Date:   Fri, 10 Aug 2018 13:02:15 +0000
From:   "Lisovskiy, Stanislav" <stanislav.lisovskiy@...el.com>
To:     "Mun, Gwan-gyeong" <gwan-gyeong.mun@...el.com>,
        "jani.nikula@...ux.intel.com" <jani.nikula@...ux.intel.com>
CC:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Vivi, Rodrigo" <rodrigo.vivi@...el.com>,
        "airlied@...ux.ie" <airlied@...ux.ie>
Subject: Re: [Intel-gfx] [v3] drm/i915: Add detection of changing of edid on
 between suspend and resume

On Thu, 2018-08-09 at 14:13 +0300, Gwan-gyeong Mun wrote:
> The hotplug detection routine of i915 uses
> drm_helper_hpd_irq_event(). This
> helper can detect changing of status of connector, but it can not
> detect
> changing of edid.
> 
> Following scenario requires detection of changing of edid.
> 
>  1) plug display device to a connector
>  2) system suspend
>  3) unplug 1)'s display device and plug the other display device to a
> connector
>  4) system resume
> 
> It adds edid check routine when a connector status still remains as
> "connector_status_connected".
> 
> v2: Add NULL check before comparing of EDIDs.
> 
> Testcase: igt/kms_chamelium/hdmi-edid-change-during-hibernate
> Testcase: igt/kms_chamelium/hdmi-edid-change-during-suspend
> Testcase: igt/kms_chamelium/dp-edid-change-during-hibernate
> Testcase: igt/kms_chamelium/dp-edid-change-during-suspend
> 
> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>
> ---
>  drivers/gpu/drm/i915/intel_hotplug.c | 84
> +++++++++++++++++++++++++++-
>  1 file changed, 83 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hotplug.c
> b/drivers/gpu/drm/i915/intel_hotplug.c
> index 648a13c6043c..965f2d771fc0 100644
> --- a/drivers/gpu/drm/i915/intel_hotplug.c
> +++ b/drivers/gpu/drm/i915/intel_hotplug.c
> @@ -507,6 +507,88 @@ void intel_hpd_init(struct drm_i915_private
> *dev_priv)
>  	}
>  }
>  
> +/**
> + * intel_hpd_irq_event - hotplug processing
> + * @dev: drm_device
> + *
> + * Drivers can use this function to run a detect cycle on all
> connectors which
> + * have the DRM_CONNECTOR_POLL_HPD flag set in their &polled member.
> All other
> + * connectors are ignored, which is useful to avoid reprobing fixed
> panels.
> + *
> + * This function is useful for drivers which can't or don't track
> hotplug interrupts
> + * for each connector. This function is based on
> drm_helper_hpd_irq_event() helper
> + * function and besides it adds edid check routine when a connector
> status still
> + * remains as "connector_status_connected".
> + *
> + * Following scenario requires detection of changing of edid.
> + *  1) plug display device to a connector
> + *  2) system suspend
> + *  3) unplug 1)'s display device and plug the other display device
> to a connector
> + *  4) system resume
> +
> + * This function must be called from process context with no mode
> + * setting locks held.
> + *
> + * Note that a connector can be both polled and probed from the
> hotplug handler,
> + * in case the hotplug interrupt is known to be unreliable.
> + */
> +static bool intel_hpd_irq_event(struct drm_device *dev)
> +{
> +	struct drm_connector *connector;
> +	struct drm_connector_list_iter conn_iter;
> +	enum drm_connector_status old_status, cur_status;
> +	struct edid *old_edid;
> +	bool changed = false;
> +
> +	if (!dev->mode_config.poll_enabled)
> +		return false;
> +
> +	mutex_lock(&dev->mode_config.mutex);
> +	drm_connector_list_iter_begin(dev, &conn_iter);
> +	drm_for_each_connector_iter(connector, &conn_iter) {
> +		/* Only handle HPD capable connectors. */
> +		if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
> +			continue;
> +
> +		old_status = connector->status;
> +		old_edid = to_intel_connector(connector)-
> >detect_edid;
> +
> +		cur_status = drm_helper_probe_detect(connector,
> NULL, false);
> +		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from
> %s to %s\n",
> +			      connector->base.id, connector->name,
> +			      drm_get_connector_status_name(old_stat
> us),
> +			      drm_get_connector_status_name(cur_stat
> us));
> +
> +		if (old_status != cur_status)
> +			changed = true;
> +
> +		/* Check changing of edid when a connector status
> still remains
> +		 * as "connector_status_connected".
> +		 */
> +		if (old_status == cur_status &&
> +		    cur_status == connector_status_connected) {
> +			struct edid *cur_edid =
> to_intel_connector(connector)->detect_edid;
> +
> +			if (!old_edid || !cur_edid)
> +				continue;
> +
> +			if (memcmp(old_edid, cur_edid,
> sizeof(*cur_edid))) {
> +				changed = true;
> +				DRM_DEBUG_KMS("[CONNECTOR:%d:%s]
> edid updated\n",
> +					      connector->base.id,
> +					      connector->name);
> +			}
> +		}
> +	}
> +	drm_connector_list_iter_end(&conn_iter);
> +	mutex_unlock(&dev->mode_config.mutex);
> +
> +	if (changed)
> +		drm_kms_helper_hotplug_event(dev);
> +
> +	return changed;
> +}
> +
>  static void i915_hpd_poll_init_work(struct work_struct *work)
>  {
>  	struct drm_i915_private *dev_priv =
> @@ -552,7 +634,7 @@ static void i915_hpd_poll_init_work(struct
> work_struct *work)
>  	 * in the middle of disabling polling
>  	 */
>  	if (!enabled)
> -		drm_helper_hpd_irq_event(dev);
> +		intel_hpd_irq_event(dev);
>  }

Just wondering, as I saw previously drm_helper_hpd_irq_event function
was used, which basically does the same thing, except doing memcmp
for detecting the edid change. Is it only Intel specific change? As we
could just add this modification to existing helper function or add
another helper function to the drm (drm_probe_helper.c), so that it is
also usable elsewhere..

>  
>  /**
-- 
Best Regards,

Lisovskiy Stanislav

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