drm/bridge: adv7511: Fix mutex deadlock when interrupts are disabled

When the adv7511 i2c client doesn't have an interrupt line, we observe a
deadlock on caused by trying to lock drm device's mode_config.mutex twice
in the same context.

Here is the sequence that causes it:

ioctl DRM_IOCTL_MODE_GETCONNECTOR from userspace
  drm_mode_getconnector (acquires mode_config mutex)
    connector->fill_modes()
    drm_helper_probe_single_connector_modes
      connector_funcs->get_modes
	adv7511_encoder_get_modes
	  adv7511_get_edid_block
	    adv7511_irq_process
	      drm_helper_hpd_irq_event (acquires mode_config mutex again)

In adv7511_irq_process, don't call drm_helper_hpd_irq_event when not
called from the interrupt handler. It doesn't serve any purpose there
anyway.

Signed-off-by: Archit Taneja <architt@codeaurora.org>

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
index c2642f9..1fff0ab 100644 (file)
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -427,7 +427,7 @@ static bool adv7511_hpd(struct adv7511 *adv7511)
        return false;
 }
 
-static int adv7511_irq_process(struct adv7511 *adv7511)
+static int adv7511_irq_process(struct adv7511 *adv7511, bool process_hpd)
 {
        unsigned int irq0, irq1;
        int ret;
@@ -443,7 +443,7 @@ static int adv7511_irq_process(struct adv7511 *adv7511)
        regmap_write(adv7511->regmap, ADV7511_REG_INT(0), irq0);
        regmap_write(adv7511->regmap, ADV7511_REG_INT(1), irq1);
 
-       if (irq0 & ADV7511_INT0_HPD && adv7511->bridge.encoder)
+       if (process_hpd && irq0 & ADV7511_INT0_HPD && adv7511->bridge.encoder)
                drm_helper_hpd_irq_event(adv7511->connector.dev);
 
        if (irq0 & ADV7511_INT0_EDID_READY || irq1 & ADV7511_INT1_DDC_ERROR) {
@@ -461,7 +461,7 @@ static irqreturn_t adv7511_irq_handler(int irq, void *devid)
        struct adv7511 *adv7511 = devid;
        int ret;
 
-       ret = adv7511_irq_process(adv7511);
+       ret = adv7511_irq_process(adv7511, true);
        return ret < 0 ? IRQ_NONE : IRQ_HANDLED;
 }
 
@@ -478,7 +478,7 @@ static int adv7511_wait_for_edid(struct adv7511 *adv7511, int timeout)
                                adv7511->edid_read, msecs_to_jiffies(timeout));
        } else {
                for (; timeout > 0; timeout -= 25) {
-                       ret = adv7511_irq_process(adv7511);
+                       ret = adv7511_irq_process(adv7511, false);
                        if (ret < 0)
                                break;