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 interrupt context. It doesn't serve any purpose there anyway.

Signed-off-by: Archit Taneja <architt at codeaurora.org>
---
 drivers/gpu/drm/i2c/adv7511.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i2c/adv7511.c b/drivers/gpu/drm/i2c/adv7511.c
index 2aaa3c8..cf5bb29 100644
--- a/drivers/gpu/drm/i2c/adv7511.c
+++ b/drivers/gpu/drm/i2c/adv7511.c
@@ -422,7 +422,7 @@ 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;
@@ -438,7 +438,7 @@ 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_HDP && adv7511->encoder)
+       if (process_hpd && irq0 & ADV7511_INT0_HDP && adv7511->encoder)
                drm_helper_hpd_irq_event(adv7511->encoder->dev);

        if (irq0 & ADV7511_INT0_EDID_READY || irq1 & ADV7511_INT1_DDC_ERROR) {
@@ -456,7 +456,7 @@ 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;
 }

@@ -473,7 +473,7 @@ 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;

-- 
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