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Commit b872a8e1 authored by Russell King's avatar Russell King
Browse files

drm: bridge/dw_hdmi: fix phy enable/disable handling 



The dw_hdmi enable/disable handling is particularly weak in several
regards:
* The hotplug interrupt could call hdmi_poweron() or hdmi_poweroff()
  while DRM is setting a mode, which could race with a mode being set.
* Hotplug will always re-enable the phy whenever it detects an active
  hotplug signal, even if DRM has disabled the output.

Resolve all of these by introducing a mutex to prevent races, and a
state-tracking bool so we know whether DRM wishes the output to be
enabled.  We choose to use our own mutex rather than ->struct_mutex
so that we can still process interrupts in a timely fashion.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 2fada109

drivers/gpu/drm/bridge/dw_hdmi.c

+22 −7
Original line number Diff line number Diff line
@@ -125,6 +125,9 @@ struct dw_hdmi { 
	bool sink_is_hdmi;

	bool sink_has_audio;



	struct mutex mutex;		/* for state below and previous_mode */

	bool disabled;			/* DRM has disabled our bridge */



	spinlock_t audio_lock;

	struct mutex audio_mutex;

	unsigned int sample_rate;
@@ -1375,8 +1378,12 @@ static void dw_hdmi_bridge_mode_set(struct drm_bridge *bridge, 
{

	struct dw_hdmi *hdmi = bridge->driver_private;



	mutex_lock(&hdmi->mutex);



	/* Store the display mode for plugin/DKMS poweron events */

	memcpy(&hdmi->previous_mode, mode, sizeof(hdmi->previous_mode));



	mutex_unlock(&hdmi->mutex);

}



static bool dw_hdmi_bridge_mode_fixup(struct drm_bridge *bridge,
@@ -1390,14 +1397,20 @@ static void dw_hdmi_bridge_disable(struct drm_bridge *bridge) 
{

	struct dw_hdmi *hdmi = bridge->driver_private;



	mutex_lock(&hdmi->mutex);

	hdmi->disabled = true;

	dw_hdmi_poweroff(hdmi);

	mutex_unlock(&hdmi->mutex);

}



static void dw_hdmi_bridge_enable(struct drm_bridge *bridge)

{

	struct dw_hdmi *hdmi = bridge->driver_private;



	mutex_lock(&hdmi->mutex);

	dw_hdmi_poweron(hdmi);

	hdmi->disabled = false;

	mutex_unlock(&hdmi->mutex);

}



static void dw_hdmi_bridge_nop(struct drm_bridge *bridge)
@@ -1520,20 +1533,20 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id) 
	phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0);



	if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {

		hdmi_modb(hdmi, ~phy_int_pol, HDMI_PHY_HPD, HDMI_PHY_POL0);

		mutex_lock(&hdmi->mutex);

		if (phy_int_pol & HDMI_PHY_HPD) {

			dev_dbg(hdmi->dev, "EVENT=plugin\n");



			hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0);



			if (!hdmi->disabled)

				dw_hdmi_poweron(hdmi);

		} else {

			dev_dbg(hdmi->dev, "EVENT=plugout\n");



			hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD,

				  HDMI_PHY_POL0);



			if (!hdmi->disabled)

				dw_hdmi_poweroff(hdmi);

		}

		mutex_unlock(&hdmi->mutex);

		drm_helper_hpd_irq_event(hdmi->bridge->dev);

	}
@@ -1601,7 +1614,9 @@ int dw_hdmi_bind(struct device *dev, struct device *master, 
	hdmi->sample_rate = 48000;

	hdmi->ratio = 100;

	hdmi->encoder = encoder;

	hdmi->disabled = true;



	mutex_init(&hdmi->mutex);

	mutex_init(&hdmi->audio_mutex);

	spin_lock_init(&hdmi->audio_lock);