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>
As evidenced by the Qualcomm TLMM Linux driver, the TLMM IP block in
Qualcomm SoCs has a bit to enable/disable the output for a pin that's
configured as a GPIO but _not_ a bit to enable/disable an input
buffer. Current device trees that are specifying "input-enable" for
pins managed by TLMM are either doing so needlessly or are using it to
mean "output-disable".
Presumably the current convention of using "input-enable" to mean
"output-disable" stems from the fact that "output-disable" is a "new"
property from 2017. It was introduced in commit 425562429d
("pinctrl: generic: Add output-enable property"). The "input-enable"
handling in Qualcomm drivers is from 2015 introduced in commit
407f5e392f ("pinctrl: qcom: handle input-enable pinconf property").
Given that there's no other use for "input-enable" for TLMM, we can
still handle old device trees in code, but let's encourage people to
move to the proper / documented property by updating the bindings.
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/20230323102605.6.I291ce0ba2c6ea80b341659c4f75a567a76dd7ca6@changeid
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
