[Intel-gfx] [RFC 08/13] drm/i915: Add support for enabling link status and recovery

[Shankar, Uma]

> -----Original Message-----
> From: Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>
> Sent: Thursday, October 15, 2020 4:23 PM
> To: intel-gfx at lists.freedesktop.org
> Cc: dri-devel at lists.freedesktop.org; Shankar, Uma <uma.shankar at intel.com>;
> Kulkarni, Vandita <vandita.kulkarni at intel.com>; ville.syrjala at linux.intel.com;
> Sharma, Swati2 <swati2.sharma at intel.com>
> Subject: [RFC 08/13] drm/i915: Add support for enabling link status and recovery
> 
> From: Swati Sharma <swati2.sharma at intel.com>
> 
> In this patch enabled support for link status and recovery in i915 driver. HDMI
> link loss indication to upstream DP source is indicated via IRQ_HPD. This is
> followed by reading of HDMI link configuration status
> (HDMI_TX_LINK_ACTIVE_STATUS). If the PCON → HDMI 2.1 link status is off;
> reinitiate frl link training to recover.
> Also, HDMI FRL link error count range for each individual FRL active lane is
> indicated by DOWNSTREAM_HDMI_ERROR_STATUS_LN registers.
> 
> Signed-off-by: Swati Sharma <swati2.sharma at intel.com>
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 47 +++++++++++++++++++++++--
>  1 file changed, 44 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 668165dd2b1a..e6c4cb844e37 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -5955,6 +5955,29 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
>  	return link_ok;
>  }
> 
> +static void
> +intel_dp_handle_hdmi_link_status_change(struct intel_dp *intel_dp) {
> +	bool is_active;
> +	u8 buf = 0;
> +
> +	is_active = drm_dp_pcon_hdmi_link_active(&intel_dp->aux);
> +	if (intel_dp->frl.is_trained && !is_active) {
> +		if (drm_dp_dpcd_readb(&intel_dp->aux,
> DP_PCON_HDMI_LINK_CONFIG_1, &buf) < 0)
> +			return;
> +
> +		buf &=  ~DP_PCON_ENABLE_HDMI_LINK;
> +		if (drm_dp_dpcd_writeb(&intel_dp->aux,
> DP_PCON_HDMI_LINK_CONFIG_1, buf) < 0)
> +			return;
> +
> +		intel_dp->frl.is_trained = false;
> +		intel_dp->frl.trained_rate_gbps = 0;
> +
> +		intel_dp_check_frl_training(intel_dp);
> +		drm_dp_pcon_hdmi_frl_link_error_count(&intel_dp->aux,
> &intel_dp->attached_connector->base);

Just printing the error here may not help in recovery. If FRL is failing may be a TMDS fallback should be
attempted. Also error count should be returned instead of just a print.

> +	}
> +}
> +
>  static bool
>  intel_dp_needs_link_retrain(struct intel_dp *intel_dp)  { @@ -6320,7 +6343,7
> @@ intel_dp_hotplug(struct intel_encoder *encoder,
>  	return state;
>  }
> 
> -static void intel_dp_check_service_irq(struct intel_dp *intel_dp)
> +static void intel_dp_check_device_service_irq(struct intel_dp
> +*intel_dp)
>  {
>  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>  	u8 val;
> @@ -6344,6 +6367,23 @@ static void intel_dp_check_service_irq(struct intel_dp
> *intel_dp)
>  		drm_dbg_kms(&i915->drm, "Sink specific irq unhandled\n");  }
> 
> +static void intel_dp_check_link_service_irq(struct intel_dp *intel_dp)
> +{
> +	u8 val;
> +
> +	if (intel_dp->dpcd[DP_DPCD_REV] < 0x11)
> +		return;
> +
> +	if (drm_dp_dpcd_readb(&intel_dp->aux,
> +			      DP_LINK_SERVICE_IRQ_VECTOR_ESI0, &val) != 1 ||
> !val)

An error message would be handy here.

> +		return;
> +
> +	drm_dp_dpcd_writeb(&intel_dp->aux,
> DP_LINK_SERVICE_IRQ_VECTOR_ESI0,
> +val);

Check for error message here.

> +
> +	if (val & HDMI_LINK_STATUS_CHANGED)
> +		intel_dp_handle_hdmi_link_status_change(intel_dp);
> +}
> +
>  /*
>   * According to DP spec
>   * 5.1.2:
> @@ -6383,7 +6423,8 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
>  		return false;
>  	}
> 
> -	intel_dp_check_service_irq(intel_dp);
> +	intel_dp_check_device_service_irq(intel_dp);
> +	intel_dp_check_link_service_irq(intel_dp);
> 
>  	/* Handle CEC interrupts, if any */
>  	drm_dp_cec_irq(&intel_dp->aux);
> @@ -6815,7 +6856,7 @@ intel_dp_detect(struct drm_connector *connector,
>  	    to_intel_connector(connector)->detect_edid)
>  		status = connector_status_connected;
> 
> -	intel_dp_check_service_irq(intel_dp);
> +	intel_dp_check_device_service_irq(intel_dp);
> 
>  out:
>  	if (status != connector_status_connected && !intel_dp->is_mst)
> --
> 2.17.1