drm: adv7511: Fix crash in IRQ handler when no encoder is associated

The ADV7511 is probed before its slave encoder init function associates
it with an encoder. This creates a time window during which hot plug
detection interrupts can occur with an encoder, resulting in a crash in
the IRQ handler.

Fix this by ignoring hot plug detection IRQs when no encoder is
associated yet.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>

drivers/gpu/drm/i2c/adv7511.c

@@ -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)
+	if (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) {