diff mbox series

[07/14] dt-bindings: pinctrl: qcom: Add output-enable

Message ID 20230323102605.7.I7874c00092115c45377c2a06f7f133356956686e@changeid
State New
Headers
Series Control Quad SPI pinctrl better on Qualcomm Chromebooks |

Commit Message

Doug Anderson March 23, 2023, 5:30 p.m. UTC 
  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>
---

 Documentation/devicetree/bindings/pinctrl/qcom,tlmm-common.yaml | 1 +
 1 file changed, 1 insertion(+)

Comments

Krzysztof Kozlowski March 27, 2023, 7:22 a.m. UTC | #1 
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@chromium.org>

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/pinctrl/qcom,tlmm-common.yaml b/Documentation/devicetree/bindings/pinctrl/qcom,tlmm-common.yaml
index 5a815c199642..90b7d75840c1 100644
--- a/Documentation/devicetree/bindings/pinctrl/qcom,tlmm-common.yaml
+++ b/Documentation/devicetree/bindings/pinctrl/qcom,tlmm-common.yaml
@@ -77,6 +77,7 @@  $defs:
       bias-disable: true
       input-enable: false
       output-disable: true
+      output-enable: true
       output-high: true
       output-low: true