[Intel-gfx] [PATCH] drm/i915/edp: Read link status after exit PSR

[Lee, Shawn C]

-----Original Message-----
From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com] 
Sent: Thursday, April 27, 2017 10:39 PM
To: Lee, Shawn C <shawn.c.lee at intel.com>
Cc: intel-gfx at lists.freedesktop.org; Chiou, Cooper <cooper.chiou at intel.com>; Bride, Jim <jim.bride at intel.com>; Nikula, Jani <jani.nikula at intel.com>; Vivi, Rodrigo <rodrigo.vivi at intel.com>; Lin, Ryan <ryan.lin at intel.com>
Subject: Re: [Intel-gfx] [PATCH] drm/i915/edp: Read link status after exit PSR

On Thu, Apr 27, 2017 at 10:35:22PM +0800, Lee, Shawn C wrote:
> From: "Lee, Shawn C" <shawn.c.lee at 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?

When read DPCD link status register, eDP can't at link train stage (after PSR exit). 
TCON report EQ not done then will cause link re-training and display flicker. 
So we read SRD_STATUS to make sure source did not send TP1, TP2, TP3 or idle
pattern to sink side for link training.

> 
> 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 at intel.com>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Jim Bride <jim.bride at intel.com>
> Cc: Ryan Lin <ryan.lin at intel.com>
> 
> Signed-off-by: Shawn Lee <shawn.c.lee at 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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> Intel-gfx at lists.freedesktop.org
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--
Ville Syrjälä
Intel OTC