Re: [PATCH] drm/i915/gen9: Disable FBC on planes which have an unsupported config.

[Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>]

On 29.1.2019 14.57, Gwan-gyeong Mun wrote:
> Enabling FBC on a plane which has a combination of a 180-degree rotation
> with having a Height that isn't divisible by 4 causes FIFO underrun,
> so disable FBC on such a config.
> 
> Testcase: igt/kms_rotation_crc/multiplane-rotation-cropping-top
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105604
> 
> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> ---
>   drivers/gpu/drm/i915/intel_fbc.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
> index ccd5e110a19c..de4b5781922c 100644
> --- a/drivers/gpu/drm/i915/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/intel_fbc.c
> @@ -793,6 +793,18 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
>   		return false;
>   	}
>   
> +	/*
> +	 * Work around a problem on GEN9 HW, where enabling FBC on a plane
> +	 * which has a combination of a 180-degree rotation with having a Height
> +	 * that isn't divisible by 4 causes FIFO underrun.
> +	 */
> +	if (IS_GEN(dev_priv, 9) &&
> +	    (cache->plane.rotation == DRM_MODE_ROTATE_180) &&
> +	    (fbc->state_cache.plane.src_h & 3)) {
> +		fbc->no_fbc_reason = "plane has a combination of a 180-degree rotation with a misaligned Height";
> +		return false;
> +	}
> +
>   	return true;
>   }
>   
> 

I see there extra parenthesis but it's in line with style used just 
above this piece of code so I guess it's ok.

Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
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