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| H A D | qcom,tlmm-common.yaml | 988a9eab Thu Mar 23 12:30:11 CDT 2023 Douglas Anderson <dianders@chromium.org> dt-bindings: pinctrl: qcom: Add output-enable
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@chromium.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230323102605.7.I7874c00092115c45377c2a06f7f133356956686e@changeid
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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