Re: [PATCH 5/5] drm/i915: force full detect on sink count change

[Ander Conselvan De Oliveira <conselvan2@gmail.com>]

On Tue, 2016-01-19 at 16:07 +0530, Shubhangi Shrivastava wrote:
> This patch checks for changes in sink count between short pulse
> hpds and forces full detect when there is a change.
> 
> This will allow both detection of hotplug and unplug of panels
> through dongles that give only short pulse for such events.
> 
> v2: changed variable type from u8 to bool (Jani)
>     return immediately if perform_full_detect is set(Siva)
> 
> v3: changed method of determining full detection from using
>     pointer to return code (Siva)
> 
> v4: changed comments to indicate meaning of return value of
>     intel_dp_short_pulse and explain the use of return value
>     from intel_dp_get_dpcd in intel_dp_short_pulse (Ander)
> 
> Tested-by: Nathan D Ciobanu <nathan.d.ciobanu@intel.com>
> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
> Signed-off-by: Shubhangi Shrivastava <shubhangi.shrivastava@intel.com>

Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 33 +++++++++++++++++++++++++++------
>  1 file changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index cdf4919..120d263 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4325,12 +4325,19 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
>   *  2. Configure link according to Receiver Capabilities
>   *  3. Use Link Training from 2.5.3.3 and 3.5.1.3
>   *  4. Check link status on receipt of hot-plug interrupt
> + *
> + * intel_dp_short_pulse -  handles short pulse interrupts
> + * when full detection is not required.
> + * Returns %true if short pulse is handled and full detection
> + * is NOT required and %false otherwise.
>   */
> -static void
> +static bool
>  intel_dp_short_pulse(struct intel_dp *intel_dp)
>  {
>  	struct drm_device *dev = intel_dp_to_dev(intel_dp);
>  	u8 sink_irq_vector;
> +	u8 old_sink_count = intel_dp->sink_count;
> +	bool ret;
>  
>  	/*
>  	 * Clearing compliance test variables to allow capturing
> @@ -4340,9 +4347,17 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
>  	intel_dp->compliance_test_type = 0;
>  	intel_dp->compliance_test_data = 0;
>  
> -	/* Now read the DPCD to see if it's actually running */
> -	if (!intel_dp_get_dpcd(intel_dp)) {
> -		return;
> +	/*
> +	 * Now read the DPCD to see if it's actually running
> +	 * If the current value of sink count doesn't match with
> +	 * the value that was stored earlier or dpcd read failed
> +	 * we need to do full detection
> +	 */
> +	ret = intel_dp_get_dpcd(intel_dp);
> +
> +	if ((old_sink_count != intel_dp->sink_count) || !ret) {
> +		/* No need to proceed if we are going to do full detect */
> +		return false;
>  	}
>  
>  	/* Try to read the source of the interrupt */
> @@ -4362,6 +4377,8 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
>  	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
>  	intel_dp_check_link_status(intel_dp);
>  	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +	return true;
>  }
>  
>  /* XXX this is probably wrong for multiple downstream ports */
> @@ -5086,8 +5103,12 @@ intel_dp_hpd_pulse(struct intel_digital_port
> *intel_dig_port, bool long_hpd)
>  			}
>  		}
>  
> -		if (!intel_dp->is_mst)
> -			intel_dp_short_pulse(intel_dp);
> +		if (!intel_dp->is_mst) {
> +			if (!intel_dp_short_pulse(intel_dp)) {
> +				intel_dp_long_pulse(intel_dp
> ->attached_connector);
> +				goto put_power;
> +			}
> +		}
>  	}
>  
>  	ret = IRQ_HANDLED;
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