Re: [PATCH 11/14] drm/i915: Fallback to lower link rate and lane count during link training

[Manasi Navare <manasi.d.navare@intel.com>]

On Fri, Sep 02, 2016 at 03:49:02PM +0300, David Weinehall wrote:
> On Thu, Sep 01, 2016 at 03:08:16PM -0700, Manasi Navare wrote:
> > According to the DisplayPort Spec, in case of Clock Recovery failure
> > the link training sequence should fall back to the lower link rate
> > followed by lower lane count until CR succeeds.
> > On CR success, the sequence proceeds with Channel EQ.
> > In case of Channel EQ failures, it should fallback to
> > lower link rate and lane count and start the CR phase again.
> > 
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_ddi.c              | 109 +++++++++++++++++++++++---
> >  drivers/gpu/drm/i915/intel_dp_link_training.c |  12 ++-
> >  drivers/gpu/drm/i915/intel_drv.h              |   4 +-
> >  3 files changed, 110 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > index 67a6a0b..78d6687 100644
> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > @@ -1634,29 +1634,50 @@ void intel_ddi_clk_select(struct intel_encoder *encoder,
> >  	}
> >  }
> >  
> > -static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> > +static void intel_ddi_pre_enable_edp(struct intel_encoder *encoder,
> >  				    int link_rate, uint32_t lane_count,
> > -				    struct intel_shared_dpll *pll,
> > -				    bool link_mst)
> > +				    struct intel_shared_dpll *pll)
> >  {
> >  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> >  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> >  	enum port port = intel_ddi_get_encoder_port(encoder);
> >  
> >  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
> > -				 link_mst);
> > -	if (encoder->type == INTEL_OUTPUT_EDP)
> > -		intel_edp_panel_on(intel_dp);
> > +				 false);
> > +
> > +	intel_edp_panel_on(intel_dp);
> >  
> >  	intel_ddi_clk_select(encoder, pll);
> >  	intel_prepare_dp_ddi_buffers(encoder);
> >  	intel_ddi_init_dp_buf_reg(encoder);
> >  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> >  	intel_dp_start_link_train(intel_dp);
> > -	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
> > +	if (port != PORT_A || INTEL_INFO(dev_priv)->gen >= 9)
> >  		intel_dp_stop_link_train(intel_dp);
> >  }
> >  
> > +static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> > +				    int link_rate, uint32_t lane_count,
> > +				    struct intel_shared_dpll *pll,
> > +				    bool link_mst)
> > +{
> > +	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> > +	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> > +	struct intel_shared_dpll_config tmp_pll_config;
> > +
> > +	/* Disable the PLL and obtain the PLL for Link Training
> > +	 * that starts with highest link rate and lane count.
> > +	 */
> > +	tmp_pll_config = pll->config;
> > +	pll->funcs.disable(dev_priv, pll);
> > +	pll->config.crtc_mask = 0;
> > +
> > +	/* If Link Training fails, send a uevent to generate a hotplug */
> > +	if (!(intel_ddi_link_train(intel_dp, link_rate, lane_count, link_mst)))
> > +		drm_kms_helper_hotplug_event(encoder->base.dev);
> > +	pll->config = tmp_pll_config;
> > +}
> > +
> >  static void intel_ddi_pre_enable_hdmi(struct intel_encoder *encoder,
> >  				      bool has_hdmi_sink,
> >  				      struct drm_display_mode *adjusted_mode,
> > @@ -1690,20 +1711,26 @@ static void intel_ddi_pre_enable(struct intel_encoder *intel_encoder,
> >  	struct intel_crtc *crtc = to_intel_crtc(encoder->crtc);
> >  	int type = intel_encoder->type;
> >  
> > -	if (type == INTEL_OUTPUT_DP || type == INTEL_OUTPUT_EDP) {
> > +	if (type == INTEL_OUTPUT_EDP)
> > +		intel_ddi_pre_enable_edp(intel_encoder,
> > +					crtc->config->port_clock,
> > +					crtc->config->lane_count,
> > +					crtc->config->shared_dpll);
> > +
> > +	if (type == INTEL_OUTPUT_DP)
> >  		intel_ddi_pre_enable_dp(intel_encoder,
> >  					crtc->config->port_clock,
> >  					crtc->config->lane_count,
> >  					crtc->config->shared_dpll,
> >  					intel_crtc_has_type(crtc->config,
> >  							    INTEL_OUTPUT_DP_MST));
> > -	}
> > -	if (type == INTEL_OUTPUT_HDMI) {
> > +
> > +	if (type == INTEL_OUTPUT_HDMI)
> >  		intel_ddi_pre_enable_hdmi(intel_encoder,
> >  					  crtc->config->has_hdmi_sink,
> >  					  &crtc->config->base.adjusted_mode,
> >  					  crtc->config->shared_dpll);
> > -	}
> > +
> >  }
> >  
> >  static void intel_ddi_post_disable(struct intel_encoder *intel_encoder,
> > @@ -2431,6 +2458,66 @@ intel_ddi_get_link_dpll(struct intel_dp *intel_dp, int clock)
> >  	return pll;
> >  }
> >  
> > +bool
> > +intel_ddi_link_train(struct intel_dp *intel_dp, int max_link_rate,
> > +		    uint8_t max_lane_count, bool link_mst)
> > +{
> > +	struct intel_connector *connector = intel_dp->attached_connector;
> > +	struct intel_encoder *encoder = connector->encoder;
> > +	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> > +	struct intel_shared_dpll *pll;
> > +	struct intel_shared_dpll_config tmp_pll_config;
> > +	int link_rate;
> > +	uint8_t lane_count;
> > +	bool link_rate_not_found = true;
> > +	bool ret = false;
> > +
> > +	for (lane_count = max_lane_count; lane_count > 0; lane_count >>= 1) {
> > +
> > +		link_rate = max_link_rate;
> > +		while (link_rate_not_found) {
> > +			pll = intel_ddi_get_link_dpll(intel_dp, link_rate);
> > +			if (pll == NULL) {
> > +				DRM_ERROR("Could not find DPLL for link "
> > +					  "training.\n");
> > +				return false;
> > +			}
> > +			tmp_pll_config = pll->config;
> > +			pll->funcs.enable(dev_priv, pll);
> > +
> > +			intel_dp_set_link_params(intel_dp, link_rate,
> > +						 lane_count, link_mst);
> > +
> > +			intel_ddi_clk_select(encoder, pll);
> > +			intel_prepare_dp_ddi_buffers(encoder);
> > +			intel_ddi_init_dp_buf_reg(encoder);
> 
> Do you really need to run these two for every link rate?

According to Bspec on link training failure when we change the frequency,
it should follow the enable sequence steps to enable PLL and port which
include configuring DDI_BUF_TRANS and DDI_BUF_CTL.


> 
> > +			intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> > +			ret = intel_dp_start_link_train(intel_dp);
> > +			if (ret)
> > +				break;
> 
> Where do you stop link training on failure? Perhaps:
> 
> ret = intel_dp_start_link_train(intel_dp);
> intel_dp_stop_link_train(intel_dp);
> if (ret)
> 	break;
> 
> and remove the stop on the success path?
>

I will make this change and resubmit.

 
> > +
> > +			/* Disable port followed by PLL for next retry/clean up */
> > +			intel_ddi_post_disable(encoder, NULL, NULL);
> > +			pll->funcs.disable(dev_priv, pll);
> > +			if (link_rate == 540000)
> > +				link_rate = 270000;
> > +			else if (link_rate == 270000)
> > +				link_rate = 162000;
> > +			else
> > +				link_rate_not_found = false;
> > +		}
> > +		if (ret) {
> > +			DRM_DEBUG_KMS("Link Training successful\n");
> > +			intel_dp_stop_link_train(intel_dp);
> > +			break;
> > +		}
> > +	}
> > +	if (!lane_count)
> > +		DRM_ERROR("Link Training Failed\n");
> > +
> > +	return ret;
> > +}
> > +
> >  void intel_ddi_init(struct drm_device *dev, enum port port)
> >  {
> >  	struct drm_i915_private *dev_priv = to_i915(dev);
> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > index 07f0159..0df49e8 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > @@ -309,9 +309,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> >  				DP_TRAINING_PATTERN_DISABLE);
> >  }
> >  
> > -void
> > +bool
> >  intel_dp_start_link_train(struct intel_dp *intel_dp)
> >  {
> > -	intel_dp_link_training_clock_recovery(intel_dp);
> > -	intel_dp_link_training_channel_equalization(intel_dp);
> > +	bool ret;
> > +
> > +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
> > +		ret = intel_dp_link_training_channel_equalization(intel_dp);
> > +		if (ret)
> > +			return true;
> > +	}
> > +	return false;
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index e5bc976..342a2d5 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -1160,6 +1160,8 @@ void intel_ddi_clock_get(struct intel_encoder *encoder,
> >  			 struct intel_crtc_state *pipe_config);
> >  void intel_ddi_set_vc_payload_alloc(struct drm_crtc *crtc, bool state);
> >  uint32_t ddi_signal_levels(struct intel_dp *intel_dp);
> > +bool intel_ddi_link_train(struct intel_dp *intel_dp, int max_link_rate,
> > +			 uint8_t max_lane_count, bool link_mst);
> >  struct intel_shared_dpll *intel_ddi_get_link_dpll(struct intel_dp *intel_dp,
> >  						  int clock);
> >  unsigned int intel_fb_align_height(struct drm_device *dev,
> > @@ -1381,7 +1383,7 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> >  void intel_dp_set_link_params(struct intel_dp *intel_dp,
> >  			      int link_rate, uint8_t lane_count,
> >  			      bool link_mst);
> > -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> > +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
> >  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
> >  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
> >  void intel_dp_encoder_reset(struct drm_encoder *encoder);
> > -- 
> > 1.9.1
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx