Re: [PATCH 8/8] drm/tilcdc: panel: Add support for enable GPIO

Hello Fabio,

On 11 Jul 12:08 PM, Fabio Estevam wrote:

On Fri, Jul 11, 2014 at 11:18 AM, Ezequiel Garcia
[off-list ref] wrote:

quoted

In order to support the "enable GPIO" available in many panel devices,
this commit adds a proper devicetree binding.

By providing an enable GPIO in the devicetree, the driver can now turn
off and on the panel device, and/or the backlight device. Both the
backlight and the GPIO are optional properties.
+       panel_mod->enable_gpio = devm_gpiod_get(&pdev->dev, "enable");
+       if (IS_ERR(panel_mod->enable_gpio)) {
+               ret = PTR_ERR(panel_mod->enable_gpio);
+               if (ret != -ENOENT) {

Shouldn't this be controlled by a regulator instead? What if the panel
is powered from a PMIC output?

I'm not sure I understand how is that related. I have a New Heaven LCD panel
(NHD-4.3-480272EF-ATXL#-T) and it has a signal called "Display On/Off" that
I'm using to enable and disable the panel from a GPIO.

This is useful when switching the output from the panel to the HDMI for
instance, and turn off the display panel when the output goes to the HDMI.

Probably I'm missing something, I can't really see how regulators fit here.

Thanks!
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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