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

Jani Nikula
2026-04-17T09:39:59Z

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