drm/tegra: dp - Implement hotplug detection in work queue

Calling the drm_helper_hpd_irq_event() helper can sleep, so instead of
invoking it directly from the interrupt handler, schedule a work queue
and run it from there.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dpaux.c

@@ -15,6 +15,7 @@
 #include <linux/platform_device.h>
 #include <linux/reset.h>
 #include <linux/regulator/consumer.h>
+#include <linux/workqueue.h>
 
 #include <drm/drm_dp_helper.h>
 #include <drm/drm_panel.h>
@@ -41,6 +42,7 @@ struct tegra_dpaux {
 	struct regulator *vdd;
 
 	struct completion complete;
+	struct work_struct work;
 	struct list_head list;
 };
 
@@ -49,6 +51,11 @@ static inline struct tegra_dpaux *to_dpaux(struct drm_dp_aux *aux)
 	return container_of(aux, struct tegra_dpaux, aux);
 }
 
+static inline struct tegra_dpaux *work_to_dpaux(struct work_struct *work)
+{
+	return container_of(work, struct tegra_dpaux, work);
+}
+
 static inline unsigned long tegra_dpaux_readl(struct tegra_dpaux *dpaux,
 					      unsigned long offset)
 {
@@ -231,6 +238,14 @@ static ssize_t tegra_dpaux_transfer(struct drm_dp_aux *aux,
 	return ret;
 }
 
+static void tegra_dpaux_hotplug(struct work_struct *work)
+{
+	struct tegra_dpaux *dpaux = work_to_dpaux(work);
+
+	if (dpaux->output)
+		drm_helper_hpd_irq_event(dpaux->output->connector.dev);
+}
+
 static irqreturn_t tegra_dpaux_irq(int irq, void *data)
 {
 	struct tegra_dpaux *dpaux = data;
@@ -241,16 +256,8 @@ static irqreturn_t tegra_dpaux_irq(int irq, void *data)
 	value = tegra_dpaux_readl(dpaux, DPAUX_INTR_AUX);
 	tegra_dpaux_writel(dpaux, value, DPAUX_INTR_AUX);
 
-	if (value & DPAUX_INTR_PLUG_EVENT) {
-		if (dpaux->output) {
-			drm_helper_hpd_irq_event(dpaux->output->connector.dev);
-		}
-	}
-
-	if (value & DPAUX_INTR_UNPLUG_EVENT) {
-		if (dpaux->output)
-			drm_helper_hpd_irq_event(dpaux->output->connector.dev);
-	}
+	if (value & (DPAUX_INTR_PLUG_EVENT | DPAUX_INTR_UNPLUG_EVENT))
+		schedule_work(&dpaux->work);
 
 	if (value & DPAUX_INTR_IRQ_EVENT) {
 		/* TODO: handle this */
@@ -273,6 +280,7 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	if (!dpaux)
 		return -ENOMEM;
 
+	INIT_WORK(&dpaux->work, tegra_dpaux_hotplug);
 	init_completion(&dpaux->complete);
 	INIT_LIST_HEAD(&dpaux->list);
 	dpaux->dev = &pdev->dev;
@@ -361,6 +369,8 @@ static int tegra_dpaux_remove(struct platform_device *pdev)
 	list_del(&dpaux->list);
 	mutex_unlock(&dpaux_lock);
 
+	cancel_work_sync(&dpaux->work);
+
 	clk_disable_unprepare(dpaux->clk_parent);
 	reset_control_assert(dpaux->rst);
 	clk_disable_unprepare(dpaux->clk);