From 8fc8f7da9719c2d28fb32cdd74af9b6cd9bac20a Mon Sep 17 00:00:00 2001
From: Thierry Reding <treding@nvidia.com>
Date: Tue, 21 Oct 2014 14:00:09 +0200
Subject: drm/tegra: Enable the hotplug interrupt only when necessary

The hotplug handling needs access to the DRM device, which only appears
at ->init() time. Disable interrupts up until that time. Similarly, when
an output is removed, disable the hotplug interrupt again because the
DRM device (and with it the hotplug infrastructure) is going away.

Also make sure to only access the DRM device if it's available. Given
the above change for the hotplug interrupt this should really never
happen, but the extra check doesn't hurt either.

Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --git a/drivers/gpu/drm/tegra/output.c b/drivers/gpu/drm/tegra/output.c
index e6cfbde..022462d3 100644
--- a/drivers/gpu/drm/tegra/output.c
+++ b/drivers/gpu/drm/tegra/output.c
@@ -183,7 +183,8 @@ static irqreturn_t hpd_irq(int irq, void *data)
 {
 	struct tegra_output *output = data;
 
-	drm_helper_hpd_irq_event(output->connector.dev);
+	if (output->connector.dev)
+		drm_helper_hpd_irq_event(output->connector.dev);
 
 	return IRQ_HANDLED;
 }
@@ -255,6 +256,13 @@ int tegra_output_probe(struct tegra_output *output)
 		}
 
 		output->connector.polled = DRM_CONNECTOR_POLL_HPD;
+
+		/*
+		 * Disable the interrupt until the connector has been
+		 * initialized to avoid a race in the hotplug interrupt
+		 * handler.
+		 */
+		disable_irq(output->hpd_irq);
 	}
 
 	return 0;
@@ -320,10 +328,24 @@ int tegra_output_init(struct drm_device *drm, struct tegra_output *output)
 
 	output->encoder.possible_crtcs = 0x3;
 
+	/*
+	 * The connector is now registered and ready to receive hotplug events
+	 * so the hotplug interrupt can be enabled.
+	 */
+	if (gpio_is_valid(output->hpd_gpio))
+		enable_irq(output->hpd_irq);
+
 	return 0;
 }
 
 int tegra_output_exit(struct tegra_output *output)
 {
+	/*
+	 * The connector is going away, so the interrupt must be disabled to
+	 * prevent the hotplug interrupt handler from potentially crashing.
+	 */
+	if (gpio_is_valid(output->hpd_gpio))
+		disable_irq(output->hpd_irq);
+
 	return 0;
 }
-- 
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