Re: [Intel-gfx] [PATCH v5 4/5] drm/i915/display: consider DG2_RC_CCS_CC when migrating buffers

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

Hi Matt,

On 04/10/2022 14:19, Matthew Auld wrote:
> For these types of display buffers, we need to able to CPU access some
> part of the backing memory in prepare_plane_clear_colors(). As a result
> we need to ensure we always place in the mappable part of lmem, which
> becomes necessary on small-bar systems.
> 
> v2(Nirmoy & Ville):
>   - Add some commentary for why we need to CPU access the buffer.
>   - Split out the other changes, so we just consider the display change
>     here.
> v3:
>   - Handle this in the dpt path.
> v4(Ville):
>   - Drop the intel_fb_rc_ccs_cc_plane() sanity check in
>     pin_and_fence_fb_obj(), since we can also trigger this on DG1 it
>     seems.
> 
> Fixes: eb1c535f0d69 ("drm/i915: turn on small BAR support")

That one landed in 6.0 - do you want to send this (with 
pre-requisite(s)) to stable? Or if not do you want me to send for 6.1 as 
part of fixes flow? In which case what are the per-requisites?

Regards,

Tvrtko

> Reported-by: Jianshui Yu <jianshui.yu@intel.com>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Nirmoy Das <nirmoy.das@intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_fb_pin.c | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fb_pin.c b/drivers/gpu/drm/i915/display/intel_fb_pin.c
> index 5031ee5695dd..e12339f46640 100644
> --- a/drivers/gpu/drm/i915/display/intel_fb_pin.c
> +++ b/drivers/gpu/drm/i915/display/intel_fb_pin.c
> @@ -50,7 +50,18 @@ intel_pin_fb_obj_dpt(struct drm_framebuffer *fb,
>   			continue;
>   
>   		if (HAS_LMEM(dev_priv)) {
> -			ret = i915_gem_object_migrate(obj, &ww, INTEL_REGION_LMEM_0);
> +			unsigned int flags = obj->flags;
> +
> +			/*
> +			 * For this type of buffer we need to able to read from the CPU
> +			 * the clear color value found in the buffer, hence we need to
> +			 * ensure it is always in the mappable part of lmem, if this is
> +			 * a small-bar device.
> +			 */
> +			if (intel_fb_rc_ccs_cc_plane(fb) >= 0)
> +				flags &= ~I915_BO_ALLOC_GPU_ONLY;
> +			ret = __i915_gem_object_migrate(obj, &ww, INTEL_REGION_LMEM_0,
> +							flags);
>   			if (ret)
>   				continue;
>   		}