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

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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>
This commit is contained in:
Russell King 2015-06-05 12:22:46 +01:00
parent 2fada109cf
commit b872a8e16b
1 changed files with 22 additions and 7 deletions
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29
drivers/gpu/drm/bridge/dw_hdmi.c
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@ -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);
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 @@ 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);