Re: [PATCH 2/2] drm/i915: Do not get aux power for disconnected DP ports

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

On Mon, Sep 24, 2018 at 06:16:49PM -0700, José Roberto de Souza wrote:
> For ICL type-c ports there is a aux power restriction, it can only be
> enabled while there is sink connected.

That can't be entirely true because it's super racy. I was talking
with Imre about this mess at some point, and IIRC we came up with
some half decent theories on how we might handle this mess in a
sane manner. IIRC it was something along the lines of: the tbt vs.
other mode knob defines which power well we can enable, and so
while we're doing something with the port in one mode or the other
we must not try to use the port in the other mode. Ie. we need to
properly track which mode the port is in and if there's an event
that requires switching modes we have to wait until the previous
use of the other mode has stopped.

> 
> BSpec: 21750
> 
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 6b4c19123f2a..48fd38cd4ba4 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5019,19 +5019,27 @@ intel_dp_long_pulse(struct intel_connector *connector,
>  	struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
>  	enum drm_connector_status status;
>  	u8 sink_irq_vector = 0;
> +	bool got_aux_power;
>  
>  	WARN_ON(!drm_modeset_is_locked(&dev_priv->drm.mode_config.connection_mutex));
>  
> +	/* Can't disconnect eDP */
> +	if (!intel_dp_is_edp(intel_dp) &&
> +	    !intel_digital_port_connected(&dp_to_dig_port(intel_dp)->base)) {
> +		status = connector_status_disconnected;
> +		got_aux_power = false;
> +		goto port_disconnected;
> +	}
> +
>  	intel_display_power_get(dev_priv, intel_dp->aux_power_domain);
> +	got_aux_power = true;
>  
> -	/* Can't disconnect eDP */
>  	if (intel_dp_is_edp(intel_dp))
>  		status = edp_detect(intel_dp);
> -	else if (intel_digital_port_connected(&dp_to_dig_port(intel_dp)->base))
> -		status = intel_dp_detect_dpcd(intel_dp);
>  	else
> -		status = connector_status_disconnected;
> +		status = intel_dp_detect_dpcd(intel_dp);
>  
> +port_disconnected:
>  	if (status == connector_status_disconnected) {
>  		memset(&intel_dp->compliance, 0, sizeof(intel_dp->compliance));
>  
> @@ -5122,7 +5130,8 @@ intel_dp_long_pulse(struct intel_connector *connector,
>  	if (status != connector_status_connected && !intel_dp->is_mst)
>  		intel_dp_unset_edid(intel_dp);
>  
> -	intel_display_power_put(dev_priv, intel_dp->aux_power_domain);
> +	if (got_aux_power)
> +		intel_display_power_put(dev_priv, intel_dp->aux_power_domain);
>  	return status;
>  }
>  
> -- 
> 2.19.0
> 
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-- 
Ville Syrjälä
Intel
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