2019, 3:50 p.m. UTC | #3
Hi,

On Tue 12 Nov 19, 16:11, Paul Kocialkowski wrote:
> Hi,
> 
> On Tue 12 Nov 19, 11:20, Patrik Jakobsson wrote:
> > On Thu, Nov 7, 2019 at 4:30 PM Paul Kocialkowski
> > <paul.kocialkowski@bootlin.com> wrote:
> > >
> > > psbfb_probe performs an evaluation of the required size from the stolen
> > > GTT memory, but gets it wrong in two distinct ways:
> > > - The resulting size must be page-size-aligned;
> > > - The size to allocate is derived from the surface dimensions, not the fb
> > >   dimensions.
> > >
> > > When two connectors are connected with different modes, the smallest will
> > > be stored in the fb dimensions, but the size that needs to be allocated must
> > > match the largest (surface) dimensions. This is what is used in the actual
> > > allocation code.
> > >
> > > Fix this by correcting the evaluation to conform to the two points above.
> > > It allows correctly switching to 16bpp when one connector is e.g. 1920x1080
> > > and the other is 1024x768.
> > >
> > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> > > ---
> > >  drivers/gpu/drm/gma500/framebuffer.c | 8 ++++++--
> > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c
> > > index 218f3bb15276..90237abee088 100644
> > > --- a/drivers/gpu/drm/gma500/framebuffer.c
> > > +++ b/drivers/gpu/drm/gma500/framebuffer.c
> > > @@ -462,6 +462,7 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> > >                 container_of(helper, struct psb_fbdev, psb_fb_helper);
> > >         struct drm_device *dev = psb_fbdev->psb_fb_helper.dev;
> > >         struct drm_psb_private *dev_priv = dev->dev_private;
> > > +       unsigned int fb_size;
> > >         int bytespp;
> > >
> > >         bytespp = sizes->surface_bpp / 8;
> > > @@ -471,8 +472,11 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> > >         /* If the mode will not fit in 32bit then switch to 16bit to get
> > >            a console on full resolution. The X mode setting server will
> > >            allocate its own 32bit GEM framebuffer */
> > > -       if (ALIGN(sizes->fb_width * bytespp, 64) * sizes->fb_height >
> > > -                       dev_priv->vram_stolen_size) {
> > > +       fb_size = ALIGN(sizes->surface_width * bytespp, 64) *
> > > +                 sizes->surface_height;
> > > +       fb_size = ALIGN(fb_size, PAGE_SIZE);
> > > +
> > > +       if (fb_size > dev_priv->vram_stolen_size) {
> > 
> > psb_gtt_alloc_range() already aligns by PAGE_SIZE for us. Looks like
> > we align a couple of times extra for luck. This needs cleaning up
> > instead of adding even more aligns.
> 
> I'm not sure this is really for luck. As far as I can see, we need to do it
> properly for this size estimation since it's the final size that will be
> allocated (and thus needs to be available in whole).
> 
> For the other times there is explicit alignment, they seem justified too:
> - in psb_gem_create: it is common to pass the aligned size when creating the
>   associated GEM object with drm_gem_object_init, even though it's probably not
>   crucial given that this is not where allocation actually happens;
> - in psbfb_create: the full size is apparently only really used to memset 0
>   the allocated buffer. I think this makes sense for security reasons (and not
>   leak previous contents in the additional space required for alignment).
> 
> What strikes me however is that each call to psb_gtt_alloc_range takes the
> alignment as a parameter when it's really always PAGE_SIZE, so it should
> probably just be hardcoded in the call to allocate_resource.
> 
> What do you think?
> 
> > Your size calculation looks correct and indeed makes my 1024x600 +
> > 1920x1080 setup actually display something, but for some reason I get
> > an incorrect panning on the smaller screen and stale data on the
> > surface only visible by the larger CRTC. Any idea what's going on?
> 
> I'm not seeing this immediately, but I definitely have something strange
> after having printed more lines than the smallest display can handle or
> scrolling, where more than the actual size of the fb is used.
> 
> Maybe this is related to using the PowerVR-accelerated fb ops, that aren't
> quite ready for this use case?
> 
> I'll give it a try with psbfb_roll_ops and psbfb_unaccel_ops instead to see
> if it changes something for me. Maybe it would help for you too?

Some quick feedback about that:
- psbfb_unaccel_ops gives a correct result where the scrolling area is bound
  to the smallest display;
- psbfb_roll_ops gives a working scrolling but bound to the largest display
  (so the current shell line becomes invisible on the smallest one eventually);
- psbfb_ops gives the same issue as above and seems to add artifacts on top.

There's probably limited interest in working on that aspect on our side though.
I'd be interested to know if it affects the issue you're seeing though.

Cheers,

Paul

> I suspect that the generic implementation is already bullet-proof for these
> kinds of use case.
> 
> Cheers and thanks for the feedback,
> 
> Paul
> 
> > 
> > >                  sizes->surface_bpp = 16;
> > >                  sizes->surface_depth = 16;
> > >          }
> > > --
> > > 2.23.0
> > >
> 
> -- 
> Paul Kocialkowski, Bootlin
> Embedded Linux and kernel engineering
> https://bootlin.com
Patrik Jakobsson Nov. 13, 2019, 10:04 a.m. UTC | #4
On Tue, Nov 12, 2019 at 4:50 PM Paul Kocialkowski
<paul.kocialkowski@bootlin.com> wrote:
>
> Hi,
>
> On Tue 12 Nov 19, 16:11, Paul Kocialkowski wrote:
> > Hi,
> >
> > On Tue 12 Nov 19, 11:20, Patrik Jakobsson wrote:
> > > On Thu, Nov 7, 2019 at 4:30 PM Paul Kocialkowski
> > > <paul.kocialkowski@bootlin.com> wrote:
> > > >
> > > > psbfb_probe performs an evaluation of the required size from the stolen
> > > > GTT memory, but gets it wrong in two distinct ways:
> > > > - The resulting size must be page-size-aligned;
> > > > - The size to allocate is derived from the surface dimensions, not the fb
> > > >   dimensions.
> > > >
> > > > When two connectors are connected with different modes, the smallest will
> > > > be stored in the fb dimensions, but the size that needs to be allocated must
> > > > match the largest (surface) dimensions. This is what is used in the actual
> > > > allocation code.
> > > >
> > > > Fix this by correcting the evaluation to conform to the two points above.
> > > > It allows correctly switching to 16bpp when one connector is e.g. 1920x1080
> > > > and the other is 1024x768.
> > > >
> > > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> > > > ---
> > > >  drivers/gpu/drm/gma500/framebuffer.c | 8 ++++++--
> > > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c
> > > > index 218f3bb15276..90237abee088 100644
> > > > --- a/drivers/gpu/drm/gma500/framebuffer.c
> > > > +++ b/drivers/gpu/drm/gma500/framebuffer.c
> > > > @@ -462,6 +462,7 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> > > >                 container_of(helper, struct psb_fbdev, psb_fb_helper);
> > > >         struct drm_device *dev = psb_fbdev->psb_fb_helper.dev;
> > > >         struct drm_psb_private *dev_priv = dev->dev_private;
> > > > +       unsigned int fb_size;
> > > >         int bytespp;
> > > >
> > > >         bytespp = sizes->surface_bpp / 8;
> > > > @@ -471,8 +472,11 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> > > >         /* If the mode will not fit in 32bit then switch to 16bit to get
> > > >            a console on full resolution. The X mode setting server will
> > > >            allocate its own 32bit GEM framebuffer */
> > > > -       if (ALIGN(sizes->fb_width * bytespp, 64) * sizes->fb_height >
> > > > -                       dev_priv->vram_stolen_size) {
> > > > +       fb_size = ALIGN(sizes->surface_width * bytespp, 64) *
> > > > +                 sizes->surface_height;
> > > > +       fb_size = ALIGN(fb_size, PAGE_SIZE);
> > > > +
> > > > +       if (fb_size > dev_priv->vram_stolen_size) {
> > >
> > > psb_gtt_alloc_range() already aligns by PAGE_SIZE for us. Looks like
> > > we align a couple of times extra for luck. This needs cleaning up
> > > instead of adding even more aligns.
> >
> > I'm not sure this is really for luck. As far as I can see, we need to do it
> > properly for this size estimation since it's the final size that will be
> > allocated (and thus needs to be available in whole).

Ok now I understand what you meant. Actually vram_stolen_size is
always page aligned so fb_size doesn't need any page alignment here.
There is also no need to align for psbfb_create() since it also takes
care of this.

> >
> > For the other times there is explicit alignment, they seem justified too:
> > - in psb_gem_create: it is common to pass the aligned size when creating the
> >   associated GEM object with drm_gem_object_init, even though it's probably not
> >   crucial given that this is not where allocation actually happens;
> > - in psbfb_create: the full size is apparently only really used to memset 0
> >   the allocated buffer. I think this makes sense for security reasons (and not
> >   leak previous contents in the additional space required for alignment).

What I would prefer is to have a single place where the alignment is
made so any hardware requirements would be transparent to the rest of
the code.

Best would be if alignment is only made in psb_gtt_alloc_range() and
then store the actual size in struct gtt_range. That way we can just
pass along that value to memset() and drm_gem_object_init() without
caring about how it is adjusted.

> >
> > What strikes me however is that each call to psb_gtt_alloc_range takes the
> > alignment as a parameter when it's really always PAGE_SIZE, so it should
> > probably just be hardcoded in the call to allocate_resource.

This is a remnant from trying to add support for 2D and/or overlay
planes (don't really remember). Doesn't matter if it stays or goes
away.

> >
> > What do you think?

I suppose most of this is outside the scope of what you're trying to
do so we can just leave it as is and I can clean it up later.

> >
> > > Your size calculation looks correct and indeed makes my 1024x600 +
> > > 1920x1080 setup actually display something, but for some reason I get
> > > an incorrect panning on the smaller screen and stale data on the
> > > surface only visible by the larger CRTC. Any idea what's going on?
> >
> > I'm not seeing this immediately, but I definitely have something strange
> > after having printed more lines than the smallest display can handle or
> > scrolling, where more than the actual size of the fb is used.
> >
> > Maybe this is related to using the PowerVR-accelerated fb ops, that aren't
> > quite ready for this use case?
> >
> > I'll give it a try with psbfb_roll_ops and psbfb_unaccel_ops instead to see
> > if it changes something for me. Maybe it would help for you too?
>
> Some quick feedback about that:
> - psbfb_unaccel_ops gives a correct result where the scrolling area is bound
>   to the smallest display;

Yes, this also works correctly for me.

> - psbfb_roll_ops gives a working scrolling but bound to the largest display
>   (so the current shell line becomes invisible on the smallest one eventually);

It's not panning at all for me. I never really found gtt rolling to be
useful. It's a neat trick but I didn't have a problem with console
scrolling speed to begin with. I might just remove it.

> - psbfb_ops gives the same issue as above and seems to add artifacts on top.

Did you try this on CDV? There's only 2D acceleration on Poulsbo and Oaktrail.

>
> There's probably limited interest in working on that aspect on our side though.
> I'd be interested to know if it affects the issue you're seeing though.

Focus on your requirements and I'll look at the rest.

-Patrik

>
> Cheers,
>
> Paul
>
> > I suspect that the generic implementation is already bullet-proof for these
> > kinds of use case.
> >
> > Cheers and thanks for the feedback,
> >
> > Paul
> >
> > >
> > > >                  sizes->surface_bpp = 16;
> > > >                  sizes->surface_depth = 16;
> > > >          }
> > > > --
> > > > 2.23.0
> > > >
> >
> > --
> > Paul Kocialkowski, Bootlin
> > Embedded Linux and kernel engineering
> > https://bootlin.com
>
>
>
> --
> Paul Kocialkowski, Bootlin
> Embedded Linux and kernel engineering
> https://bootlin.com
Paul Kocialkowski Nov. 19, 2019, 2:11 p.m. UTC | #5
Hi,

On Wed 13 Nov 19, 11:04, Patrik Jakobsson wrote:
> On Tue, Nov 12, 2019 at 4:50 PM Paul Kocialkowski
> <paul.kocialkowski@bootlin.com> wrote:
> >
> > Hi,
> >
> > On Tue 12 Nov 19, 16:11, Paul Kocialkowski wrote:
> > > Hi,
> > >
> > > On Tue 12 Nov 19, 11:20, Patrik Jakobsson wrote:
> > > > On Thu, Nov 7, 2019 at 4:30 PM Paul Kocialkowski
> > > > <paul.kocialkowski@bootlin.com> wrote:
> > > > >
> > > > > psbfb_probe performs an evaluation of the required size from the stolen
> > > > > GTT memory, but gets it wrong in two distinct ways:
> > > > > - The resulting size must be page-size-aligned;
> > > > > - The size to allocate is derived from the surface dimensions, not the fb
> > > > >   dimensions.
> > > > >
> > > > > When two connectors are connected with different modes, the smallest will
> > > > > be stored in the fb dimensions, but the size that needs to be allocated must
> > > > > match the largest (surface) dimensions. This is what is used in the actual
> > > > > allocation code.
> > > > >
> > > > > Fix this by correcting the evaluation to conform to the two points above.
> > > > > It allows correctly switching to 16bpp when one connector is e.g. 1920x1080
> > > > > and the other is 1024x768.
> > > > >
> > > > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> > > > > ---
> > > > >  drivers/gpu/drm/gma500/framebuffer.c | 8 ++++++--
> > > > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c
> > > > > index 218f3bb15276..90237abee088 100644
> > > > > --- a/drivers/gpu/drm/gma500/framebuffer.c
> > > > > +++ b/drivers/gpu/drm/gma500/framebuffer.c
> > > > > @@ -462,6 +462,7 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> > > > >                 container_of(helper, struct psb_fbdev, psb_fb_helper);
> > > > >         struct drm_device *dev = psb_fbdev->psb_fb_helper.dev;
> > > > >         struct drm_psb_private *dev_priv = dev->dev_private;
> > > > > +       unsigned int fb_size;
> > > > >         int bytespp;
> > > > >
> > > > >         bytespp = sizes->surface_bpp / 8;
> > > > > @@ -471,8 +472,11 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> > > > >         /* If the mode will not fit in 32bit then switch to 16bit to get
> > > > >            a console on full resolution. The X mode setting server will
> > > > >            allocate its own 32bit GEM framebuffer */
> > > > > -       if (ALIGN(sizes->fb_width * bytespp, 64) * sizes->fb_height >
> > > > > -                       dev_priv->vram_stolen_size) {
> > > > > +       fb_size = ALIGN(sizes->surface_width * bytespp, 64) *
> > > > > +                 sizes->surface_height;
> > > > > +       fb_size = ALIGN(fb_size, PAGE_SIZE);
> > > > > +
> > > > > +       if (fb_size > dev_priv->vram_stolen_size) {
> > > >
> > > > psb_gtt_alloc_range() already aligns by PAGE_SIZE for us. Looks like
> > > > we align a couple of times extra for luck. This needs cleaning up
> > > > instead of adding even more aligns.
> > >
> > > I'm not sure this is really for luck. As far as I can see, we need to do it
> > > properly for this size estimation since it's the final size that will be
> > > allocated (and thus needs to be available in whole).
> 
> Ok now I understand what you meant. Actually vram_stolen_size is
> always page aligned so fb_size doesn't need any page alignment here.

I'm a bit confused here, what about the case where:
unaligned fb_size < dev_priv->vram_stolen_size but
aligned fb_size > dev_priv->vram_stolen_size ?

Granted, it's a corner case, but I don't follow the logic of comparing aligned
and unaligned sizes: it feels a bit like comparing two values of different
units.

> There is also no need to align for psbfb_create() since it also takes
> care of this.
> 
> > >
> > > For the other times there is explicit alignment, they seem justified too:
> > > - in psb_gem_create: it is common to pass the aligned size when creating the
> > >   associated GEM object with drm_gem_object_init, even though it's probably not
> > >   crucial given that this is not where allocation actually happens;
> > > - in psbfb_create: the full size is apparently only really used to memset 0
> > >   the allocated buffer. I think this makes sense for security reasons (and not
> > >   leak previous contents in the additional space required for alignment).
> 
> What I would prefer is to have a single place where the alignment is
> made so any hardware requirements would be transparent to the rest of
> the code.

Mhh, I thought that psbfb_create needs to be aware of the alignment in the
form of the pitch_lines variable to decide which 2d accel method can be used or
not (depending on associated alignment requirements). I guess this makes for
another reason to ditch the accelerated 2d accel support.

> Best would be if alignment is only made in psb_gtt_alloc_range() and
> then store the actual size in struct gtt_range. That way we can just
> pass along that value to memset() and drm_gem_object_init() without
> caring about how it is adjusted.
> 
> > >
> > > What strikes me however is that each call to psb_gtt_alloc_range takes the
> > > alignment as a parameter when it's really always PAGE_SIZE, so it should
> > > probably just be hardcoded in the call to allocate_resource.
> 
> This is a remnant from trying to add support for 2D and/or overlay
> planes (don't really remember). Doesn't matter if it stays or goes
> away.
> 
> > >
> > > What do you think?
> 
> I suppose most of this is outside the scope of what you're trying to
> do so we can just leave it as is and I can clean it up later.

I guess my main change here was to switch from sizes->fb_width/height to
sizes->surface_width/height anyway, yes. I can totally live without the
final PAGE_SIZE align for fb_size too (even though I think it makes sense).

Feel free to let me know what you'd like to receive as a v2 here and I'll do
that :)

> > >
> > > > Your size calculation looks correct and indeed makes my 1024x600 +
> > > > 1920x1080 setup actually display something, but for some reason I get
> > > > an incorrect panning on the smaller screen and stale data on the
> > > > surface only visible by the larger CRTC. Any idea what's going on?
> > >
> > > I'm not seeing this immediately, but I definitely have something strange
> > > after having printed more lines than the smallest display can handle or
> > > scrolling, where more than the actual size of the fb is used.
> > >
> > > Maybe this is related to using the PowerVR-accelerated fb ops, that aren't
> > > quite ready for this use case?
> > >
> > > I'll give it a try with psbfb_roll_ops and psbfb_unaccel_ops instead to see
> > > if it changes something for me. Maybe it would help for you too?
> >
> > Some quick feedback about that:
> > - psbfb_unaccel_ops gives a correct result where the scrolling area is bound
> >   to the smallest display;
> 
> Yes, this also works correctly for me.
> 
> > - psbfb_roll_ops gives a working scrolling but bound to the largest display
> >   (so the current shell line becomes invisible on the smallest one eventually);
> 
> It's not panning at all for me. I never really found gtt rolling to be
> useful. It's a neat trick but I didn't have a problem with console
> scrolling speed to begin with. I might just remove it.

Yeah, I also don't understand what the hype of accelerating fbdev ops is about.
I guess it could have been useful back when there were serious users of fbdev in
userspace (aka directfb) but that's not really where things are going today.
For console usage, I also find the software method fast enough.

> > - psbfb_ops gives the same issue as above and seems to add artifacts on top.
> 
> Did you try this on CDV? There's only 2D acceleration on Poulsbo and Oaktrail.

I tried this one on Poulsbo (the other gma500 platform I have around).

> >
> > There's probably limited interest in working on that aspect on our side though.
> > I'd be interested to know if it affects the issue you're seeing though.
> 
> Focus on your requirements and I'll look at the rest.

Sounds good to me, thanks a lot! I'll do according to what you'd like for a v2.

Cheers,

Paul

> -Patrik
> 
> >
> > Cheers,
> >
> > Paul
> >
> > > I suspect that the generic implementation is already bullet-proof for these
> > > kinds of use case.
> > >
> > > Cheers and thanks for the feedback,
> > >
> > > Paul
> > >
> > > >
> > > > >                  sizes->surface_bpp = 16;
> > > > >                  sizes->surface_depth = 16;
> > > > >          }
> > > > > --
> > > > > 2.23.0
> > > > >
> > >
> > > --
> > > Paul Kocialkowski, Bootlin
> > > Embedded Linux and kernel engineering
> > > https://bootlin.com
> >
> >
> >
> > --
> > Paul Kocialkowski, Bootlin
> > Embedded Linux and kernel engineering
> > https://bootlin.com
Patrik Jakobsson Nov. 19, 2019, 8:46 p.m. UTC | #6
On Tue, Nov 19, 2019 at 3:11 PM Paul Kocialkowski
<paul.kocialkowski@bootlin.com> wrote:
>
> Hi,
>
> On Wed 13 Nov 19, 11:04, Patrik Jakobsson wrote:
> > On Tue, Nov 12, 2019 at 4:50 PM Paul Kocialkowski
> > <paul.kocialkowski@bootlin.com> wrote:
> > >
> > > Hi,
> > >
> > > On Tue 12 Nov 19, 16:11, Paul Kocialkowski wrote:
> > > > Hi,
> > > >
> > > > On Tue 12 Nov 19, 11:20, Patrik Jakobsson wrote:
> > > > > On Thu, Nov 7, 2019 at 4:30 PM Paul Kocialkowski
> > > > > <paul.kocialkowski@bootlin.com> wrote:
> > > > > >
> > > > > > psbfb_probe performs an evaluation of the required size from the stolen
> > > > > > GTT memory, but gets it wrong in two distinct ways:
> > > > > > - The resulting size must be page-size-aligned;
> > > > > > - The size to allocate is derived from the surface dimensions, not the fb
> > > > > >   dimensions.
> > > > > >
> > > > > > When two connectors are connected with different modes, the smallest will
> > > > > > be stored in the fb dimensions, but the size that needs to be allocated must
> > > > > > match the largest (surface) dimensions. This is what is used in the actual
> > > > > > allocation code.
> > > > > >
> > > > > > Fix this by correcting the evaluation to conform to the two points above.
> > > > > > It allows correctly switching to 16bpp when one connector is e.g. 1920x1080
> > > > > > and the other is 1024x768.
> > > > > >
> > > > > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> > > > > > ---
> > > > > >  drivers/gpu/drm/gma500/framebuffer.c | 8 ++++++--
> > > > > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c
> > > > > > index 218f3bb15276..90237abee088 100644
> > > > > > --- a/drivers/gpu/drm/gma500/framebuffer.c
> > > > > > +++ b/drivers/gpu/drm/gma500/framebuffer.c
> > > > > > @@ -462,6 +462,7 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> > > > > >                 container_of(helper, struct psb_fbdev, psb_fb_helper);
> > > > > >         struct drm_device *dev = psb_fbdev->psb_fb_helper.dev;
> > > > > >         struct drm_psb_private *dev_priv = dev->dev_private;
> > > > > > +       unsigned int fb_size;
> > > > > >         int bytespp;
> > > > > >
> > > > > >         bytespp = sizes->surface_bpp / 8;
> > > > > > @@ -471,8 +472,11 @@ static int psbfb_probe(struct drm_fb_helper *helper,
> > > > > >         /* If the mode will not fit in 32bit then switch to 16bit to get
> > > > > >            a console on full resolution. The X mode setting server will
> > > > > >            allocate its own 32bit GEM framebuffer */
> > > > > > -       if (ALIGN(sizes->fb_width * bytespp, 64) * sizes->fb_height >
> > > > > > -                       dev_priv->vram_stolen_size) {
> > > > > > +       fb_size = ALIGN(sizes->surface_width * bytespp, 64) *
> > > > > > +                 sizes->surface_height;
> > > > > > +       fb_size = ALIGN(fb_size, PAGE_SIZE);
> > > > > > +
> > > > > > +       if (fb_size > dev_priv->vram_stolen_size) {
> > > > >
> > > > > psb_gtt_alloc_range() already aligns by PAGE_SIZE for us. Looks like
> > > > > we align a couple of times extra for luck. This needs cleaning up
> > > > > instead of adding even more aligns.
> > > >
> > > > I'm not sure this is really for luck. As far as I can see, we need to do it
> > > > properly for this size estimation since it's the final size that will be
> > > > allocated (and thus needs to be available in whole).
> >
> > Ok now I understand what you meant. Actually vram_stolen_size is
> > always page aligned so fb_size doesn't need any page alignment here.
>
> I'm a bit confused here, what about the case where:
> unaligned fb_size < dev_priv->vram_stolen_size but
> aligned fb_size > dev_priv->vram_stolen_size ?

That can never happen since aligning fb_size will never cross a page
boundary, and stolen_size is always on a page boundary. Not sure how
to explain it on a good way but:
If stolen_size = 4096, then fb_size is only more than stolen_size if
it is actually > 4096 regardless if we align it or not.

>
> Granted, it's a corner case, but I don't follow the logic of comparing aligned
> and unaligned sizes: it feels a bit like comparing two values of different
> units.

We can keep it if you think it makes the code more readable.

>
> > There is also no need to align for psbfb_create() since it also takes
> > care of this.
> >
> > > >
> > > > For the other times there is explicit alignment, they seem justified too:
> > > > - in psb_gem_create: it is common to pass the aligned size when creating the
> > > >   associated GEM object with drm_gem_object_init, even though it's probably not
> > > >   crucial given that this is not where allocation actually happens;
> > > > - in psbfb_create: the full size is apparently only really used to memset 0
> > > >   the allocated buffer. I think this makes sense for security reasons (and not
> > > >   leak previous contents in the additional space required for alignment).
> >
> > What I would prefer is to have a single place where the alignment is
> > made so any hardware requirements would be transparent to the rest of
> > the code.
>
> Mhh, I thought that psbfb_create needs to be aware of the alignment in the
> form of the pitch_lines variable to decide which 2d accel method can be used or
> not (depending on associated alignment requirements). I guess this makes for
> another reason to ditch the accelerated 2d accel support.

I was only thinking of the size alignment. Yes, ditching 2D would make
life easier in this regard.

>
> > Best would be if alignment is only made in psb_gtt_alloc_range() and
> > then store the actual size in struct gtt_range. That way we can just
> > pass along that value to memset() and drm_gem_object_init() without
> > caring about how it is adjusted.
> >
> > > >
> > > > What strikes me however is that each call to psb_gtt_alloc_range takes the
> > > > alignment as a parameter when it's really always PAGE_SIZE, so it should
> > > > probably just be hardcoded in the call to allocate_resource.
> >
> > This is a remnant from trying to add support for 2D and/or overlay
> > planes (don't really remember). Doesn't matter if it stays or goes
> > away.
> >
> > > >
> > > > What do you think?
> >
> > I suppose most of this is outside the scope of what you're trying to
> > do so we can just leave it as is and I can clean it up later.
>
> I guess my main change here was to switch from sizes->fb_width/height to
> sizes->surface_width/height anyway, yes. I can totally live without the
> final PAGE_SIZE align for fb_size too (even though I think it makes sense).
>
> Feel free to let me know what you'd like to receive as a v2 here and I'll do
> that :)

Let's keep it as it is with the motivation that it increases readability.

Applied to drm-misc-next.
Thanks

>
> > > >
> > > > > Your size calculation looks correct and indeed makes my 1024x600 +
> > > > > 1920x1080 setup actually display something, but for some reason I get
> > > > > an incorrect panning on the smaller screen and stale data on the
> > > > > surface only visible by the larger CRTC. Any idea what's going on?
> > > >
> > > > I'm not seeing this immediately, but I definitely have something strange
> > > > after having printed more lines than the smallest display can handle or
> > > > scrolling, where more than the actual size of the fb is used.
> > > >
> > > > Maybe this is related to using the PowerVR-accelerated fb ops, that aren't
> > > > quite ready for this use case?
> > > >
> > > > I'll give it a try with psbfb_roll_ops and psbfb_unaccel_ops instead to see
> > > > if it changes something for me. Maybe it would help for you too?
> > >
> > > Some quick feedback about that:
> > > - psbfb_unaccel_ops gives a correct result where the scrolling area is bound
> > >   to the smallest display;
> >
> > Yes, this also works correctly for me.
> >
> > > - psbfb_roll_ops gives a working scrolling but bound to the largest display
> > >   (so the current shell line becomes invisible on the smallest one eventually);
> >
> > It's not panning at all for me. I never really found gtt rolling to be
> > useful. It's a neat trick but I didn't have a problem with console
> > scrolling speed to begin with. I might just remove it.
>
> Yeah, I also don't understand what the hype of accelerating fbdev ops is about.
> I guess it could have been useful back when there were serious users of fbdev in
> userspace (aka directfb) but that's not really where things are going today.
> For console usage, I also find the software method fast enough.
>
> > > - psbfb_ops gives the same issue as above and seems to add artifacts on top.
> >
> > Did you try this on CDV? There's only 2D acceleration on Poulsbo and Oaktrail.
>
> I tried this one on Poulsbo (the other gma500 platform I have around).
>
> > >
> > > There's probably limited interest in working on that aspect on our side though.
> > > I'd be interested to know if it affects the issue you're seeing though.
> >
> > Focus on your requirements and I'll look at the rest.
>
> Sounds good to me, thanks a lot! I'll do according to what you'd like for a v2.
>
> Cheers,
>
> Paul
>
> > -Patrik
> >
> > >
> > > Cheers,
> > >
> > > Paul
> > >
> > > > I suspect that the generic implementation is already bullet-proof for these
> > > > kinds of use case.
> > > >
> > > > Cheers and thanks for the feedback,
> > > >
> > > > Paul
> > > >
> > > > >
> > > > > >                  sizes->surface_bpp = 16;
> > > > > >                  sizes->surface_depth = 16;
> > > > > >          }
> > > > > > --
> > > > > > 2.23.0
> > > > > >
> > > >
> > > > --
> > > > Paul Kocialkowski, Bootlin
> > > > Embedded Linux and kernel engineering
> > > > https://bootlin.com
> > >
> > >
> > >
> > > --
> > > Paul Kocialkowski, Bootlin
> > > Embedded Linux and kernel engineering
> > > https://bootlin.com
>
> --
> Paul Kocialkowski, Bootlin
> Embedded Linux and kernel engineering
> https://bootlin.com

Patch
diff mbox series

diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c
index 218f3bb15276..90237abee088 100644
--- a/drivers/gpu/drm/gma500/framebuffer.c
+++ b/drivers/gpu/drm/gma500/framebuffer.c
@@ -462,6 +462,7 @@  static int psbfb_probe(struct drm_fb_helper *helper,
 		container_of(helper, struct psb_fbdev, psb_fb_helper);
 	struct drm_device *dev = psb_fbdev->psb_fb_helper.dev;
 	struct drm_psb_private *dev_priv = dev->dev_private;
+	unsigned int fb_size;
 	int bytespp;
 
 	bytespp = sizes->surface_bpp / 8;
@@ -471,8 +472,11 @@  static int psbfb_probe(struct drm_fb_helper *helper,
 	/* If the mode will not fit in 32bit then switch to 16bit to get
 	   a console on full resolution. The X mode setting server will
 	   allocate its own 32bit GEM framebuffer */
-	if (ALIGN(sizes->fb_width * bytespp, 64) * sizes->fb_height >
-	                dev_priv->vram_stolen_size) {
+	fb_size = ALIGN(sizes->surface_width * bytespp, 64) *
+		  sizes->surface_height;
+	fb_size = ALIGN(fb_size, PAGE_SIZE);
+
+	if (fb_size > dev_priv->vram_stolen_size) {
                 sizes->surface_bpp = 16;
                 sizes->surface_depth = 16;
         }