drm/exynos: dp: support hotplug detection via GPIO

Certain bridge chips use a GPIO to indicate the cable status instead
of the I_DP_HPD pin.  This adds an optional device-tree property,
"samsung,hpd-gpio", to the exynos-dp controller which indicates that
the specified GPIO should be used for hotplug detection.
The GPIO is then set up as an edge-triggered interrupt where the
rising edge indicates hotplug-in and the falling edge indicates hotplug-out.

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: Rahul Sharma <rahul.sharma@samsung.com>
Signed-off-by: Ajay Kumar <ajaykumar.rs@samsung.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

4 files changed, 66 insertions, 15 deletions

diff --git a/Documentation/devicetree/bindings/video/exynos_dp.txt b/Documentation/devicetree/bindings/video/exynos_dp.txt
index 57ccdde02c3a..53dbccfa80ca 100644
--- a/Documentation/devicetree/bindings/video/exynos_dp.txt
+++ b/Documentation/devicetree/bindings/video/exynos_dp.txt
@@ -62,6 +62,10 @@ Optional properties for dp-controller:
         -hsync-active-high:
                 HSYNC polarity configuration.
                         High if defined, Low if not defined
+        -samsung,hpd-gpio:
+                Hotplug detect GPIO.
+                        Indicates which GPIO should be used for hotplug
+                        detection
 
 Example:
 
diff --git a/drivers/gpu/drm/exynos/exynos_dp_core.c b/drivers/gpu/drm/exynos/exynos_dp_core.c
index 1f8914b44714..2b30c55ab050 100644
--- a/drivers/gpu/drm/exynos/exynos_dp_core.c
+++ b/drivers/gpu/drm/exynos/exynos_dp_core.c
@@ -18,6 +18,8 @@
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <linux/gpio.h>
 #include <linux/component.h>
 #include <linux/phy/phy.h>
 #include <video/of_display_timing.h>
@@ -1217,6 +1219,7 @@ static int exynos_dp_bind(struct device *dev, struct device *master, void *data)
         struct drm_device *drm_dev = data;
         struct resource *res;
         struct exynos_dp_device *dp;
+        unsigned int irq_flags;
 
         int ret = 0;
 
@@ -1254,7 +1257,30 @@ static int exynos_dp_bind(struct device *dev, struct device *master, void *data)
         if (IS_ERR(dp->reg_base))
                 return PTR_ERR(dp->reg_base);
 
-        dp->irq = platform_get_irq(pdev, 0);
+        dp->hpd_gpio = of_get_named_gpio(dev->of_node, "samsung,hpd-gpio", 0);
+
+        if (gpio_is_valid(dp->hpd_gpio)) {
+                /*
+                 * Set up the hotplug GPIO from the device tree as an interrupt.
+                 * Simply specifying a different interrupt in the device tree
+                 * doesn't work since we handle hotplug rather differently when
+                 * using a GPIO.  We also need the actual GPIO specifier so
+                 * that we can get the current state of the GPIO.
+                 */
+                ret = devm_gpio_request_one(&pdev->dev, dp->hpd_gpio, GPIOF_IN,
+                                            "hpd_gpio");
+                if (ret) {
+                        dev_err(&pdev->dev, "failed to get hpd gpio\n");
+                        return ret;
+                }
+                dp->irq = gpio_to_irq(dp->hpd_gpio);
+                irq_flags = IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING;
+        } else {
+                dp->hpd_gpio = -ENODEV;
+                dp->irq = platform_get_irq(pdev, 0);
+                irq_flags = 0;
+        }
+
         if (dp->irq == -ENXIO) {
                 dev_err(&pdev->dev, "failed to get irq\n");
                 return -ENODEV;
@@ -1266,8 +1292,8 @@ static int exynos_dp_bind(struct device *dev, struct device *master, void *data)
 
         exynos_dp_init_dp(dp);
 
-        ret = devm_request_irq(&pdev->dev, dp->irq, exynos_dp_irq_handler, 0,
-                                "exynos-dp", dp);
+        ret = devm_request_irq(&pdev->dev, dp->irq, exynos_dp_irq_handler,
+                        irq_flags, "exynos-dp", dp);
         if (ret) {
                 dev_err(&pdev->dev, "failed to request irq\n");
                 return ret;
diff --git a/drivers/gpu/drm/exynos/exynos_dp_core.h b/drivers/gpu/drm/exynos/exynos_dp_core.h
index d6a900d4ee40..56fa43eb7133 100644
--- a/drivers/gpu/drm/exynos/exynos_dp_core.h
+++ b/drivers/gpu/drm/exynos/exynos_dp_core.h
@@ -159,6 +159,7 @@ struct exynos_dp_device {
         struct work_struct      hotplug_work;
         struct phy              *phy;
         int                     dpms_mode;
+        int                     hpd_gpio;
 
         struct exynos_drm_panel_info panel;
 };
diff --git a/drivers/gpu/drm/exynos/exynos_dp_reg.c b/drivers/gpu/drm/exynos/exynos_dp_reg.c
index b70da5052ff0..79291a2ce50d 100644
--- a/drivers/gpu/drm/exynos/exynos_dp_reg.c
+++ b/drivers/gpu/drm/exynos/exynos_dp_reg.c
@@ -13,6 +13,7 @@
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/delay.h>
+#include <linux/gpio.h>
 
 #include "exynos_dp_core.h"
 #include "exynos_dp_reg.h"
@@ -326,6 +327,9 @@ void exynos_dp_clear_hotplug_interrupts(struct exynos_dp_device *dp)
 {
         u32 reg;
 
+        if (gpio_is_valid(dp->hpd_gpio))
+                return;
+
         reg = HOTPLUG_CHG | HPD_LOST | PLUG;
         writel(reg, dp->reg_base + EXYNOS_DP_COMMON_INT_STA_4);
 
@@ -337,6 +341,9 @@ void exynos_dp_init_hpd(struct exynos_dp_device *dp)
 {
         u32 reg;
 
+        if (gpio_is_valid(dp->hpd_gpio))
+                return;
+
         exynos_dp_clear_hotplug_interrupts(dp);
 
         reg = readl(dp->reg_base + EXYNOS_DP_SYS_CTL_3);
@@ -348,19 +355,27 @@ enum dp_irq_type exynos_dp_get_irq_type(struct exynos_dp_device *dp)
 {
         u32 reg;
 
-        /* Parse hotplug interrupt status register */
-        reg = readl(dp->reg_base + EXYNOS_DP_COMMON_INT_STA_4);
+        if (gpio_is_valid(dp->hpd_gpio)) {
+                reg = gpio_get_value(dp->hpd_gpio);
+                if (reg)
+                        return DP_IRQ_TYPE_HP_CABLE_IN;
+                else
+                        return DP_IRQ_TYPE_HP_CABLE_OUT;
+        } else {
+                /* Parse hotplug interrupt status register */
+                reg = readl(dp->reg_base + EXYNOS_DP_COMMON_INT_STA_4);
 
-        if (reg & PLUG)
-                return DP_IRQ_TYPE_HP_CABLE_IN;
+                if (reg & PLUG)
+                        return DP_IRQ_TYPE_HP_CABLE_IN;
 
-        if (reg & HPD_LOST)
-                return DP_IRQ_TYPE_HP_CABLE_OUT;
+                if (reg & HPD_LOST)
+                        return DP_IRQ_TYPE_HP_CABLE_OUT;
 
-        if (reg & HOTPLUG_CHG)
-                return DP_IRQ_TYPE_HP_CHANGE;
+                if (reg & HOTPLUG_CHG)
+                        return DP_IRQ_TYPE_HP_CHANGE;
 
-        return DP_IRQ_TYPE_UNKNOWN;
+                return DP_IRQ_TYPE_UNKNOWN;
+        }
 }
 
 void exynos_dp_reset_aux(struct exynos_dp_device *dp)
@@ -402,9 +417,14 @@ int exynos_dp_get_plug_in_status(struct exynos_dp_device *dp)
 {
         u32 reg;
 
-        reg = readl(dp->reg_base + EXYNOS_DP_SYS_CTL_3);
-        if (reg & HPD_STATUS)
-                return 0;
+        if (gpio_is_valid(dp->hpd_gpio)) {
+                if (gpio_get_value(dp->hpd_gpio))
+                        return 0;
+        } else {
+                reg = readl(dp->reg_base + EXYNOS_DP_SYS_CTL_3);
+                if (reg & HPD_STATUS)
+                        return 0;
+        }
 
         return -EINVAL;
 }