Re: [PATCH] drm/i915/edp: Read link status after exit PSR

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Apr 27, 2017 at 10:35:22PM +0800, Lee, Shawn C wrote:
> From: "Lee, Shawn C" <shawn.c.lee@intel.com>
> 
> Display driver read DPCD register 0x202, 0x203 and 0x204 to identify
> eDP sink status. If PSR exit is ongoing at eDP sink, and eDP source
> read these registers at the same time. Panel will report EQ & symbol
> lock not done. It will cause panel display flicking.
> So driver have to make sure PSR already exit before read link status.

And what exactly guarantees that it will exit PSR eventually?

> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99639
> TEST=Reboot DUT and no flicking on local display at login screen
> 
> Cc: Cooper Chiou <cooper.chiou@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Jim Bride <jim.bride@intel.com>
> Cc: Ryan Lin <ryan.lin@intel.com>
> 
> Signed-off-by: Shawn Lee <shawn.c.lee@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c |   34 +++++++++++++++++++++++++++++-----
>  1 file changed, 29 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 08834f74d396..cc431337b2dc 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4252,19 +4252,35 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
>  }
>  
>  static void
> +intel_edp_wait_PSR_exit(struct intel_dp *intel_dp)
> +{
> +	struct drm_device *dev = intel_dp_to_dev(intel_dp);
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	u32 srd_status, count = 100;
> +
> +	while (count--) {
> +		srd_status = I915_READ(EDP_PSR_STATUS_CTL);
> +
> +		if ((srd_status & EDP_PSR_STATUS_SENDING_TP1) ||
> +		    (srd_status & EDP_PSR_STATUS_SENDING_TP2_TP3) ||
> +		    (srd_status & EDP_PSR_STATUS_SENDING_IDLE) ||
> +		    (srd_status & EDP_PSR_STATUS_AUX_SENDING)) {
> +			usleep_range(100, 150);
> +		} else
> +			return;
> +	}
> +}
> +
> +static void
>  intel_dp_check_link_status(struct intel_dp *intel_dp)
>  {
>  	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
>  	struct drm_device *dev = intel_dp_to_dev(intel_dp);
> +	struct drm_i915_private *dev_priv = dev->dev_private;
>  	u8 link_status[DP_LINK_STATUS_SIZE];
>  
>  	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
>  
> -	if (!intel_dp_get_link_status(intel_dp, link_status)) {
> -		DRM_ERROR("Failed to get link status\n");
> -		return;
> -	}
> -
>  	if (!intel_encoder->base.crtc)
>  		return;
>  
> @@ -4278,6 +4294,14 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
>  	if (!intel_dp_link_params_valid(intel_dp))
>  		return;
>  
> +	if (is_edp(intel_dp) && dev_priv->psr.enabled)
> +		intel_edp_wait_PSR_exit(intel_dp);
> +
> +	if (!intel_dp_get_link_status(intel_dp, link_status)) {
> +		DRM_ERROR("Failed to get link status\n");
> +		return;
> +	}
> +
>  	/* Retrain if Channel EQ or CR not ok */
>  	if (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count)) {
>  		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
> -- 
> 1.7.9.5
> 
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-- 
Ville Syrjälä
Intel OTC
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