[PATCH 1/4] drm/i915/fb: Relax clear color alignment to 64 bytes

[Xi Ruoyao]

On Fri, 2024-11-29 at 08:50 +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Mesa changed its clear color alignment from 4k to 64 bytes
> without informing the kernel side about the change. This
> is now likely to cause framebuffer creation to fail.
> 
> The only thing we do with the clear color buffer in i915 is:
> 1. map a single page
> 2. read out bytes 16-23 from said page
> 3. unmap the page
> 
> So the only requirement we really have is that those 8 bytes
> are all contained within one page. Thus we can deal with the
> Mesa regression by reducing the alignment requiment from 4k
> to the same 64 bytes in the kernel. We could even go as low as
> 32 bytes, but IIRC 64 bytes is the hardware requirement on
> the 3D engine side so matching that seems sensible.
> 
> Cc: stable at vger.kernel.org
> Cc: Sagar Ghuge <sagar.ghuge at intel.com>
> Cc: Nanley Chery <nanley.g.chery at intel.com>
> Reported-by: Xi Ruoyao <xry111 at xry111.site>
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13057
> Closes: https://lore.kernel.org/all/45a5bba8de009347262d86a4acb27169d9ae0d9f.camel@xry111.site/
> Link: https://gitlab.freedesktop.org/mesa/mesa/-/commit/17f97a69c13832a6c1b0b3aad45b06f07d4b852f
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Tested-by: Xi Ruoyao <xry111 at xry111.site>

> ---
>  drivers/gpu/drm/i915/display/intel_fb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fb.c b/drivers/gpu/drm/i915/display/intel_fb.c
> index 6a7060889f40..223c4218c019 100644
> --- a/drivers/gpu/drm/i915/display/intel_fb.c
> +++ b/drivers/gpu/drm/i915/display/intel_fb.c
> @@ -1694,7 +1694,7 @@ int intel_fill_fb_info(struct drm_i915_private *i915, struct intel_framebuffer *
>  		 * arithmetic related to alignment and offset calculation.
>  		 */
>  		if (is_gen12_ccs_cc_plane(&fb->base, i)) {
> -			if (IS_ALIGNED(fb->base.offsets[i], PAGE_SIZE))
> +			if (IS_ALIGNED(fb->base.offsets[i], 64))
>  				continue;
>  			else
>  				return -EINVAL;

-- 
Xi Ruoyao <xry111 at xry111.site>
School of Aerospace Science and Technology, Xidian University