On 23/03/2023 18:30, Douglas Anderson wrote:
> In the patch ("dt-bindings: pinctrl: qcom: tlmm should use
> output-disable, not input-enable") we allowed setting "output-disable"
> for TLMM pinctrl states. Let's also add "output-enable".
>
> At first blush this seems a needless thing to do. Specifically:
> - In Linux (and presumably any other OSes using the same device trees)
> the GPIO/pinctrl driver knows to automatically enable the output
> when a GPIO is changed to an output. Thus in most cases specifying
> "output-enable" is superfluous and should be avoided.
> - If we need to set a pin's default state we already have
> "output-high" and "output-low" and these properties already imply
> "output-enabled" (at least on the Linux Qualcomm TLMM driver).
>
> However, there is one instance where "output-enable" seems like it
> could be useful: sleep states. It's not uncommon to want to configure
> pins as inputs (with appropriate pulls) when the driver controlling
> them is in a low power state. Then we want the pins back to outputs
> when the driver wants things running normally. To accomplish this we'd
> want to be able to use "output-enable". Then the "default" state could
> have "output-enable" and the "sleep" state could have
> "output-disable".
>
> NOTE: in all instances I'm aware of, we'd only want to use
> "output-enable" on pins that are configured as "gpio". The Qualcomm
> documentation that I have access to says that "output-enable" only
> does something useful when in GPIO mode.
>
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
Best regards,
Krzysztof
