[Intel-gfx] [PATCH v3 2/2] drm/i915: Enable hotplug retry

[Imre Deak]

On Fri, Jun 28, 2019 at 02:39:21PM -0700, José Roberto de Souza wrote:
> Right now we are aware of two cases that needs another hotplug retry:
> - Unpowered type-c dongles
> - HDMI slow unplug
> 
> Both have a complete explanation in the code to schedule another run
> of the hotplug handler.
> 
> It could have more checks to just trigger the retry in those two
> specific cases but why would sink signal a long pulse if there is
> no change? Also the drawback of running the hotplug handler again
> is really low and that could fix another cases that we are not
> aware.
> 
> Also retrying for old DP ports(non-DDI) to make it consistent and not
> cause CI failures if those systems are connected to chamelium boards
> that will be used to simulate the issues reported in here.
> 
> v2: Also retrying for old DP ports(non-DDI)(Imre)
> 
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Imre Deak <imre.deak at intel.com>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c  | 21 +++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_dp.c   |  3 +++
>  drivers/gpu/drm/i915/display/intel_hdmi.c | 28 ++++++++++++++++++++++-
>  3 files changed, 51 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 53009984e046..d7df1940b826 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -4086,6 +4086,7 @@ intel_ddi_hotplug(struct intel_encoder *encoder,
>  		  struct intel_connector *connector,
>  		  bool irq_received)
>  {
> +	struct intel_digital_port *dig_port = enc_to_dig_port(&encoder->base);
>  	struct drm_modeset_acquire_ctx ctx;
>  	enum intel_hotplug_state state;
>  	int ret;
> @@ -4112,6 +4113,26 @@ intel_ddi_hotplug(struct intel_encoder *encoder,
>  	drm_modeset_acquire_fini(&ctx);
>  	WARN(ret, "Acquiring modeset locks failed with %i\n", ret);
>  
> +	/*
> +	 * Unpowered type-c dongles can take some time to boot and be
> +	 * responsible, so here giving some time to those dongles to power up
> +	 * and then retrying the probe.
> +	 *
> +	 * On many platforms the HDMI live state signal is known to be
> +	 * unreliable, so we can't use it to detect if a sink is connected or
> +	 * not. Instead we detect if it's connected based on whether we can
> +	 * read the EDID or not. That in turn has a problem during disconnect,
> +	 * since the HPD interrupt may be raised before the DDC lines get
> +	 * disconnected (due to how the required length of DDC vs. HPD
> +	 * connector pins are specified) and so we'll still be able to get a
> +	 * valid EDID. To solve this schedule another detection cycle if this
> +	 * time around we didn't detect any change in the sink's connection
> +	 * status.
> +	 */
> +	if (state == INTEL_HOTPLUG_NOCHANGE && irq_received &&
> +	    !dig_port->dp.is_mst)
> +		state = INTEL_HOTPLUG_RETRY;
> +
>  	return state;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 95d0da9d1bac..8eb479daa8a8 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4906,6 +4906,9 @@ intel_dp_hotplug(struct intel_encoder *encoder,
>  	drm_modeset_acquire_fini(&ctx);
>  	WARN(ret, "Acquiring modeset locks failed with %i\n", ret);

Nit: could add a short comment, that a long HPD interrupt that doesn't
result in a connector state change could be just a transient state, so
we retry the detection.

> +	if (state == INTEL_HOTPLUG_NOCHANGE && irq_received)
> +		state = INTEL_HOTPLUG_RETRY;
> +
>  	return state;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index 0ebec69bbbfc..5ed91caf3b4d 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -3143,6 +3143,32 @@ void intel_hdmi_init_connector(struct intel_digital_port *intel_dig_port,
>  		DRM_DEBUG_KMS("CEC notifier get failed\n");
>  }
>  
> +static enum intel_hotplug_state
> +intel_hdmi_hotplug(struct intel_encoder *encoder,
> +		   struct intel_connector *connector, bool irq_received)
> +{
> +	enum intel_hotplug_state state;
> +
> +	state = intel_encoder_hotplug(encoder, connector, irq_received);
> +
> +	/*
> +	 * On many platforms the HDMI live state signal is known to be
> +	 * unreliable, so we can't use it to detect if a sink is connected or
> +	 * not. Instead we detect if it's connected based on whether we can
> +	 * read the EDID or not. That in turn has a problem during disconnect,
> +	 * since the HPD interrupt may be raised before the DDC lines get
> +	 * disconnected (due to how the required length of DDC vs. HPD
> +	 * connector pins are specified) and so we'll still be able to get a
> +	 * valid EDID. To solve this schedule another detection cycle if this
> +	 * time around we didn't detect any change in the sink's connection
> +	 * status.
> +	 */

This is the same description of the issue that DDI encoders have, so
could be just replaced with a reference to the intel_ddi_hotplug() func.

Looks ok:
Reviewed-by: Imre Deak <imre.deak at intel.com>

> +	if (state == INTEL_HOTPLUG_NOCHANGE && irq_received)
> +		state = INTEL_HOTPLUG_RETRY;
> +
> +	return state;
> +}
> +
>  void intel_hdmi_init(struct drm_i915_private *dev_priv,
>  		     i915_reg_t hdmi_reg, enum port port)
>  {
> @@ -3166,7 +3192,7 @@ void intel_hdmi_init(struct drm_i915_private *dev_priv,
>  			 &intel_hdmi_enc_funcs, DRM_MODE_ENCODER_TMDS,
>  			 "HDMI %c", port_name(port));
>  
> -	intel_encoder->hotplug = intel_encoder_hotplug;
> +	intel_encoder->hotplug = intel_hdmi_hotplug;
>  	intel_encoder->compute_config = intel_hdmi_compute_config;
>  	if (HAS_PCH_SPLIT(dev_priv)) {
>  		intel_encoder->disable = pch_disable_hdmi;
> -- 
> 2.22.0
>