Re: [PATCH v2] drm/{i915,xe}/fbdev: add intel_fbdev_fb_pitch_align()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Oct 22, 2025 at 07:10:54PM +0300, Jani Nikula wrote:
> For reasons still unknown, xe appears to require a stride alignment of
> XE_PAGE_SIZE, and using 64 leads to sporadic failures. Go back to having
> separate stride alignment for i915 and xe, until the issue is root
> caused.
> 
> v2: Add FIXME comment, reference issue with Link (Ville)
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Jouni Högander <jouni.hogander@intel.com>
> Cc: Maarten Lankhorst <maarten@lankhorst.se>
> Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6220
> Fixes: 4a36b339a14a ("drm/xe/fbdev: use the same 64-byte stride alignment as i915")
> Link: https://lore.kernel.org/r/ae51d1e224048bdc87bf7a56d8f5ebd0fbb6a383.1756931441.git.jani.nikula@intel.com
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_fbdev.c    |  2 +-
>  drivers/gpu/drm/i915/display/intel_fbdev_fb.c |  5 +++++
>  drivers/gpu/drm/i915/display/intel_fbdev_fb.h |  3 +++
>  drivers/gpu/drm/xe/display/intel_fbdev_fb.c   | 11 +++++++++++
>  4 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
> index 51d3d87caf43..d5c001761aa0 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> @@ -218,7 +218,7 @@ static void intel_fbdev_fill_mode_cmd(struct drm_fb_helper_surface_size *sizes,
>  	mode_cmd->width = sizes->surface_width;
>  	mode_cmd->height = sizes->surface_height;
>  
> -	mode_cmd->pitches[0] = ALIGN(mode_cmd->width * DIV_ROUND_UP(sizes->surface_bpp, 8), 64);
> +	mode_cmd->pitches[0] = intel_fbdev_fb_pitch_align(mode_cmd->width * DIV_ROUND_UP(sizes->surface_bpp, 8));
>  	mode_cmd->pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp,
>  							   sizes->surface_depth);
>  	mode_cmd->modifier[0] = DRM_FORMAT_MOD_LINEAR;
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev_fb.c b/drivers/gpu/drm/i915/display/intel_fbdev_fb.c
> index 56b145841473..0838fdd37254 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev_fb.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev_fb.c
> @@ -10,6 +10,11 @@
>  #include "i915_drv.h"
>  #include "intel_fbdev_fb.h"
>  
> +u32 intel_fbdev_fb_pitch_align(u32 stride)
> +{
> +	return ALIGN(stride, 64);
> +}
> +
>  struct drm_gem_object *intel_fbdev_fb_bo_create(struct drm_device *drm, int size)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(drm);
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev_fb.h b/drivers/gpu/drm/i915/display/intel_fbdev_fb.h
> index 1fa44ed28543..fd0b3775dc1f 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev_fb.h
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev_fb.h
> @@ -6,12 +6,15 @@
>  #ifndef __INTEL_FBDEV_FB_H__
>  #define __INTEL_FBDEV_FB_H__
>  
> +#include <linux/types.h>
> +
>  struct drm_device;
>  struct drm_gem_object;
>  struct drm_mode_fb_cmd2;
>  struct fb_info;
>  struct i915_vma;
>  
> +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,
> diff --git a/drivers/gpu/drm/xe/display/intel_fbdev_fb.c b/drivers/gpu/drm/xe/display/intel_fbdev_fb.c
> index af72f7305e5a..7ad76022cb14 100644
> --- a/drivers/gpu/drm/xe/display/intel_fbdev_fb.c
> +++ b/drivers/gpu/drm/xe/display/intel_fbdev_fb.c
> @@ -12,6 +12,17 @@
>  
>  #include <generated/xe_device_wa_oob.h>
>  
> +/*
> + * FIXME: There shouldn't be any reason to have XE_PAGE_SIZE stride
> + * alignment. The same 64 as i915 uses should be fine, and we shouldn't need to
> + * have driver specific values. However, dropping the stride alignment to 64
> + * leads to underflowing the bo pin count in the atomic cleanup work.
> + */
> +u32 intel_fbdev_fb_pitch_align(u32 stride)
> +{
> +	return ALIGN(stride, XE_PAGE_SIZE);
> +}
> +
>  struct drm_gem_object *intel_fbdev_fb_bo_create(struct drm_device *drm, int size)
>  {
>  	struct xe_device *xe = to_xe_device(drm);
> -- 
> 2.47.3

-- 
Ville Syrjälä
Intel