RE: [PATCH v2 5/5] drm/i915: Introduce intel_bo_fbdev_bios_fb_takeover()

> -----Original Message-----
> From: Intel-xe <[email protected]> On Behalf Of Maarten
> Lankhorst
> Sent: Tuesday, July 21, 2026 7:56 PM
> To: [email protected]
> Cc: [email protected]; Maarten Lankhorst <[email protected]>; Ville
> Syrjälä <[email protected]>
> Subject: [PATCH v2 5/5] drm/i915: Introduce intel_bo_fbdev_bios_fb_takeover()
> 
> Pull the "do we want to use stolen for the BIOS FB?" checks into a new
> intel_bo_fbdev_bios_fb_takeover() helper, and defer that decision until we're ready
> to reallocate the fbdev FB. This way even if we don't want to ultimately use the
> BIOS FB we'll keep the plane enabled until the replacement FB is ready. Should
> hopefully result in fewer display blinks during boot.
> 
> Additionally, on some platforms this allows us to re-create the framebuffer when
> stolen memory is not suitable, using the blitter engine to copy the contents to
> system memory without causing any flickering by not preserving the stolen
> memory allocation.
> 
> Based on a similar patch by Ville, that introduced intel_bo_fbdev_bios_fb_ok().

Looks Good to me.
Reviewed-by: Uma Shankar <[email protected]>

Please get an ack from someone from Core KMD as well.

@B S, Karthik Can we ask someone to check and give a Tested-by from validation
side for this series.

Regards,
Uma Shankar

> Cc: Ville Syrjälä <[email protected]>
> Signed-off-by: Maarten Lankhorst <[email protected]>
> ---
>  drivers/gpu/drm/i915/display/intel_bo.c       |  7 ++
>  drivers/gpu/drm/i915/display/intel_bo.h       |  1 +
>  drivers/gpu/drm/i915/display/intel_fbdev.c    | 68 ++++++++++++++++---
>  drivers/gpu/drm/i915/i915_bo.c                | 14 +++-
>  drivers/gpu/drm/i915/i915_bo.h                |  6 --
>  drivers/gpu/drm/i915/i915_initial_plane.c     | 14 ----
>  drivers/gpu/drm/xe/display/xe_display_bo.c    | 56 ++++++++++++++-
>  drivers/gpu/drm/xe/display/xe_display_bo.h    |  6 --
>  drivers/gpu/drm/xe/display/xe_initial_plane.c |  8 ---
> include/drm/intel/display_parent_interface.h  |  1 +
>  10 files changed, 134 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_bo.c
> b/drivers/gpu/drm/i915/display/intel_bo.c
> index 8ecdbb7e39f3d..878c62cb48b4f 100644
> --- a/drivers/gpu/drm/i915/display/intel_bo.c
> +++ b/drivers/gpu/drm/i915/display/intel_bo.c
> @@ -92,6 +92,13 @@ u32 intel_bo_fbdev_pitch_align(struct intel_display
> *display, u32 stride)
>  	return display->parent->bo->fbdev_pitch_align(stride);
>  }
> 
> +struct drm_gem_object *intel_bo_fbdev_bios_fb_takeover(struct
> +drm_gem_object *obj) {
> +	struct intel_display *display = to_intel_display(obj->dev);
> +
> +	return display->parent->bo->fbdev_bios_fb_takeover(obj);
> +}
> +
>  struct drm_gem_object *intel_bo_fbdev_create(struct intel_display *display, int
> size)  {
>  	return display->parent->bo->fbdev_create(display->drm, size); diff --git
> a/drivers/gpu/drm/i915/display/intel_bo.h b/drivers/gpu/drm/i915/display/intel_bo.h
> index 348f7fa669608..0410ee9c6d2e1 100644
> --- a/drivers/gpu/drm/i915/display/intel_bo.h
> +++ b/drivers/gpu/drm/i915/display/intel_bo.h
> @@ -34,6 +34,7 @@ struct drm_gem_object *intel_bo_framebuffer_lookup(struct
> intel_display *display
>  						   const struct
> drm_mode_fb_cmd2 *user_mode_cmd);
> 
>  u32 intel_bo_fbdev_pitch_align(struct intel_display *display, u32 stride);
> +struct drm_gem_object *intel_bo_fbdev_bios_fb_takeover(struct
> +drm_gem_object *obj);
>  struct drm_gem_object *intel_bo_fbdev_create(struct intel_display *display, int
> size);  void intel_bo_fbdev_destroy(struct drm_gem_object *obj);  int
> intel_bo_fbdev_fill_info(struct drm_gem_object *obj, struct fb_info *info, diff --git
> a/drivers/gpu/drm/i915/display/intel_fbdev.c
> b/drivers/gpu/drm/i915/display/intel_fbdev.c
> index db0e36dd8722f..aac35b1ec0306 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> @@ -225,11 +225,11 @@ static void intel_fbdev_fill_mode_cmd(struct
> intel_display *display,
> 
>  static struct intel_framebuffer *
>  __intel_fbdev_fb_alloc(struct intel_display *display,
> -		       struct drm_fb_helper_surface_size *sizes)
> +		       struct drm_fb_helper_surface_size *sizes,
> +		       struct drm_gem_object *obj)
>  {
>  	struct drm_mode_fb_cmd2 mode_cmd = {};
>  	struct drm_framebuffer *fb;
> -	struct drm_gem_object *obj;
>  	int size;
> 
>  	intel_fbdev_fill_mode_cmd(display, sizes, &mode_cmd); @@ -262,32
> +262,68 @@ __intel_fbdev_fb_alloc(struct intel_display *display,
> 
>  }
> 
> -static bool bios_fb_ok(const struct intel_framebuffer *fb,
> -		       const struct drm_fb_helper_surface_size *sizes)
> +static struct intel_framebuffer *
> +__intel_fbdev_fb_realloc(struct intel_display *display,
> +			 const struct drm_framebuffer *orig_fb,
> +			 struct drm_gem_object *obj)
> +{
> +	struct drm_framebuffer *new_fb;
> +	struct drm_mode_fb_cmd2 mode_cmd = {
> +		.flags = DRM_MODE_FB_MODIFIERS,
> +		.width = orig_fb->width,
> +		.height = orig_fb->height,
> +		.pitches[0] = orig_fb->pitches[0],
> +		.offsets[0] = orig_fb->offsets[0],
> +		.pixel_format = orig_fb->format->format,
> +		.modifier[0] = orig_fb->modifier,
> +	};
> +
> +	new_fb = intel_framebuffer_create(obj, orig_fb->format, &mode_cmd);
> +
> +	if (IS_ERR(new_fb)) {
> +		intel_bo_fbdev_destroy(obj);
> +		return ERR_CAST(new_fb);
> +	}
> +
> +	drm_gem_object_put(obj);
> +	return to_intel_framebuffer(new_fb);
> +}
> +
> +static struct intel_framebuffer *bios_fb_pick(struct intel_framebuffer *fb,
> +					      const struct
> drm_fb_helper_surface_size *sizes)
>  {
>  	struct intel_display *display = to_intel_display(fb->base.dev);
>  	int width = fb->base.width;
>  	int height = fb->base.height;
>  	int depth = fb->base.format->depth;
>  	int bpp = fb->base.format->cpp[0] * 8;
> +	struct drm_gem_object *new;
> 
>  	if (sizes->fb_width > width || sizes->fb_height > height) {
>  		drm_dbg_kms(display->drm,
>  			    "BIOS fb too small (%dx%d), we require (%dx%d),
> releasing it\n",
>  			    width, height, sizes->fb_width, sizes->fb_height);
> -		return false;
> +		return NULL;
>  	}
> 
>  	if (sizes->surface_depth != depth || sizes->surface_bpp != bpp) {
>  		drm_dbg_kms(display->drm,
>  			    "BIOS fb using wrong depth/bpp (%d/%d), we require
> (%d/%d), releasing it\n",
>  			    depth, bpp, sizes->surface_depth, sizes-
> >surface_bpp);
> -		return false;
> +		return NULL;
>  	}
> 
> -	return true;
> +	new = intel_bo_fbdev_bios_fb_takeover(fb->base.obj[0]);
> +	if (IS_ERR(new))
> +		return ERR_CAST(new);
> +	if (fb->base.obj[0] == new)
> +		return fb;
> +
> +	/* Different object, re-create an intel_framebuffer around it */
> +	return __intel_fbdev_fb_realloc(display, &fb->base, new);
>  }
> 
> +
>  int intel_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
>  				   struct drm_fb_helper_surface_size *sizes)  {
> @@ -305,9 +341,19 @@ int intel_fbdev_driver_fbdev_probe(struct drm_fb_helper
> *helper,
> 
>  	ifbdev->fb = NULL;
> 
> -	if (fb && !bios_fb_ok(fb, sizes)) {
> -		drm_framebuffer_put(&fb->base);
> -		fb = NULL;
> +	if (fb) {
> +		struct intel_framebuffer *bios_fb =
> +			bios_fb_pick(fb, sizes);
> +
> +		if (IS_ERR(bios_fb)) {
> +			drm_dbg_kms(display->drm, "Re-using BIOS fb failed
> (%pe).", bios_fb);
> +			bios_fb = NULL;
> +		}
> +
> +		if (fb != bios_fb) {
> +			drm_framebuffer_put(&fb->base);
> +			fb = bios_fb;
> +		}
>  	}
> 
>  	wakeref = intel_display_rpm_get(display); @@ -316,7 +362,7 @@ int
> intel_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
>  		drm_dbg_kms(display->drm,
>  			    "no BIOS fb, allocating a new one\n");
> 
> -		fb = __intel_fbdev_fb_alloc(display, sizes);
> +		fb = __intel_fbdev_fb_alloc(display, sizes, NULL);
>  		if (IS_ERR(fb)) {
>  			ret = PTR_ERR(fb);
>  			goto out_unlock;
> diff --git a/drivers/gpu/drm/i915/i915_bo.c b/drivers/gpu/drm/i915/i915_bo.c index
> 559341103ca7d..fe11c0be81013 100644
> --- a/drivers/gpu/drm/i915/i915_bo.c
> +++ b/drivers/gpu/drm/i915/i915_bo.c
> @@ -150,7 +150,7 @@ static u32 i915_bo_fbdev_pitch_align(u32 stride)
>  	return ALIGN(stride, 64);
>  }
> 
> -bool i915_bo_fbdev_prefer_stolen(struct drm_i915_private *i915, unsigned int
> size)
> +static bool i915_bo_fbdev_prefer_stolen(struct drm_i915_private *i915,
> +unsigned int size)
>  {
>  	/* Skip stolen on MTL as Wa_22018444074 mitigation. */
>  	if (IS_METEORLAKE(i915))
> @@ -164,6 +164,17 @@ bool i915_bo_fbdev_prefer_stolen(struct
> drm_i915_private *i915, unsigned int siz
>  	return i915->dsm.usable_size >= size * 2;  }
> 
> +static struct drm_gem_object *i915_bo_fbdev_bios_fb_takeover(struct
> +drm_gem_object *obj) {
> +	struct drm_i915_private *i915 = to_i915(obj->dev);
> +
> +	if (HAS_LMEM(i915) ||
> +	    i915_bo_fbdev_prefer_stolen(i915, obj->size))
> +		return obj;
> +
> +	return ERR_PTR(-EIO);
> +}
> +
>  static struct drm_gem_object *i915_bo_fbdev_create(struct drm_device *drm, int
> size)  {
>  	struct drm_i915_private *i915 = to_i915(drm); @@ -262,6 +273,7 @@
> const struct intel_display_bo_interface i915_display_bo_interface = {
>  	.framebuffer_fini = i915_bo_framebuffer_fini,
>  	.framebuffer_lookup = i915_bo_framebuffer_lookup,  #if
> IS_ENABLED(CONFIG_DRM_FBDEV_EMULATION)
> +	.fbdev_bios_fb_takeover = i915_bo_fbdev_bios_fb_takeover,
>  	.fbdev_create = i915_bo_fbdev_create,
>  	.fbdev_destroy = i915_bo_fbdev_destroy,
>  	.fbdev_fill_info = i915_bo_fbdev_fill_info, diff --git
> a/drivers/gpu/drm/i915/i915_bo.h b/drivers/gpu/drm/i915/i915_bo.h index
> 39ba62696550e..57255d052dd9a 100644
> --- a/drivers/gpu/drm/i915/i915_bo.h
> +++ b/drivers/gpu/drm/i915/i915_bo.h
> @@ -4,12 +4,6 @@
>  #ifndef __I915_BO_H__
>  #define __I915_BO_H__
> 
> -#include <linux/types.h>
> -
> -struct drm_i915_private;
> -
> -bool i915_bo_fbdev_prefer_stolen(struct drm_i915_private *i915, unsigned int
> size);
> -
>  extern const struct intel_display_bo_interface i915_display_bo_interface;
> 
>  #endif /* __I915_BO_H__ */
> diff --git a/drivers/gpu/drm/i915/i915_initial_plane.c
> b/drivers/gpu/drm/i915/i915_initial_plane.c
> index 98858a78e46a3..d7792b65ec150 100644
> --- a/drivers/gpu/drm/i915/i915_initial_plane.c
> +++ b/drivers/gpu/drm/i915/i915_initial_plane.c
> @@ -12,7 +12,6 @@
>  #include "gem/i915_gem_lmem.h"
>  #include "gem/i915_gem_region.h"
> 
> -#include "i915_bo.h"
>  #include "i915_drv.h"
>  #include "i915_initial_plane.h"
> 
> @@ -102,19 +101,6 @@ initial_plane_vma(struct drm_i915_private *i915,
>  			mem->min_page_size);
>  	size -= base;
> 
> -	/*
> -	 * 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.
> -	 */
> -	if (IS_ENABLED(CONFIG_DRM_FBDEV_EMULATION) &&
> -	    IS_ENABLED(CONFIG_FRAMEBUFFER_CONSOLE) &&
> -	    mem == i915->mm.stolen_region &&
> -	    !i915_bo_fbdev_prefer_stolen(i915, size)) {
> -		drm_dbg_kms(&i915->drm, "Initial FB size exceeds half of stolen,
> discarding\n");
> -		return NULL;
> -	}
> -
>  	obj = i915_gem_object_create_region_at(mem, phys_base, size,
>  					       I915_BO_ALLOC_USER |
>  					       I915_BO_PREALLOC);
> diff --git a/drivers/gpu/drm/xe/display/xe_display_bo.c
> b/drivers/gpu/drm/xe/display/xe_display_bo.c
> index d78d893210c4f..188796ae85933 100644
> --- a/drivers/gpu/drm/xe/display/xe_display_bo.c
> +++ b/drivers/gpu/drm/xe/display/xe_display_bo.c
> @@ -9,6 +9,7 @@
>  #include "intel_fb.h"
>  #include "xe_bo.h"
>  #include "xe_display_bo.h"
> +#include "xe_migrate.h"
>  #include "xe_pxp.h"
>  #include "xe_ttm_stolen_mgr.h"
>  #include "xe_wa.h"
> @@ -120,7 +121,7 @@ static u32 xe_display_bo_fbdev_pitch_align(u32 stride)
>  	return ALIGN(stride, XE_PAGE_SIZE);
>  }
> 
> -bool xe_display_bo_fbdev_prefer_stolen(struct xe_device *xe, unsigned int size)
> +static bool xe_display_bo_fbdev_prefer_stolen(struct xe_device *xe,
> +unsigned int size)
>  {
>  	struct ttm_resource_manager *stolen;
> 
> @@ -152,6 +153,58 @@ bool xe_display_bo_fbdev_prefer_stolen(struct
> xe_device *xe, unsigned int size)
>  	return stolen->size >= (size * 2) >> PAGE_SHIFT;  }
> 
> +static struct drm_gem_object
> +*xe_display_bo_fbdev_bios_fb_takeover(struct drm_gem_object *obj) {
> +	struct xe_bo *orig_bo = gem_to_xe_bo(obj), *copy_bo;
> +	struct xe_device *xe = xe_bo_device(orig_bo);
> +	struct xe_validation_ctx ctx;
> +	struct drm_exec exec;
> +	int err;
> +
> +	if (IS_DGFX(xe) ||
> +	    xe_display_bo_fbdev_prefer_stolen(xe, xe_bo_size(orig_bo)))
> +		return obj;
> +
> +	copy_bo = xe_bo_create_pin_map_novm(xe, xe_device_get_root_tile(xe),
> xe_bo_size(orig_bo),
> +					    ttm_bo_type_kernel,
> +					    XE_BO_FLAG_FORCE_WC |
> XE_BO_FLAG_SYSTEM | XE_BO_FLAG_GGTT,
> +					    false);
> +	if (IS_ERR(copy_bo))
> +		return ERR_CAST(copy_bo);
> +
> +	xe_validation_guard(&ctx, &xe->val, &exec, (struct xe_val_flags) {}, err) {
> +		struct dma_fence *fence;
> +
> +		drm_exec_lock_obj(&exec, &orig_bo->ttm.base);
> +		drm_exec_retry_on_contention(&exec);
> +
> +		drm_exec_lock_obj(&exec, &copy_bo->ttm.base);
> +		drm_exec_retry_on_contention(&exec);
> +
> +		err = dma_resv_reserve_fences(orig_bo->ttm.base.resv, 1);
> +		if (err)
> +			break;
> +
> +		err = dma_resv_reserve_fences(copy_bo->ttm.base.resv, 1);
> +		if (err)
> +			break;
> +
> +		fence = xe_migrate_copy(xe_device_get_root_tile(xe)->migrate,
> orig_bo, copy_bo,
> +					orig_bo->ttm.resource, copy_bo-
> >ttm.resource, false);
> +		if (IS_ERR(fence)) {
> +			err = PTR_ERR(fence);
> +			break;
> +		}
> +
> +		dma_resv_add_fence(copy_bo->ttm.base.resv, fence,
> DMA_RESV_USAGE_KERNEL);
> +		dma_resv_add_fence(orig_bo->ttm.base.resv, fence,
> DMA_RESV_USAGE_BOOKKEEP);
> +		return &copy_bo->ttm.base;
> +	}
> +
> +	xe_bo_unpin_map_no_vm(copy_bo);
> +	return ERR_PTR(err);
> +}
> +
>  static struct drm_gem_object *xe_display_bo_fbdev_create(struct drm_device
> *drm, int size)  {
>  	struct xe_device *xe = to_xe_device(drm); @@ -214,6 +267,7 @@ const
> struct intel_display_bo_interface xe_display_bo_interface = {
>  	.framebuffer_fini = xe_display_bo_framebuffer_fini,
>  	.framebuffer_lookup = xe_display_bo_framebuffer_lookup,  #if
> IS_ENABLED(CONFIG_DRM_FBDEV_EMULATION)
> +	.fbdev_bios_fb_takeover = xe_display_bo_fbdev_bios_fb_takeover,
>  	.fbdev_create = xe_display_bo_fbdev_create,
>  	.fbdev_destroy = xe_display_bo_fbdev_destroy,
>  	.fbdev_fill_info = xe_display_bo_fbdev_fill_info, diff --git
> a/drivers/gpu/drm/xe/display/xe_display_bo.h
> b/drivers/gpu/drm/xe/display/xe_display_bo.h
> index c72056884ff41..6879c104b0b1f 100644
> --- a/drivers/gpu/drm/xe/display/xe_display_bo.h
> +++ b/drivers/gpu/drm/xe/display/xe_display_bo.h
> @@ -4,12 +4,6 @@
>  #ifndef __XE_DISPLAY_BO_H__
>  #define __XE_DISPLAY_BO_H__
> 
> -#include <linux/types.h>
> -
> -struct xe_device;
> -
> -bool xe_display_bo_fbdev_prefer_stolen(struct xe_device *xe, unsigned int size);
> -
>  extern const struct intel_display_bo_interface xe_display_bo_interface;
> 
>  #endif
> diff --git a/drivers/gpu/drm/xe/display/xe_initial_plane.c
> b/drivers/gpu/drm/xe/display/xe_initial_plane.c
> index 0f86b73036d03..8988c07e61934 100644
> --- a/drivers/gpu/drm/xe/display/xe_initial_plane.c
> +++ b/drivers/gpu/drm/xe/display/xe_initial_plane.c
> @@ -14,7 +14,6 @@
>  #include "intel_display_types.h"
> 
>  #include "xe_bo.h"
> -#include "xe_display_bo.h"
>  #include "xe_display_vma.h"
>  #include "xe_fb_pin.h"
>  #include "xe_ggtt.h"
> @@ -102,13 +101,6 @@ initial_plane_bo(struct xe_device *xe,
> 
>  		phys_base = base;
>  		flags |= XE_BO_FLAG_STOLEN;
> -
> -		if (IS_ENABLED(CONFIG_FRAMEBUFFER_CONSOLE) &&
> -		    IS_ENABLED(CONFIG_DRM_FBDEV_EMULATION) &&
> -		    !xe_display_bo_fbdev_prefer_stolen(xe, plane_config->size)) {
> -			drm_info(&xe->drm, "Initial FB size exceeds half of stolen,
> discarding\n");
> -			return NULL;
> -		}
>  	}
> 
>  	bo = xe_bo_create_pin_map_at_novm(xe, tile0, size, phys_base, diff --git
> a/include/drm/intel/display_parent_interface.h
> b/include/drm/intel/display_parent_interface.h
> index de395df9ca301..b218f8ecbe22a 100644
> --- a/include/drm/intel/display_parent_interface.h
> +++ b/include/drm/intel/display_parent_interface.h
> @@ -58,6 +58,7 @@ struct intel_display_bo_interface {
>  						     struct drm_file *filp,
>  						     const struct
> drm_mode_fb_cmd2 *user_mode_cmd);  #if
> IS_ENABLED(CONFIG_DRM_FBDEV_EMULATION)
> +	struct drm_gem_object *(*fbdev_bios_fb_takeover)(struct
> drm_gem_object
> +*obj);
>  	struct drm_gem_object *(*fbdev_create)(struct drm_device *drm, int size);
>  	void (*fbdev_destroy)(struct drm_gem_object *obj);
>  	int (*fbdev_fill_info)(struct drm_gem_object *obj, struct fb_info *info, struct
> i915_vma *vma);
> --
> 2.53.0