drm/tegra: output: Support low-active hotplug detect

Support low-active hotplug detect signals by storing the GPIO flags
parsed from device tree.

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

drivers/gpu/drm/tegra/drm.h

@@ -12,6 +12,7 @@
 
 #include <uapi/drm/tegra_drm.h>
 #include <linux/host1x.h>
+#include <linux/of_gpio.h>
 
 #include <drm/drmP.h>
 #include <drm/drm_crtc_helper.h>
@@ -200,6 +201,7 @@ struct tegra_output {
 	const struct edid *edid;
 	unsigned int hpd_irq;
 	int hpd_gpio;
+	enum of_gpio_flags hpd_gpio_flags;
 
 	struct drm_encoder encoder;
 	struct drm_connector connector;

drivers/gpu/drm/tegra/output.c

@@ -7,8 +7,6 @@
  * published by the Free Software Foundation.
  */
 
-#include <linux/of_gpio.h>
-
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_panel.h>
 #include "drm.h"
@@ -59,10 +57,17 @@ tegra_output_connector_detect(struct drm_connector *connector, bool force)
 	enum drm_connector_status status = connector_status_unknown;
 
 	if (gpio_is_valid(output->hpd_gpio)) {
-		if (gpio_get_value(output->hpd_gpio) == 0)
-			status = connector_status_disconnected;
-		else
-			status = connector_status_connected;
+		if (output->hpd_gpio_flags & OF_GPIO_ACTIVE_LOW) {
+			if (gpio_get_value(output->hpd_gpio) != 0)
+				status = connector_status_disconnected;
+			else
+				status = connector_status_connected;
+		} else {
+			if (gpio_get_value(output->hpd_gpio) == 0)
+				status = connector_status_disconnected;
+			else
+				status = connector_status_connected;
+		}
 	} else {
 		if (!output->panel)
 			status = connector_status_disconnected;
@@ -97,7 +102,6 @@ static irqreturn_t hpd_irq(int irq, void *data)
 int tegra_output_probe(struct tegra_output *output)
 {
 	struct device_node *ddc, *panel;
-	enum of_gpio_flags flags;
 	int err, size;
 
 	if (!output->of_node)
@@ -128,7 +132,7 @@ int tegra_output_probe(struct tegra_output *output)
 
 	output->hpd_gpio = of_get_named_gpio_flags(output->of_node,
 						   "nvidia,hpd-gpio", 0,
-						   &flags);
+						   &output->hpd_gpio_flags);
 	if (gpio_is_valid(output->hpd_gpio)) {
 		unsigned long flags;