[PATCH] drm/xe/fbdev: Limit the usage of stolen for LNL+

[Lucas De Marchi]

On Thu, Jul 11, 2024 at 10:43:39AM GMT, Uma Shankar wrote:
>As per recommendation in the workarounds:
>WA_14021987551, Wa_16023588340:
>
>There is an issue with accessing Stolen memory pages due a
>hardware limitation. Limit the usage of stolen memory for
>fbdev for LNL+. Don't use BIOS FB from stolen on LNL+ and
>assign the same from system memory.
>
>Signed-off-by: Uma Shankar <uma.shankar at intel.com>
>---
> drivers/gpu/drm/xe/display/intel_fbdev_fb.c   | 10 +++++++++-
> drivers/gpu/drm/xe/display/xe_plane_initial.c | 10 ++++++++++
> 2 files changed, 19 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/xe/display/intel_fbdev_fb.c b/drivers/gpu/drm/xe/display/intel_fbdev_fb.c
>index 816ad13821a8..8fda8745ce0a 100644
>--- a/drivers/gpu/drm/xe/display/intel_fbdev_fb.c
>+++ b/drivers/gpu/drm/xe/display/intel_fbdev_fb.c
>@@ -37,7 +37,14 @@ struct intel_framebuffer *intel_fbdev_fb_alloc(struct drm_fb_helper *helper,
> 	size = PAGE_ALIGN(size);
> 	obj = ERR_PTR(-ENODEV);
>
>-	if (!IS_DGFX(xe)) {
>+	/*
>+	 * WA_14021987551, Wa_16023588340:

not the proper way to handle WAs in xe. Please use XE_WA()


>+	 * There is an issue with accessing Stolen memory pages
>+	 * due a hardware limitation. Limit the usage of stolen
>+	 * memory for fbdev for LNL+. Don't use BIOS FB from
>+	 * stolen on LNL+ and assign the same from system memory

I wonder if we can't simply set to 0 the available stolen space after the
places that really need it already had their allocation done.

>+	 */
>+	if (!IS_DGFX(xe) && (DISPLAY_VER(xe) < 20)) {

extra parenthesis not needed and I think the rule to be added in
xe_wa_oob.rules would be about GRAPHICS_VERSION(2004) or
PLATFORM(LUNARLAKE) to avoid this propagating to future platforms.

> 		obj = xe_bo_create_pin_map(xe, xe_device_get_root_tile(xe),
> 					   NULL, size,
> 					   ttm_bo_type_kernel, XE_BO_FLAG_SCANOUT |
>@@ -48,6 +55,7 @@ struct intel_framebuffer *intel_fbdev_fb_alloc(struct drm_fb_helper *helper,
> 		else
> 			drm_info(&xe->drm, "Allocated fbdev into stolen failed: %li\n", PTR_ERR(obj));
> 	}
>+
> 	if (IS_ERR(obj)) {
> 		obj = xe_bo_create_pin_map(xe, xe_device_get_root_tile(xe), NULL, size,
> 					   ttm_bo_type_kernel, XE_BO_FLAG_SCANOUT |
>diff --git a/drivers/gpu/drm/xe/display/xe_plane_initial.c b/drivers/gpu/drm/xe/display/xe_plane_initial.c
>index 5eccd6abb3ef..80dd6b64c921 100644
>--- a/drivers/gpu/drm/xe/display/xe_plane_initial.c
>+++ b/drivers/gpu/drm/xe/display/xe_plane_initial.c
>@@ -104,6 +104,16 @@ initial_plane_bo(struct xe_device *xe,
> 		phys_base = base;
> 		flags |= XE_BO_FLAG_STOLEN;
>
>+		/*
>+		 * WA_14021987551, Wa_16023588340:
>+		 * There is an issue with accessing Stolen memory pages
>+		 * due a hardware limitation. Limit the usage of stolen
>+		 * memory for fbdev for LNL+. Don't use BIOS FB from
>+		 * stolen on LNL+ and assign the same from system memory
>+		 */
>+		if (DISPLAY_VER(xe) >= 20)
>+			return NULL;

same as above

Lucas De Marchi

>+
> 		/*
> 		 * 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
>-- 
>2.42.0
>