Re: [PATCH v2 08/11] drm/i915/psr: Check if source supports sink specific SU granularity

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

On Thu, 2018-11-29 at 18:25 -0800, José Roberto de Souza wrote:
> According to eDP spec, sink can required specific selective update
> granularity that source must comply.
> Here caching the value if required and checking if source supports
> it.
> 
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h  |  1 +
>  drivers/gpu/drm/i915/intel_psr.c | 21 ++++++++++++++++++++-
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h
> b/drivers/gpu/drm/i915/i915_drv.h
> index 43ac6873a2bb..0727d8051dd3 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -507,6 +507,7 @@ struct i915_psr {
>  	ktime_t last_exit;
>  	bool sink_not_reliable;
>  	bool irq_aux_error;
> +	u16 su_x_granularity;
>  };
>  
>  enum intel_pch {
> diff --git a/drivers/gpu/drm/i915/intel_psr.c
> b/drivers/gpu/drm/i915/intel_psr.c
> index 282ff1bc68a7..f9eccaac850a 100644
> --- a/drivers/gpu/drm/i915/intel_psr.c
> +++ b/drivers/gpu/drm/i915/intel_psr.c
> @@ -261,6 +261,23 @@ static u8 intel_dp_get_sink_sync_latency(struct
> intel_dp *intel_dp)
>  	return val;
>  }
>  
> +static u16 intel_dp_get_su_x_granulartiy(struct intel_dp *intel_dp)
> +{
> +	u16 val;
> +	ssize_t r;
> +
> +	if (!(intel_dp->psr_dpcd[1] & DP_PSR2_SU_GRANULARITY_REQUIRED))
> {
> +		/* Returning the default X granularity */
> +		return 4;
> +	}
nit: Braces not needed, you could move the comment a line above.

A value of 0 in this DPCD indicates there is no granularity
requirement, why assume 4? 

> +
> +	r = drm_dp_dpcd_read(&intel_dp->aux, DP_PSR2_SU_X_GRANULARITY,
> &val, 2);
> +	if (r != 2)
> +		DRM_WARN("Unable to read DP_PSR2_SU_X_GRANULARITY\n");
Please change this to the warning level that we use elsewhere for aux
failures.

If I'm reading the spec correctly, a value of 0 in this DPCD means the
sink expects a granularity of 4, so returning 0 would be incorrect.

> +
> +	return val;
Assume the default value of 4 if aux read fails (after printing an
error)

> +}
> +
>  void intel_psr_init_dpcd(struct intel_dp *intel_dp)
>  {
>  	struct drm_i915_private *dev_priv =
> @@ -315,6 +332,8 @@ void intel_psr_init_dpcd(struct intel_dp
> *intel_dp)
>  		if (dev_priv->psr.sink_psr2_support) {
>  			dev_priv->psr.colorimetry_support =
>  				intel_dp_get_colorimetry_status(intel_d
> p);
> +			dev_priv->psr.su_x_granularity =
> +				intel_dp_get_su_x_granulartiy(intel_dp)
> ;
>  		}
>  	}
>  }
> @@ -546,7 +565,7 @@ static bool intel_psr2_config_valid(struct
> intel_dp *intel_dp,
>  	 * at each 4 lines with height of 4 lines, what eDP states
>  	 * that sink should support.
>  	 */
> -	if (crtc_hdisplay % 4) {
> +	if (crtc_hdisplay % dev_priv->psr.su_x_granularity) {
>  		DRM_DEBUG_KMS("PSR2 not enabled, default SU granularity
> not match\n");
>  		return false;
>  	}

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