[Intel-gfx] [PATCH 1/5] drm/i915/fbc: Remove ancient 16k plane stride limit

[Matt Roper]

On Thu, Sep 14, 2023 at 02:38:50PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The 16k max plane stride limit seems to be originally from
> i965gm, and no limit explicit limit has been specified since (g4x+).

There are maximum limits specified on the PLANE_STRIDE register pages
(bspec 7667, 50416, 69877).

display version 9 - 10:   max 8k pixels and 32k bytes
display version 11 - 12:  max 8k pixels
display version 13 - 20:  max 128k bytes


Matt

> So let's assume the max plane stride itself is a suitable limit
> also for the more recent FBC hardware.
> 
> In fact even for i965gm the max X-tiled stride is also 16k so
> technically we don't need the check there either, but let's
> keep it there anyway since it's explicitly mentioned in the
> spec. Gen2/3 have more strict limits checked separately.
> 
> Cc: Swati Sharma <swati2.sharma at intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_fbc.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
> index 817e5784660b..1b3358a0fbfb 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> @@ -866,7 +866,8 @@ static bool stride_is_valid(const struct intel_plane_state *plane_state)
>  	if (DISPLAY_VER(i915) == 2 || DISPLAY_VER(i915) == 3)
>  		return stride == 4096 || stride == 8192;
>  
> -	if (DISPLAY_VER(i915) == 4 && !IS_G4X(i915) && stride < 2048)
> +	if (DISPLAY_VER(i915) == 4 && !IS_G4X(i915) &&
> +	    (stride < 2048 || stride > 16384))
>  		return false;
>  
>  	/* Display WA #1105: skl,bxt,kbl,cfl,glk */
> @@ -874,9 +875,6 @@ static bool stride_is_valid(const struct intel_plane_state *plane_state)
>  	    fb->modifier == DRM_FORMAT_MOD_LINEAR && stride & 511)
>  		return false;
>  
> -	if (stride > 16384)
> -		return false;
> -
>  	return true;
>  }
>  
> -- 
> 2.41.0
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation