[Intel-gfx] [PATCH 1/6] drm/i915: Fail if we can't get a fence for gen2/3 tiled scanout

[Chris Wilson]

Quoting Ville Syrjala (2018-02-21 16:02:30)
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Gen2/3 display engine depends on the fence for tiled scanout. So if we
> fail to get a fence fail the entire operation.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 5d46771d58f6..66b269bc24b9 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2123,6 +2123,8 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
>                 goto err;
>  
>         if (i915_vma_is_map_and_fenceable(vma)) {
> +               int ret;
> +
>                 /* Install a fence for tiled scan-out. Pre-i965 always needs a
>                  * fence, whereas 965+ only requires a fence if using
>                  * framebuffer compression.  For simplicity, we always, when
> @@ -2139,7 +2141,13 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
>                  * something and try to run the system in a "less than optimal"
>                  * mode that matches the user configuration.
>                  */
> -               if (i915_vma_pin_fence(vma) == 0 && vma->fence)
> +               ret = i915_vma_pin_fence(vma);
> +               if (ret != 0 && INTEL_GEN(dev_priv) < 4) {
> +                       vma = ERR_PTR(ret);
> +                       goto err;
> +               }
> +
> +               if (ret == 0 && vma->fence)
>                         *out_flags |= PLANE_HAS_FENCE;
>         }

Ok, I'd like to see INTEL_GEN(dev_priv) < 4 be replaced with say
needs_fence (and may be passed in from the caller like wants_fence?).
Then I'm wondering if a 
	if (WARN_ON(needs_fence && !(*flags & PLANE_HAS_FENCE))
makes sense.

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris