On Wed, Oct 07, 2015 at 12:05:37PM +0800, Yakir Yang wrote:
On 08/09/2015 12:04 AM, Russell King wrote:
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
drivers/gpu/drm/bridge/dw_hdmi.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c index 7b8a4e942a71..0ee188930d26 100644 --- a/drivers/gpu/drm/bridge/dw_hdmi.c +++ b/drivers/gpu/drm/bridge/dw_hdmi.c @@ -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;
@@ -1389,8 +1392,12 @@ 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, @@ -1404,14 +1411,20 @@ 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) @@ -1534,20 +1547,20 @@ 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);
hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0);dw_hdmi_poweron(hdmi);
if (!hdmi->disabled)dw_hdmi_poweron(hdmi);
hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD,HDMI_PHY_POL0);dw_hdmi_poweroff(hdmi);
if (!hdmi->disabled)dw_hdmi_poweroff(hdmi);Just like my reply on 08/12, I thought this could be removed, so poweron/poweroff would only be called with bridge->enable/ bridge->disable, them maybe no need mutex here.
The bridge enable/disable methods do not get called on hotplug changes.
[ 1.363011] dwhdmi-imx 120000.hdmi: Detected HDMI controller 0x13:0xa:0xa0:0xc1 [ 1.371341] dwhdmi-imx 120000.hdmi: dw_hdmi_irq(I:RX----,HPD P:RX3210,HPD S:RX----,HPD) [ 1.381345] imx-drm display-subsystem: bound 120000.hdmi (ops dw_hdmi_imx_ops) [ 1.448691] dwhdmi-imx 120000.hdmi: dw_hdmi_bridge_disable() [ 1.450963] dwhdmi-imx 120000.hdmi: dw_hdmi_bridge_enable()
and then unplugging and re-plugging the HDMI cable:
[ 68.307505] dwhdmi-imx 120000.hdmi: dw_hdmi_irq(I:RX----,HPD P:RX3210,--- S:RX----,---) [ 73.813970] dwhdmi-imx 120000.hdmi: dw_hdmi_irq(I:RX----,HPD P:RX3210,HPD S:RX----,HPD)
As you can see, during the period of disconnection for five seconds, dw_hdmi_bridge_disable() was not called.
So, without the code above, we'd be needlessly wasting power with the bridge enabled, trying to drive a disconnected display.