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