[Intel-gfx] [PATCH] drm/i915/glk: Don't allow 12 bpc when htotal is too big

[Sharma, Shashank]

Regards

Shashank


On 4/24/2017 4:17 PM, Ander Conselvan de Oliveira wrote:
> Display workaround #1139 for Geminilake instructs us to restrict HDMI
> to 8 bpc when htotal is greater than 5460. Otherwise, the pipe is unable
> to generate a proper signal and is left in a state where corruption is
> seen with other modes.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100440
> Cc: Shashank Sharma <shashank.sharma at intel.com>
> Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at intel.com>
> ---
>   drivers/gpu/drm/i915/intel_hdmi.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index 6efc3cb..52f0b2d 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1327,6 +1327,11 @@ static bool hdmi_12bpc_possible(struct intel_crtc_state *crtc_state)
>   			return false;
>   	}
>   
> +	/* Display Wa #1139 */
> +	if (IS_GLK_REVID(dev_priv, 0, GLK_REVID_A1) &&
> +	    crtc_state->base.adjusted_mode.htotal > 5460)
Small inputs:
- We might wanna extend this for CNL too, as the WAR is valid for it 
too. I am not sure it should be this same patch or not.
- We need to modify this check not to affect the YCBCR 420 modes, as 
there won't be any change between the timings of a YCBCR mode and a
   normal mode (apart from a flag), but htotal should be valid in YCBCR 
420 case. But I can handle this part while sending second patch set of
   YCBCR 420 handling.
- Also, should we reject 12BPC totally, or just clamp htotal to max 
possible (5460) and go ahead? Ville ?

In any case, please feel free to use:
Reviewed-by: Shashank Sharma <shashank.sharma at intel.com>
> +		return false;
> +
>   	return true;
>   }
>