Re: [PATCH 3/6] drm/i915/fbdev: Extract intel_fbdev_fb_prefer_stolen()

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

On Thu, 05 Feb 2026, Vinod Govindapillai <vinod.govindapillai@intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Consolidate the "should we allocate fbdev fb in stolen?"
> check into a helper function. Makes it easier to change the
> heuristics without having to change so many places.
>
> v2: rebase related changes and consolidate all the prefer
>     stolen conditions into a single function (Vinod)
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_fbdev_fb.c | 27 +++++++++++++------
>  drivers/gpu/drm/i915/display/intel_fbdev_fb.h |  2 ++
>  drivers/gpu/drm/i915/i915_initial_plane.c     |  3 ++-

All of these files are built on i915 only...

>  3 files changed, 23 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev_fb.c b/drivers/gpu/drm/i915/display/intel_fbdev_fb.c
> index e5251ed15948..4f057dbd1279 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev_fb.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev_fb.c
> @@ -10,6 +10,7 @@
>  #include "gem/i915_gem_lmem.h"
>  
>  #include "i915_drv.h"
> +#include "intel_display_core.h"

...and should not include intel_display_core.h.

This is non-obvious, and an easy mistake to make. Eventually
intel_fbdev_fb.c needs to move to i915 core, with some refactoring.

>  #include "intel_fbdev_fb.h"
>  
>  u32 intel_fbdev_fb_pitch_align(u32 stride)
> @@ -17,6 +18,23 @@ u32 intel_fbdev_fb_pitch_align(u32 stride)
>  	return ALIGN(stride, 64);
>  }
>  
> +bool intel_fbdev_fb_prefer_stolen(struct intel_display *display,

Just pass struct drm_i915_private around here.

> +				  unsigned int size)
> +{
> +	struct drm_i915_private *i915 = to_i915(display->drm);
> +
> +	/* Skip stolen on MTL as Wa_22018444074 mitigation. */
> +	if (IS_METEORLAKE(i915))
> +		return false;
> +
> +	/*
> +	 * If the FB is too big, just don't use it since fbdev is not very
> +	 * important and we should probably use that space with FBC or other
> +	 * features.
> +	 */
> +	return i915->dsm.usable_size >= size * 2;
> +}
> +
>  struct drm_gem_object *intel_fbdev_fb_bo_create(struct drm_device *drm, int size)
>  {
>  	struct drm_i915_private *i915 = to_i915(drm);
> @@ -28,14 +46,7 @@ struct drm_gem_object *intel_fbdev_fb_bo_create(struct drm_device *drm, int size
>  						  I915_BO_ALLOC_CONTIGUOUS |
>  						  I915_BO_ALLOC_USER);
>  	} else {
> -		/*
> -		 * If the FB is too big, just don't use it since fbdev is not very
> -		 * important and we should probably use that space with FBC or other
> -		 * features.
> -		 *
> -		 * Also skip stolen on MTL as Wa_22018444074 mitigation.
> -		 */
> -		if (!IS_METEORLAKE(i915) && size * 2 < i915->dsm.usable_size)
> +		if (intel_fbdev_fb_prefer_stolen(i915->display, size))
>  			obj = i915_gem_object_create_stolen(i915, size);
>  		if (IS_ERR(obj))
>  			obj = i915_gem_object_create_shmem(i915, size);
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev_fb.h b/drivers/gpu/drm/i915/display/intel_fbdev_fb.h
> index fd0b3775dc1f..82da57601dc7 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev_fb.h
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev_fb.h
> @@ -13,11 +13,13 @@ struct drm_gem_object;
>  struct drm_mode_fb_cmd2;
>  struct fb_info;
>  struct i915_vma;
> +struct intel_display;
>  
>  u32 intel_fbdev_fb_pitch_align(u32 stride);
>  struct drm_gem_object *intel_fbdev_fb_bo_create(struct drm_device *drm, int size);
>  void intel_fbdev_fb_bo_destroy(struct drm_gem_object *obj);
>  int intel_fbdev_fb_fill_info(struct drm_device *drm, struct fb_info *info,
>  			     struct drm_gem_object *obj, struct i915_vma *vma);
> +bool intel_fbdev_fb_prefer_stolen(struct intel_display *display, unsigned int size);
>  
>  #endif
> diff --git a/drivers/gpu/drm/i915/i915_initial_plane.c b/drivers/gpu/drm/i915/i915_initial_plane.c
> index 7fb52d81f7b6..1263d7db2c44 100644
> --- a/drivers/gpu/drm/i915/i915_initial_plane.c
> +++ b/drivers/gpu/drm/i915/i915_initial_plane.c
> @@ -9,6 +9,7 @@
>  #include "display/intel_crtc.h"
>  #include "display/intel_display_types.h"
>  #include "display/intel_fb.h"
> +#include "display/intel_fbdev_fb.h"
>  #include "gem/i915_gem_lmem.h"
>  #include "gem/i915_gem_region.h"
>  
> @@ -116,7 +117,7 @@ initial_plane_vma(struct drm_i915_private *i915,
>  	 */
>  	if (IS_ENABLED(CONFIG_FRAMEBUFFER_CONSOLE) &&
>  	    mem == i915->mm.stolen_region &&
> -	    size * 2 > i915->dsm.usable_size) {
> +	    !intel_fbdev_fb_prefer_stolen(i915->display, size)) {
>  		drm_dbg_kms(&i915->drm, "Initial FB size exceeds half of stolen, discarding\n");
>  		return NULL;
>  	}

-- 
Jani Nikula, Intel