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

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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>
This commit is contained in:
Archit Taneja 2016-06-15 16:20:45 +05:30
parent c582778900
commit f0bfcc22d9
1 changed files with 4 additions and 4 deletions
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8
drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
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@ -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;