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

From: Ander Conselvan De Oliveira <conselvan2@gmail.com>
To: intel-gfx@lists.freedesktop.org,
	Shashank Sharma <shashank.sharma@intel.com>,
	Jani Nikula <jani.nikula@intel.com>
Subject: Re: [PATCH] drm/i915/glk: Don't allow 12 bpc when htotal is too big
Date: Mon, 24 Apr 2017 13:56:30 +0300	[thread overview]
Message-ID: <1493031390.4965.11.camel@gmail.com> (raw)
In-Reply-To: <20170424104718.26448-1-ander.conselvan.de.oliveira@intel.com>

On Mon, 2017-04-24 at 13:47 +0300, 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@intel.com>
> Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>

Perhaps this should have

Fixes: 14292b7ff86f ("drm/i915: allow HDMI 2.0 clock rates")

since it is only after that patch that the issue would be exposed, even though
is not the cause for it. Jani?

Ander

> ---
>  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)
> +		return false;
> +
>  	return true;
>  }
>  
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