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

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Hi,

On 10/20/2016 09:13 AM, Chen-Yu Tsai wrote:
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.

Does the bridge on your platform have an active/passive DAC, or is it a
smarter encoder chip that is capable of doing more? If so, it might be
good to have a separate DT compatible string to it, like what's done
in the patch titled:

drm: bridge: vga-dac: Add adi,adv7123 compatible string

so that we can switch to a different driver later if needed.

Thanks,
Archit


Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx>
---
 .../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) {


--
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