Hi Rob,

On Wed, Oct 26, 2016 at 05:13:46PM -0500, Rob Herring wrote:

On Thu, Oct 20, 2016 at 11:43:37AM +0800, Chen-Yu Tsai wrote:

quoted

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 <redacted>
---
 .../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

This should also define the active state.

quoted

+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);

So the driver should allow either active high or low.

You mean like having a enable-active-high property? Isn't that
redundant with the GPIO flags?

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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