On 10/25/2016 02:29 PM, Chen-Yu Tsai wrote:
On Tue, Oct 25, 2016 at 4:09 PM, Archit Taneja <architt@xxxxxxxxxxxxxx> wrote:
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.
The chip is GM7123. It is not configurable. It just takes the LCD RGB/SYNC
signals and converts them to analog. The only things you can change are
putting it into sleep mode and tweaking the output drive strength by
Is sleep mode the thing that's controlled by this gpio?
changing the external reference resistor. The latter would be a hardware
design decision. I would say this qualifies as "dumb".
Yeah, I agree. I'd want feedback from Laurent too, since he had comments
on the usage of the original dumb-vga-dac driver.
I revisited the board schematics, and the enable GPIO actually toggles
an external LDO regulator. So this might be better modeled as a regulator
supply?
If you model it as a regulator, how would you toggle the GPIO on your
platform?
Looking at the chip pin out, there is a 3.3V VDD supply needed for the
chip, so it would be good to have an optional 'power' regulator supply
anyway.
Archit
Thanks
ChenYu
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) {
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
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