On 09/09/2016 10:10 AM, Marcel Ziswiler wrote:
Without this patch the following error will be shown:
stdio_add_devices: Video device failed (ret=-22)
As commit ec5507707a1d1e84056a6c864338f95f6118d3ca (video: tegra: Move to using simple-panel and pwm-backlight) states the Colibri T20 needs updating too which this patch finally attempts doing.
Please note that the current U-Boot implementation requires a dummy GPIO e.g. for a fixed backlight regulator to be explicitly defined in order to work unlike in the Linux kernel where this is taken care of automatically.
The binding documentation does state that the power supply is mandatory.
diff --git a/arch/arm/dts/tegra20-colibri.dts b/arch/arm/dts/tegra20-colibri.dts
- regulators {
compatible = "simple-bus";#address-cells = <1>;#size-cells = <0>;reg_dummy: regulator@0 {
Why call this a dummy? This is a real regulator that describes the power supply to the backlight. Even if there's no SW control over the power to the backlight, there is still a (fixed) power source, and this DT node represents that power source.
compatible = "regulator-fixed";reg = <0>;regulator-name = "Dummy";/* Dummy N/C */gpio = <&gpio TEGRA_GPIO(V, 7) GPIO_ACTIVE_HIGH>;
This is wrong. If that GPIO isn't actually part of the backlight, the DT should not say that it is. The gpio property is optional according to the DT binding documentation, so this shouldn't be needed.