[Intel-gfx] [PATCH 1/2] drm/i915: Fix g4x+ sprite dotclock limit for upscaling

[Jani Nikula]

On Thu, 06 Feb 2020, Ville Syrjala <ville.syrjala at linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> Even if we're not doing downscaling we should account for
> some of the extra dotclock limitations for g4x+ sprites. In
> particular we must never exceed the 90% rule, and with RGB
> that limits actually drops to 80%.
>
> So instead of bailing out when upscaling let's clamp the
> scaling factor appropriately and go through the rest of
> calculation normally. By luck we already did the full
> calculations for the 1:1 case.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_sprite.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_sprite.c b/drivers/gpu/drm/i915/display/intel_sprite.c
> index 7abeefe8dce5..6e2e22d9bbaa 100644
> --- a/drivers/gpu/drm/i915/display/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/display/intel_sprite.c
> @@ -1611,8 +1611,7 @@ static int g4x_sprite_min_cdclk(const struct intel_crtc_state *crtc_state,
>  	hscale = drm_rect_calc_hscale(&plane_state->uapi.src,
>  				      &plane_state->uapi.dst,
>  				      0, INT_MAX);
> -	if (hscale < 0x10000)
> -		return pixel_rate;
> +	hscale = max(hscale, 0x10000u);

It bugs me that drm_rect seems to be used for both integer and 16.16
fixed point and whatnot.

It also gives me an uneasy feeling that hscale is uint while
drm_rect_calc_hscale() may return -ERANGE... but I guess shouldn't
happen.

All in all,

Reviewed-by: Jani Nikula <jani.nikula at intel.com>


>  
>  	/* Decimation steps at 2x,4x,8x,16x */
>  	decimate = ilog2(hscale >> 16);

-- 
Jani Nikula, Intel Open Source Graphics Center