[PATCH] drm/radeon: Read back ring buffer before updating WPTR

[Alex Deucher]

On Fri, Aug 8, 2014 at 4:45 AM, Michel Dänzer <michel at daenzer.net> wrote:
> From: Michel Dänzer <michel.daenzer at amd.com>
>
> This fixes a ring test failure reported on a Kabini system which was
> triggered by write-combined CPU mappings of the ring buffers.
>
> Reported-and-Tested-by: Will Trives <renevant at internode.on.net>
> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>

Applied to my fixes tree.

Alex

> ---
>  drivers/gpu/drm/radeon/radeon_ring.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_ring.c b/drivers/gpu/drm/radeon/radeon_ring.c
> index 5b4e0cf..6dff529 100644
> --- a/drivers/gpu/drm/radeon/radeon_ring.c
> +++ b/drivers/gpu/drm/radeon/radeon_ring.c
> @@ -193,6 +193,10 @@ void radeon_ring_commit(struct radeon_device *rdev, struct radeon_ring *ring)
>                 radeon_ring_write(ring, ring->nop);
>         }
>         mb();
> +       /* This is necessary to prevent ring test failures on some systems
> +        * with write-combined CPU mappings of the ring buffers
> +        */
> +       (void)ring->ring[ring->wptr];
>         /* If we are emitting the HDP flush via MMIO, we need to do it after
>          * all CPU writes to VRAM finished.
>          */
> --
> 2.0.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel