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: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index cef31d5..c5c4553 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -125,6 +125,9 @@
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 @@
{
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 @@
{
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 @@
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);
-
- dw_hdmi_poweron(hdmi);
+ 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);
-
- dw_hdmi_poweroff(hdmi);
+ if (!hdmi->disabled)
+ dw_hdmi_poweroff(hdmi);
}
+ mutex_unlock(&hdmi->mutex);
drm_helper_hpd_irq_event(hdmi->bridge->dev);
}
@@ -1601,7 +1614,9 @@
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);