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

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Message-Id: <20230323102605.7.I7874c00092115c45377c2a06f7f133356956686e@changeid>
Date:   Thu, 23 Mar 2023 10:30:11 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     Matthias Kaehlcke <mka@...omium.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-gpio@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-spi@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 07/14] 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@...omium.org>
---

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

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

-- 
2.40.0.348.gf938b09366-goog