[PATCH] drm: rcar-du: track dma-buf fences

[PATCH] drm: rcar-du: track dma-buf fences

[Emre Ucan]

We have to check dma-buf reservation objects
of our framebuffers before we use them.
Otherwise, another driver might be writing
on the same buffer which we are using.
This would cause visible tearing effects
on display.

We can use existing atomic helper functions
to solve this problem.

Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
---
 drivers/gpu/drm/rcar-du/rcar_du_kms.c |  2 ++
 drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
index 0329b35..f3da3d1 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
@@ -255,6 +255,8 @@ static void rcar_du_atomic_commit_tail(struct drm_atomic_state *old_state)
 {
 	struct drm_device *dev = old_state->dev;
 
+	drm_atomic_helper_wait_for_fences(dev, old_state, false);
+
 	/* Apply the atomic update. */
 	drm_atomic_helper_commit_modeset_disables(dev, old_state);
 	drm_atomic_helper_commit_planes(dev, old_state,
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
index 2c260c3..482e23c 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
@@ -18,12 +18,16 @@
 #include <drm/drm_fb_cma_helper.h>
 #include <drm/drm_gem_cma_helper.h>
 #include <drm/drm_plane_helper.h>
+#include <drm/drm_atomic.h>
 
 #include <linux/bitops.h>
 #include <linux/dma-mapping.h>
+#include <linux/dma-fence.h>
+#include <linux/dma-buf.h>
 #include <linux/of_platform.h>
 #include <linux/scatterlist.h>
 #include <linux/videodev2.h>
+#include <linux/reservation.h>
 
 #include <media/vsp1.h>
 
@@ -203,6 +207,20 @@ static void rcar_du_vsp_plane_setup(struct rcar_du_vsp_plane *plane)
 			      plane->index, &cfg);
 }
 
+static void rcar_du_vsp_set_fence_for_plane(struct drm_plane_state *state)
+{
+	struct drm_gem_cma_object *gem;
+	struct dma_buf *dma_buf;
+	struct dma_fence *fence;
+
+	gem = drm_fb_cma_get_gem_obj(state->fb, 0);
+	dma_buf = gem->base.dma_buf;
+	if (dma_buf) {
+		fence = reservation_object_get_excl_rcu(dma_buf->resv);
+		drm_atomic_set_fence_for_plane(state, fence);
+	}
+}
+
 static int rcar_du_vsp_plane_prepare_fb(struct drm_plane *plane,
 					struct drm_plane_state *state)
 {
@@ -237,6 +255,8 @@ static int rcar_du_vsp_plane_prepare_fb(struct drm_plane *plane,
 		}
 	}
 
+	rcar_du_vsp_set_fence_for_plane(state);
+
 	return 0;
 
 fail:
-- 
2.7.4

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH] drm: rcar-du: track dma-buf fences

[Laurent Pinchart]

Hello Emre,

Thank you for the patch.

On Tuesday, 3 April 2018 12:14:33 EEST Emre Ucan wrote:
> We have to check dma-buf reservation objects
> of our framebuffers before we use them.
> Otherwise, another driver might be writing
> on the same buffer which we are using.
> This would cause visible tearing effects
> on display.
> 
> We can use existing atomic helper functions
> to solve this problem.
> 
> Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
> ---
>  drivers/gpu/drm/rcar-du/rcar_du_kms.c |  2 ++
>  drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 20 ++++++++++++++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> b/drivers/gpu/drm/rcar-du/rcar_du_kms.c index 0329b35..f3da3d1 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> @@ -255,6 +255,8 @@ static void rcar_du_atomic_commit_tail(struct
> drm_atomic_state *old_state) {
>  	struct drm_device *dev = old_state->dev;
> 
> +	drm_atomic_helper_wait_for_fences(dev, old_state, false);
> +

The commit_tail() function in drm_atomic_helper.c, which calls our 
atomic_commit_tail() implementation, already calls 
drm_atomic_helper_wait_for_fences(). Why is there a need to duplicate the call 
here ?

>  	/* Apply the atomic update. */
>  	drm_atomic_helper_commit_modeset_disables(dev, old_state);
>  	drm_atomic_helper_commit_planes(dev, old_state,
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c index 2c260c3..482e23c 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> @@ -18,12 +18,16 @@
>  #include <drm/drm_fb_cma_helper.h>
>  #include <drm/drm_gem_cma_helper.h>
>  #include <drm/drm_plane_helper.h>
> +#include <drm/drm_atomic.h>
> 
>  #include <linux/bitops.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/dma-fence.h>
> +#include <linux/dma-buf.h>
>  #include <linux/of_platform.h>
>  #include <linux/scatterlist.h>
>  #include <linux/videodev2.h>
> +#include <linux/reservation.h>
> 
>  #include <media/vsp1.h>
> 
> @@ -203,6 +207,20 @@ static void rcar_du_vsp_plane_setup(struct
> rcar_du_vsp_plane *plane) plane->index, &cfg);
>  }
> 
> +static void rcar_du_vsp_set_fence_for_plane(struct drm_plane_state *state)
> +{
> +	struct drm_gem_cma_object *gem;
> +	struct dma_buf *dma_buf;
> +	struct dma_fence *fence;
> +
> +	gem = drm_fb_cma_get_gem_obj(state->fb, 0);
> +	dma_buf = gem->base.dma_buf;
> +	if (dma_buf) {
> +		fence = reservation_object_get_excl_rcu(dma_buf->resv);
> +		drm_atomic_set_fence_for_plane(state, fence);

Unless I'm mistaken this is used for implicit fencing only. What is your use 
case, wouldn't it be better for userspace to use explicit fencing as that is 
the fence model that has been selected for display ?

> +	}
> +}

This looks very similar to drm_gem_fb_prepare_fb(), couldn't you use that 
function instead ?

>  static int rcar_du_vsp_plane_prepare_fb(struct drm_plane *plane,
>  					struct drm_plane_state *state)
>  {
> @@ -237,6 +255,8 @@ static int rcar_du_vsp_plane_prepare_fb(struct drm_plane
> *plane, }
>  	}
> 
> +	rcar_du_vsp_set_fence_for_plane(state);
> +
>  	return 0;
> 
>  fail:

-- 
Regards,

Laurent Pinchart



_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH] drm: rcar-du: track dma-buf fences

[Daniel Vetter]

On Tue, Apr 3, 2018 at 8:53 PM, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> Hello Emre,
>
> Thank you for the patch.
>
> On Tuesday, 3 April 2018 12:14:33 EEST Emre Ucan wrote:
>> We have to check dma-buf reservation objects
>> of our framebuffers before we use them.
>> Otherwise, another driver might be writing
>> on the same buffer which we are using.
>> This would cause visible tearing effects
>> on display.
>>
>> We can use existing atomic helper functions
>> to solve this problem.
>>
>> Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
>> ---
>>  drivers/gpu/drm/rcar-du/rcar_du_kms.c |  2 ++
>>  drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 20 ++++++++++++++++++++
>>  2 files changed, 22 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> b/drivers/gpu/drm/rcar-du/rcar_du_kms.c index 0329b35..f3da3d1 100644
>> --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> @@ -255,6 +255,8 @@ static void rcar_du_atomic_commit_tail(struct
>> drm_atomic_state *old_state) {
>>       struct drm_device *dev = old_state->dev;
>>
>> +     drm_atomic_helper_wait_for_fences(dev, old_state, false);
>> +
>
> The commit_tail() function in drm_atomic_helper.c, which calls our
> atomic_commit_tail() implementation, already calls
> drm_atomic_helper_wait_for_fences(). Why is there a need to duplicate the call
> here ?
>
>>       /* Apply the atomic update. */
>>       drm_atomic_helper_commit_modeset_disables(dev, old_state);
>>       drm_atomic_helper_commit_planes(dev, old_state,
>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
>> b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c index 2c260c3..482e23c 100644
>> --- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
>> @@ -18,12 +18,16 @@
>>  #include <drm/drm_fb_cma_helper.h>
>>  #include <drm/drm_gem_cma_helper.h>
>>  #include <drm/drm_plane_helper.h>
>> +#include <drm/drm_atomic.h>
>>
>>  #include <linux/bitops.h>
>>  #include <linux/dma-mapping.h>
>> +#include <linux/dma-fence.h>
>> +#include <linux/dma-buf.h>
>>  #include <linux/of_platform.h>
>>  #include <linux/scatterlist.h>
>>  #include <linux/videodev2.h>
>> +#include <linux/reservation.h>
>>
>>  #include <media/vsp1.h>
>>
>> @@ -203,6 +207,20 @@ static void rcar_du_vsp_plane_setup(struct
>> rcar_du_vsp_plane *plane) plane->index, &cfg);
>>  }
>>
>> +static void rcar_du_vsp_set_fence_for_plane(struct drm_plane_state *state)
>> +{
>> +     struct drm_gem_cma_object *gem;
>> +     struct dma_buf *dma_buf;
>> +     struct dma_fence *fence;
>> +
>> +     gem = drm_fb_cma_get_gem_obj(state->fb, 0);
>> +     dma_buf = gem->base.dma_buf;
>> +     if (dma_buf) {
>> +             fence = reservation_object_get_excl_rcu(dma_buf->resv);
>> +             drm_atomic_set_fence_for_plane(state, fence);
>
> Unless I'm mistaken this is used for implicit fencing only. What is your use
> case, wouldn't it be better for userspace to use explicit fencing as that is
> the fence model that has been selected for display ?

Implicit fencing is very much still a thing on most X and wayland
setups. There's a push to eventually make everything explicit, but
it'll take a while I think.
-Daniel

>
>> +     }
>> +}
>
> This looks very similar to drm_gem_fb_prepare_fb(), couldn't you use that
> function instead ?
>
>>  static int rcar_du_vsp_plane_prepare_fb(struct drm_plane *plane,
>>                                       struct drm_plane_state *state)
>>  {
>> @@ -237,6 +255,8 @@ static int rcar_du_vsp_plane_prepare_fb(struct drm_plane
>> *plane, }
>>       }
>>
>> +     rcar_du_vsp_set_fence_for_plane(state);
>> +
>>       return 0;
>>
>>  fail:
>
> --
> Regards,
>
> Laurent Pinchart
>
>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

RE: [PATCH] drm: rcar-du: track dma-buf fences

[Ucan, Emre (ADITG/ESB)]

Hello Laurent

Thank you for your review.

> -----Original Message-----
> From: Laurent Pinchart [mailto:laurent.pinchart@ideasonboard.com]
> Sent: Dienstag, 3. April 2018 20:53
> To: Ucan, Emre (ADITG/ESB)
> Cc: dri-devel@lists.freedesktop.org
> Subject: Re: [PATCH] drm: rcar-du: track dma-buf fences
> 
> Hello Emre,
> 
> Thank you for the patch.
> 
> On Tuesday, 3 April 2018 12:14:33 EEST Emre Ucan wrote:
> > We have to check dma-buf reservation objects
> > of our framebuffers before we use them.
> > Otherwise, another driver might be writing
> > on the same buffer which we are using.
> > This would cause visible tearing effects
> > on display.
> >
> > We can use existing atomic helper functions
> > to solve this problem.
> >
> > Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
> > ---
> >  drivers/gpu/drm/rcar-du/rcar_du_kms.c |  2 ++
> >  drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 20 ++++++++++++++++++++
> >  2 files changed, 22 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > b/drivers/gpu/drm/rcar-du/rcar_du_kms.c index 0329b35..f3da3d1 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > @@ -255,6 +255,8 @@ static void rcar_du_atomic_commit_tail(struct
> > drm_atomic_state *old_state) {
> >  	struct drm_device *dev = old_state->dev;
> >
> > +	drm_atomic_helper_wait_for_fences(dev, old_state, false);
> > +
> 
> The commit_tail() function in drm_atomic_helper.c, which calls our
> atomic_commit_tail() implementation, already calls
> drm_atomic_helper_wait_for_fences(). Why is there a need to duplicate the
> call
> here ?

You are right. I will remove it in second version.

> 
> >  	/* Apply the atomic update. */
> >  	drm_atomic_helper_commit_modeset_disables(dev, old_state);
> >  	drm_atomic_helper_commit_planes(dev, old_state,
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> > b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c index 2c260c3..482e23c 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> > @@ -18,12 +18,16 @@
> >  #include <drm/drm_fb_cma_helper.h>
> >  #include <drm/drm_gem_cma_helper.h>
> >  #include <drm/drm_plane_helper.h>
> > +#include <drm/drm_atomic.h>
> >
> >  #include <linux/bitops.h>
> >  #include <linux/dma-mapping.h>
> > +#include <linux/dma-fence.h>
> > +#include <linux/dma-buf.h>
> >  #include <linux/of_platform.h>
> >  #include <linux/scatterlist.h>
> >  #include <linux/videodev2.h>
> > +#include <linux/reservation.h>
> >
> >  #include <media/vsp1.h>
> >
> > @@ -203,6 +207,20 @@ static void rcar_du_vsp_plane_setup(struct
> > rcar_du_vsp_plane *plane) plane->index, &cfg);
> >  }
> >
> > +static void rcar_du_vsp_set_fence_for_plane(struct drm_plane_state
> *state)
> > +{
> > +	struct drm_gem_cma_object *gem;
> > +	struct dma_buf *dma_buf;
> > +	struct dma_fence *fence;
> > +
> > +	gem = drm_fb_cma_get_gem_obj(state->fb, 0);
> > +	dma_buf = gem->base.dma_buf;
> > +	if (dma_buf) {
> > +		fence = reservation_object_get_excl_rcu(dma_buf->resv);
> > +		drm_atomic_set_fence_for_plane(state, fence);
> 
> Unless I'm mistaken this is used for implicit fencing only. What is your use
> case, wouldn't it be better for userspace to use explicit fencing as that is
> the fence model that has been selected for display ?

We are using Weston on Renesas R-Car H3 SoC. I am using GPU rendered client buffers
directly as scanout buffer for the display. Weston is not using explicit fencing.

> 
> > +	}
> > +}
> 
> This looks very similar to drm_gem_fb_prepare_fb(), couldn't you use that
> function instead ?

Description of drm_gem_fb_prepare_fb() function states that it can be
used as the &drm_plane_helper_funcs.prepare_fb hook. But we have
our own hook function which is called rcar_du_vsp_plane_prepare_fb().
Therefore, I was not sure if it is correct to use drm_gem_fb_prepare_fb()
inside our hook function.

I will use it in the second version nevertheless.

> 
> >  static int rcar_du_vsp_plane_prepare_fb(struct drm_plane *plane,
> >  					struct drm_plane_state *state)
> >  {
> > @@ -237,6 +255,8 @@ static int rcar_du_vsp_plane_prepare_fb(struct
> drm_plane
> > *plane, }
> >  	}
> >
> > +	rcar_du_vsp_set_fence_for_plane(state);
> > +
> >  	return 0;
> >
> >  fail:
> 
> --
> Regards,
> 
> Laurent Pinchart
> 
> 

Best Regards,

Emre Ucan

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

RE: [PATCH] drm: rcar-du: track dma-buf fences

[Ucan, Emre (ADITG/ESB)]

Hello Laurent,

Thank you for your review.

Actually I sent this email yesterday. But  I don't see it in mailing list archives because of some reason.

> -----Original Message-----
> From: Laurent Pinchart [mailto:laurent.pinchart@ideasonboard.com]
> Sent: Dienstag, 3. April 2018 20:53
> To: Ucan, Emre (ADITG/ESB)
> Cc: dri-devel@lists.freedesktop.org
> Subject: Re: [PATCH] drm: rcar-du: track dma-buf fences
> 
> Hello Emre,
> 
> Thank you for the patch.
> 
> On Tuesday, 3 April 2018 12:14:33 EEST Emre Ucan wrote:
> > We have to check dma-buf reservation objects
> > of our framebuffers before we use them.
> > Otherwise, another driver might be writing
> > on the same buffer which we are using.
> > This would cause visible tearing effects
> > on display.
> >
> > We can use existing atomic helper functions
> > to solve this problem.
> >
> > Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
> > ---
> >  drivers/gpu/drm/rcar-du/rcar_du_kms.c |  2 ++
> >  drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 20 ++++++++++++++++++++
> >  2 files changed, 22 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > b/drivers/gpu/drm/rcar-du/rcar_du_kms.c index 0329b35..f3da3d1 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > @@ -255,6 +255,8 @@ static void rcar_du_atomic_commit_tail(struct
> > drm_atomic_state *old_state) {
> >  	struct drm_device *dev = old_state->dev;
> >
> > +	drm_atomic_helper_wait_for_fences(dev, old_state, false);
> > +
> 
> The commit_tail() function in drm_atomic_helper.c, which calls our
> atomic_commit_tail() implementation, already calls
> drm_atomic_helper_wait_for_fences(). Why is there a need to duplicate the
> call
> here ?

You are right. I will remove it in second version.

> 
> >  	/* Apply the atomic update. */
> >  	drm_atomic_helper_commit_modeset_disables(dev, old_state);
> >  	drm_atomic_helper_commit_planes(dev, old_state,
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> > b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c index 2c260c3..482e23c 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> > @@ -18,12 +18,16 @@
> >  #include <drm/drm_fb_cma_helper.h>
> >  #include <drm/drm_gem_cma_helper.h>
> >  #include <drm/drm_plane_helper.h>
> > +#include <drm/drm_atomic.h>
> >
> >  #include <linux/bitops.h>
> >  #include <linux/dma-mapping.h>
> > +#include <linux/dma-fence.h>
> > +#include <linux/dma-buf.h>
> >  #include <linux/of_platform.h>
> >  #include <linux/scatterlist.h>
> >  #include <linux/videodev2.h>
> > +#include <linux/reservation.h>
> >
> >  #include <media/vsp1.h>
> >
> > @@ -203,6 +207,20 @@ static void rcar_du_vsp_plane_setup(struct
> > rcar_du_vsp_plane *plane) plane->index, &cfg);
> >  }
> >
> > +static void rcar_du_vsp_set_fence_for_plane(struct drm_plane_state
> *state)
> > +{
> > +	struct drm_gem_cma_object *gem;
> > +	struct dma_buf *dma_buf;
> > +	struct dma_fence *fence;
> > +
> > +	gem = drm_fb_cma_get_gem_obj(state->fb, 0);
> > +	dma_buf = gem->base.dma_buf;
> > +	if (dma_buf) {
> > +		fence = reservation_object_get_excl_rcu(dma_buf->resv);
> > +		drm_atomic_set_fence_for_plane(state, fence);
> 
> Unless I'm mistaken this is used for implicit fencing only. What is your use
> case, wouldn't it be better for userspace to use explicit fencing as that is
> the fence model that has been selected for display ?

We are using Weston on Renesas R-Car H3 SoC. I am using GPU rendered client buffers
directly as scanout buffer for the display. Weston is not using explicit fencing.

> 
> > +	}
> > +}
> 
> This looks very similar to drm_gem_fb_prepare_fb(), couldn't you use that
> function instead ?

Description of drm_gem_fb_prepare_fb() function states that it can be
used as the &drm_plane_helper_funcs.prepare_fb hook. But we have
our own hook function which is called rcar_du_vsp_plane_prepare_fb().
Therefore, I was not sure if it is correct to use drm_gem_fb_prepare_fb()
inside our hook function.

I will use it in the second version nevertheless.

> 
> >  static int rcar_du_vsp_plane_prepare_fb(struct drm_plane *plane,
> >  					struct drm_plane_state *state)
> >  {
> > @@ -237,6 +255,8 @@ static int rcar_du_vsp_plane_prepare_fb(struct
> drm_plane
> > *plane, }
> >  	}
> >
> > +	rcar_du_vsp_set_fence_for_plane(state);
> > +
> >  	return 0;
> >
> >  fail:
> 
> --
> Regards,
> 
> Laurent Pinchart
> 
> 

Best Regards,

Emre Ucan

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH] drm: rcar-du: track dma-buf fences

[Daniel Vetter]

On Wed, Apr 4, 2018 at 12:59 PM, Ucan, Emre (ADITG/ESB)
<eucan@de.adit-jv.com> wrote:
> Hello Laurent
>
> Thank you for your review.
>
>> -----Original Message-----
>> From: Laurent Pinchart [mailto:laurent.pinchart@ideasonboard.com]
>> Sent: Dienstag, 3. April 2018 20:53
>> To: Ucan, Emre (ADITG/ESB)
>> Cc: dri-devel@lists.freedesktop.org
>> Subject: Re: [PATCH] drm: rcar-du: track dma-buf fences
>>
>> Hello Emre,
>>
>> Thank you for the patch.
>>
>> On Tuesday, 3 April 2018 12:14:33 EEST Emre Ucan wrote:
>> > We have to check dma-buf reservation objects
>> > of our framebuffers before we use them.
>> > Otherwise, another driver might be writing
>> > on the same buffer which we are using.
>> > This would cause visible tearing effects
>> > on display.
>> >
>> > We can use existing atomic helper functions
>> > to solve this problem.
>> >
>> > Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
>> > ---
>> >  drivers/gpu/drm/rcar-du/rcar_du_kms.c |  2 ++
>> >  drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 20 ++++++++++++++++++++
>> >  2 files changed, 22 insertions(+)
>> >
>> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> > b/drivers/gpu/drm/rcar-du/rcar_du_kms.c index 0329b35..f3da3d1 100644
>> > --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> > @@ -255,6 +255,8 @@ static void rcar_du_atomic_commit_tail(struct
>> > drm_atomic_state *old_state) {
>> >     struct drm_device *dev = old_state->dev;
>> >
>> > +   drm_atomic_helper_wait_for_fences(dev, old_state, false);
>> > +
>>
>> The commit_tail() function in drm_atomic_helper.c, which calls our
>> atomic_commit_tail() implementation, already calls
>> drm_atomic_helper_wait_for_fences(). Why is there a need to duplicate the
>> call
>> here ?
>
> You are right. I will remove it in second version.

You can use it in your own hook. Patch to update the kerneldoc to
clarify that would be great.
-Daniel

>
>>
>> >     /* Apply the atomic update. */
>> >     drm_atomic_helper_commit_modeset_disables(dev, old_state);
>> >     drm_atomic_helper_commit_planes(dev, old_state,
>> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
>> > b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c index 2c260c3..482e23c 100644
>> > --- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
>> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
>> > @@ -18,12 +18,16 @@
>> >  #include <drm/drm_fb_cma_helper.h>
>> >  #include <drm/drm_gem_cma_helper.h>
>> >  #include <drm/drm_plane_helper.h>
>> > +#include <drm/drm_atomic.h>
>> >
>> >  #include <linux/bitops.h>
>> >  #include <linux/dma-mapping.h>
>> > +#include <linux/dma-fence.h>
>> > +#include <linux/dma-buf.h>
>> >  #include <linux/of_platform.h>
>> >  #include <linux/scatterlist.h>
>> >  #include <linux/videodev2.h>
>> > +#include <linux/reservation.h>
>> >
>> >  #include <media/vsp1.h>
>> >
>> > @@ -203,6 +207,20 @@ static void rcar_du_vsp_plane_setup(struct
>> > rcar_du_vsp_plane *plane) plane->index, &cfg);
>> >  }
>> >
>> > +static void rcar_du_vsp_set_fence_for_plane(struct drm_plane_state
>> *state)
>> > +{
>> > +   struct drm_gem_cma_object *gem;
>> > +   struct dma_buf *dma_buf;
>> > +   struct dma_fence *fence;
>> > +
>> > +   gem = drm_fb_cma_get_gem_obj(state->fb, 0);
>> > +   dma_buf = gem->base.dma_buf;
>> > +   if (dma_buf) {
>> > +           fence = reservation_object_get_excl_rcu(dma_buf->resv);
>> > +           drm_atomic_set_fence_for_plane(state, fence);
>>
>> Unless I'm mistaken this is used for implicit fencing only. What is your use
>> case, wouldn't it be better for userspace to use explicit fencing as that is
>> the fence model that has been selected for display ?
>
> We are using Weston on Renesas R-Car H3 SoC. I am using GPU rendered client buffers
> directly as scanout buffer for the display. Weston is not using explicit fencing.
>
>>
>> > +   }
>> > +}
>>
>> This looks very similar to drm_gem_fb_prepare_fb(), couldn't you use that
>> function instead ?
>
> Description of drm_gem_fb_prepare_fb() function states that it can be
> used as the &drm_plane_helper_funcs.prepare_fb hook. But we have
> our own hook function which is called rcar_du_vsp_plane_prepare_fb().
> Therefore, I was not sure if it is correct to use drm_gem_fb_prepare_fb()
> inside our hook function.
>
> I will use it in the second version nevertheless.
>
>>
>> >  static int rcar_du_vsp_plane_prepare_fb(struct drm_plane *plane,
>> >                                     struct drm_plane_state *state)
>> >  {
>> > @@ -237,6 +255,8 @@ static int rcar_du_vsp_plane_prepare_fb(struct
>> drm_plane
>> > *plane, }
>> >     }
>> >
>> > +   rcar_du_vsp_set_fence_for_plane(state);
>> > +
>> >     return 0;
>> >
>> >  fail:
>>
>> --
>> Regards,
>>
>> Laurent Pinchart
>>
>>
>
> Best Regards,
>
> Emre Ucan
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel