Re: [PATCH v1 1/2] drm/i915/display: use PAGE_SIZE macro for FBC cfb alloc

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

On Wed, Jan 10, 2024 at 01:00:08PM +0200, Vinod Govindapillai wrote:
> FBC compressed frame buffer size need to be PAGE_SIZE aligned
> and the corresponding the drm_gem functions check the object
> size alignment using PAGE_SIZE macro. Use the PAGE_SIZE macro
> in the cfb alloc as well instead of the magic number.
> 
> Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_fbc.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
> index f17a1afb4929..9b9c8715d664 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> @@ -764,13 +764,15 @@ static int find_compression_limit(struct intel_fbc *fbc,
>  
>  	/* Try to over-allocate to reduce reallocations and fragmentation. */
>  	ret = i915_gem_stolen_insert_node_in_range(i915, &fbc->compressed_fb,
> -						   size <<= 1, 4096, 0, end);
> +						   size <<= 1, PAGE_SIZE, 0,
> +						   end);
>  	if (ret == 0)
>  		return limit;
>  
>  	for (; limit <= intel_fbc_max_limit(i915); limit <<= 1) {
>  		ret = i915_gem_stolen_insert_node_in_range(i915, &fbc->compressed_fb,
> -							   size >>= 1, 4096, 0, end);
> +							   size >>= 1, PAGE_SIZE, 0,
> +							   end);

PAGE_SIZE is 4k so I can't see this doing anything at all.

The correct fix is probably either:
- fix the xe gem code to always page align the size
- page align it in xe's i915_gem_stolen_insert_node_in_range()

>  		if (ret == 0)
>  			return limit;
>  	}
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel