Re: [PATCH 04/11] drm/i915: Introduce pin_params.needs_cpu_lmem_access

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 16 Apr 2026, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Add a new flag pin_params.neeeds_cpu_lmem_access so that the
> low level pinning code doesn't need to peek into the display
> driver's framebuffer structure.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_fb_pin.h | 1 +
>  drivers/gpu/drm/i915/i915_fb_pin.c          | 4 +++-
>  drivers/gpu/drm/xe/display/xe_fb_pin.c      | 3 ++-
>  3 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_fb_pin.h b/drivers/gpu/drm/i915/display/intel_fb_pin.h
> index e6271437459d..bcf5a1f46092 100644
> --- a/drivers/gpu/drm/i915/display/intel_fb_pin.h
> +++ b/drivers/gpu/drm/i915/display/intel_fb_pin.h
> @@ -19,6 +19,7 @@ struct intel_fb_pin_params {
>  	unsigned int alignment;
>  	unsigned int phys_alignment;
>  	unsigned int vtd_guard;
> +	bool needs_cpu_lmem_access;
>  };
>  
>  struct i915_vma *
> diff --git a/drivers/gpu/drm/i915/i915_fb_pin.c b/drivers/gpu/drm/i915/i915_fb_pin.c
> index 780be25ad43b..96ffc4b0d809 100644
> --- a/drivers/gpu/drm/i915/i915_fb_pin.c
> +++ b/drivers/gpu/drm/i915/i915_fb_pin.c
> @@ -61,7 +61,7 @@ intel_fb_pin_to_dpt(const struct drm_framebuffer *fb,
>  			 * ensure it is always in the mappable part of lmem, if this is
>  			 * a small-bar device.
>  			 */
> -			if (intel_fb_needs_cpu_access(fb))
> +			if (pin_params->needs_cpu_lmem_access)
>  				flags &= ~I915_BO_ALLOC_GPU_ONLY;
>  			ret = __i915_gem_object_migrate(obj, &ww, INTEL_REGION_LMEM_0,
>  							flags);
> @@ -275,6 +275,7 @@ int intel_plane_pin_fb(struct intel_plane_state *plane_state,
>  			.alignment = intel_plane_fb_min_alignment(plane_state),
>  			.phys_alignment = intel_plane_fb_min_phys_alignment(plane_state),
>  			.vtd_guard = intel_plane_fb_vtd_guard(plane_state),
> +			.needs_cpu_lmem_access = intel_fb_needs_cpu_access(&fb->base),

IIUC this path never uses .needs_cpu_lmem_access, but you initialize it
anyway. What I find confusing is initializing it here apparently
unnecessarily, but then leaving it out on a number of other paths that
don't need it.

Other than that,

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

>  		};
>  		int fence_id = -1;
>  
> @@ -289,6 +290,7 @@ int intel_plane_pin_fb(struct intel_plane_state *plane_state,
>  		struct intel_fb_pin_params pin_params = {
>  			.view = &plane_state->view.gtt,
>  			.alignment = intel_plane_fb_min_alignment(plane_state),
> +			.needs_cpu_lmem_access = intel_fb_needs_cpu_access(&fb->base),
>  		};
>  
>  		vma = i915_dpt_pin_to_ggtt(fb->dpt, pin_params.alignment / 512);
> diff --git a/drivers/gpu/drm/xe/display/xe_fb_pin.c b/drivers/gpu/drm/xe/display/xe_fb_pin.c
> index 205492639dba..a4eb06cfa769 100644
> --- a/drivers/gpu/drm/xe/display/xe_fb_pin.c
> +++ b/drivers/gpu/drm/xe/display/xe_fb_pin.c
> @@ -335,7 +335,7 @@ static struct i915_vma *__xe_pin_fb_vma(const struct intel_framebuffer *fb,
>  
>  	refcount_set(&vma->ref, 1);
>  	if (IS_DGFX(to_xe_device(bo->ttm.base.dev)) &&
> -	    intel_fb_needs_cpu_access(&fb->base) &&
> +	    pin_params->needs_cpu_lmem_access &&
>  	    !(bo->flags & XE_BO_FLAG_NEEDS_CPU_ACCESS)) {
>  		struct xe_vram_region *vram = xe_device_get_root_tile(xe)->mem.vram;
>  
> @@ -474,6 +474,7 @@ int intel_plane_pin_fb(struct intel_plane_state *new_plane_state,
>  	struct intel_fb_pin_params pin_params = {
>  		.view = &new_plane_state->view.gtt,
>  		.alignment = plane->min_alignment(plane, fb, 0),
> +		.needs_cpu_lmem_access = intel_fb_needs_cpu_access(fb),
>  	};
>  
>  	if (reuse_vma(new_plane_state, old_plane_state))

-- 
Jani Nikula, Intel