Re: [PATCH 4/4] drm/i915: force full detect on sink count change

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Aug 27, 2015 at 02:18:32PM +0530, Sivakumar Thulasimani wrote:
> From: "Thulasimani,Sivakumar" <sivakumar.thulasimani@intel.com>
> 
> 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)
> 
> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>

That's still incomplete since in the hotplug work function we check
whether ->detect status has changed. If that doesn't happen (e.g. sink
count changes from 1->2 or whatever) then we'll fail to generate the
required uevent.

I suspect the only clean way to fix this is to merge all the dp hpd
handling together into one place and stop using ->detect for some parts of
it. Then we would have one place only that decides whether anything
changed, and whether we need to send anything to userspace or not.
-Daniel

> ---
>  drivers/gpu/drm/i915/intel_dp.c |   27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 834f513..279e52c 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4370,26 +4370,39 @@ go_again:
>   *  4. Check link status on receipt of hot-plug interrupt
>   */
>  static void
> -intel_dp_check_link_status(struct intel_dp *intel_dp)
> +intel_dp_check_link_status(struct intel_dp *intel_dp, bool *perform_full_detect)
>  {
>  	struct drm_device *dev = intel_dp_to_dev(intel_dp);
>  	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
>  	struct intel_crtc *crtc =
>  		to_intel_crtc(dp_to_dig_port(intel_dp)->base.base.crtc);
>  	u8 sink_irq_vector;
> +	u8 old_sink_count = intel_dp->sink_count;
> +	bool ret;
>  	u8 link_status[DP_LINK_STATUS_SIZE];
>  
>  	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
>  
> +	*perform_full_detect = false;
> +
>  	/* Try to read receiver status if the link appears to be up */
>  	if (!intel_dp_get_link_status(intel_dp, link_status)) {
>  		return;
>  	}
>  
> -	/* Now read the DPCD to see if it's actually running */
> -	if (!intel_dp_get_dpcd(intel_dp)) {
> +	/* Now read the DPCD to see if it's actually running
> +	 * Don't return immediately if dpcd read failed,
> +	 * if sink count was 1 and dpcd read failed we need
> +	 * to do full detection
> +	 */
> +	ret = intel_dp_get_dpcd(intel_dp);
> +
> +	if (old_sink_count != intel_dp->sink_count)
> +		*perform_full_detect = true;
> +
> +	/* No need to proceed if we are going to do full detect */
> +	if (!ret || *perform_full_detect)
>  		return;
> -	}
>  
>  	if (!intel_encoder->base.crtc)
>  		return;
> @@ -5031,13 +5044,17 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
>  		}
>  
>  		if (!intel_dp->is_mst) {
> +			bool full_detect;
>  			/*
>  			 * we'll check the link status via the normal hot plug path later -
>  			 * but for short hpds we should check it now
>  			 */
>  			drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> -			intel_dp_check_link_status(intel_dp);
> +			intel_dp_check_link_status(intel_dp, &full_detect);
>  			drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +			if (full_detect)
> +				goto put_power;
>  		}
>  	}
>  
> -- 
> 1.7.9.5
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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