[Intel-gfx] [PATCH 1/2] drm/i915: Add display WA #1175 for planes ending close to right screen edge

[Chris Wilson]

Quoting Imre Deak (2018-01-12 14:54:36)
> As described in the WA on GLK and CNL planes on the right edge of the
> screen that have less than 4 pixels visible from the beginning of the
> plane to the edge of the screen can cause FIFO underflow and display
> corruption.
> 
> On GLK/CNL I could trigger the problem only if the plane was at the same
> time also aligned to the top edge of the screen (after clipping) and
> there were exactly 2 pixels visible from the start of the plane to the
> right edge of the screen (so couldn't trigger it with 1 or 3 pixels
> visible). Nevertheless, to be sure, I also applied the WA for these cases.
> 
> I also couldn't see any problem with the cursor plane and later Art
> confirmed that it's not affected, so the WA is applied only for the
> other plane types.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 28 ++++++++++++++++++++++++----
>  drivers/gpu/drm/i915/intel_drv.h     |  3 ++-
>  drivers/gpu/drm/i915/intel_sprite.c  |  2 +-
>  3 files changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 221e3a183d36..3d931b652795 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2917,14 +2917,19 @@ static bool skl_check_main_ccs_coordinates(struct intel_plane_state *plane_state
>         return true;
>  }
>  
> -static int skl_check_main_surface(struct intel_plane_state *plane_state)
> +static int skl_check_main_surface(const struct intel_crtc_state *crtc_state,
> +                                 struct intel_plane_state *plane_state)
>  {
> +       struct drm_i915_private *dev_priv =
> +               to_i915(plane_state->base.plane->dev);
>         const struct drm_framebuffer *fb = plane_state->base.fb;
>         unsigned int rotation = plane_state->base.rotation;
>         int x = plane_state->base.src.x1 >> 16;
>         int y = plane_state->base.src.y1 >> 16;
>         int w = drm_rect_width(&plane_state->base.src) >> 16;
>         int h = drm_rect_height(&plane_state->base.src) >> 16;
> +       int dst_x = plane_state->base.dst.x1;
> +       int pipe_src_w = crtc_state->pipe_src_w;
>         int max_width = skl_max_plane_width(fb, 0, rotation);
>         int max_height = 4096;
>         u32 alignment, offset, aux_offset = plane_state->aux.offset;
> @@ -2935,6 +2940,20 @@ static int skl_check_main_surface(struct intel_plane_state *plane_state)
>                 return -EINVAL;
>         }
>  
> +       /*
> +        * Display WA #1175: cnl,glk
> +        * Planes other than the cursor may cause FIFO underflow and display
> +        * corruption if starting less than 4 pixels from the right edge of
> +        * the screen.
> +        */
> +       if ((IS_GEMINILAKE(dev_priv) || IS_CANNONLAKE(dev_priv)) &&
> +           dst_x > pipe_src_w - 4) {
> +               DRM_DEBUG_KMS("requested plane X start position %d invalid (valid range %d-%d)\n",
> +                             dst_x,
> +                             0, pipe_src_w - 4);

You are rejecting user input, so this should be DRM_DEBUG() (or whatever
the future user channel will be).
-Chris