Re: [PATCH] drm/i915: Avoid TP3 on CHV

From: Jani Nikula <jani.nikula@linux.intel.com>
To: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>,
	ville.syrjala@linux.intel.com, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: Avoid TP3 on CHV
Date: Wed, 19 Aug 2015 11:20:04 +0300	[thread overview]
Message-ID: <87io8bd70r.fsf@intel.com> (raw)
In-Reply-To: <1439892037-6269-1-git-send-email-sivakumar.thulasimani@intel.com>

On Tue, 18 Aug 2015, Sivakumar Thulasimani <sivakumar.thulasimani@intel.com> wrote:
> From: "Thulasimani,Sivakumar" <sivakumar.thulasimani@intel.com>
>
> This patch removes TP3 support on CHV since there is no support
> for HBR2 on this platform.
>
> v2: rename the function to indicate it checks source rates (Jani)
> v3: update comment to indicate TP3 dependancy on HBR2 supported
>     hardware (Jani)
>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>

Pushed first three patches in the series to drm-intel-fixes, thanks for
the patches and review. (The last patch is skl specific, I'll pick it up
for v4.3 in drm-intel-next-fixes after a backmerge.)

BR,
Jani.

> ---
>  drivers/gpu/drm/i915/intel_dp.c |   31 +++++++++++++++++++++++--------
>  1 file changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 475d8cb..051614a 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1207,6 +1207,20 @@ intel_dp_sink_rates(struct intel_dp *intel_dp, const int **sink_rates)
>  	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
>  }
>  
> +static bool intel_dp_source_supports_hbr2(struct drm_device *dev)
> +{
> +	/* WaDisableHBR2:skl */
> +	if (IS_SKYLAKE(dev) && INTEL_REVID(dev) <= SKL_REVID_B0)
> +		return false;
> +
> +	if ((IS_HASWELL(dev) && !IS_HSW_ULX(dev)) || IS_BROADWELL(dev) ||
> +	    (INTEL_INFO(dev)->gen >= 9))
> +		return true;
> +	else
> +		return false;
> +}
> +
> +
>  static int
>  intel_dp_source_rates(struct drm_device *dev, const int **source_rates)
>  {
> @@ -1220,12 +1234,8 @@ intel_dp_source_rates(struct drm_device *dev, const int **source_rates)
>  
>  	*source_rates = default_rates;
>  
> -	/* WaDisableHBR2:skl */
> -	if (IS_SKYLAKE(dev) && INTEL_REVID(dev) <= SKL_REVID_B0)
> -		return (DP_LINK_BW_2_7 >> 3) + 1;
> -
> -	if ((IS_HASWELL(dev) && !IS_HSW_ULX(dev)) || IS_BROADWELL(dev) ||
> -	    (INTEL_INFO(dev)->gen >= 9))
> +	/* This depends on the fact that 5.4 is last value in the array */
> +	if (intel_dp_source_supports_hbr2(dev))
>  		return (DP_LINK_BW_5_4 >> 3) + 1;
>  	else
>  		return (DP_LINK_BW_2_7 >> 3) + 1;
> @@ -3923,10 +3933,15 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
>  		}
>  	}
>  
> -	/* Training Pattern 3 support, both source and sink */
> +	/* Training Pattern 3 support, Intel platforms that support HBR2 alone
> +	 * have support for TP3 hence that check is used along with dpcd check
> +	 * to ensure TP3 can be enabled.
> +	 * SKL < B0: due it's WaDisableHBR2 is the only exception where TP3 is
> +	 * supported but still not enabled.
> +	 */
>  	if (intel_dp->dpcd[DP_DPCD_REV] >= 0x12 &&
>  	    intel_dp->dpcd[DP_MAX_LANE_COUNT] & DP_TPS3_SUPPORTED &&
> -	    (IS_HASWELL(dev_priv) || INTEL_INFO(dev_priv)->gen >= 8)) {
> +	    intel_dp_source_supports_hbr2(dev)) {
>  		intel_dp->use_tps3 = true;
>  		DRM_DEBUG_KMS("Displayport TPS3 supported\n");
>  	} else
> -- 
> 1.7.9.5
>

-- 
Jani Nikula, Intel Open Source Technology Center
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