[PATCH v2 1/8] drm/bridge: rgb-to-vga: Support an enable GPIO

[Chen-Yu Tsai]

Some rgb-to-vga bridges have an enable GPIO, either directly tied to
an enable pin on the bridge IC, or indirectly controlling a power
switch.

Add support for it.

Signed-off-by: Chen-Yu Tsai <wens at csie.org>
---
 .../bindings/display/bridge/dumb-vga-dac.txt       |  2 ++
 drivers/gpu/drm/bridge/dumb-vga-dac.c              | 28 ++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt 
b/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
index 003bc246a270..d3484822bf77 100644
--- a/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
+++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
@@ -16,6 +16,8 @@ graph bindings specified in 
Documentation/devicetree/bindings/graph.txt.
 - Video port 0 for RGB input
 - Video port 1 for VGA output

+Optional properties:
+- enable-gpios: GPIO pin to enable or disable the bridge

 Example
 -------
diff --git a/drivers/gpu/drm/bridge/dumb-vga-dac.c 
b/drivers/gpu/drm/bridge/dumb-vga-dac.c
index afec232185a7..b487e5e9b56d 100644
--- a/drivers/gpu/drm/bridge/dumb-vga-dac.c
+++ b/drivers/gpu/drm/bridge/dumb-vga-dac.c
@@ -10,6 +10,7 @@
  * the License, or (at your option) any later version.
  */

+#include <linux/gpio/consumer.h>
 #include <linux/module.h>
 #include <linux/of_graph.h>

@@ -23,6 +24,7 @@ struct dumb_vga {
        struct drm_connector    connector;

        struct i2c_adapter      *ddc;
+       struct gpio_desc        *enable_gpio;
 };

 static inline struct dumb_vga *
@@ -124,8 +126,26 @@ static int dumb_vga_attach(struct drm_bridge *bridge)
        return 0;
 }

+static void dumb_vga_enable(struct drm_bridge *bridge)
+{
+       struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
+
+       if (vga->enable_gpio)
+               gpiod_set_value_cansleep(vga->enable_gpio, 1);
+}
+
+static void dumb_vga_disable(struct drm_bridge *bridge)
+{
+       struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
+
+       if (vga->enable_gpio)
+               gpiod_set_value_cansleep(vga->enable_gpio, 0);
+}
+
 static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
        .attach         = dumb_vga_attach,
+       .enable         = dumb_vga_enable,
+       .disable        = dumb_vga_disable,
 };

 static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
@@ -169,6 +189,14 @@ static int dumb_vga_probe(struct platform_device *pdev)
                return -ENOMEM;
        platform_set_drvdata(pdev, vga);

+       vga->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
+                                                  GPIOD_OUT_LOW);
+       if (IS_ERR(vga->enable_gpio)) {
+               ret = PTR_ERR(vga->enable_gpio);
+               dev_err(&pdev->dev, "failed to request GPIO: %d\n", ret);
+               return ret;
+       }
+
        vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
        if (IS_ERR(vga->ddc)) {
                if (PTR_ERR(vga->ddc) == -ENODEV) {
-- 
2.9.3