linux-kernel - [PATCH v2 2/5] dt-bindings: pinctrl: stm32: Add RSVD mux function

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Message-ID: <20250610151837.299244-3-antonio.borneo@foss.st.com>
Date: Tue, 10 Jun 2025 17:18:34 +0200
From: Antonio Borneo <antonio.borneo@...s.st.com>
To: Linus Walleij <linus.walleij@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        <linux-gpio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC: Antonio Borneo <antonio.borneo@...s.st.com>,
        Maxime Coquelin
	<mcoquelin.stm32@...il.com>,
        Fabien Dessenne <fabien.dessenne@...s.st.com>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski@...aro.org>
Subject: [PATCH v2 2/5] dt-bindings: pinctrl: stm32: Add RSVD mux function

From: Fabien Dessenne <fabien.dessenne@...s.st.com>

Document the RSVD (Reserved) mux function, used to reserve pins
for a coprocessor not running Linux.

Signed-off-by: Fabien Dessenne <fabien.dessenne@...s.st.com>
Signed-off-by: Antonio Borneo <antonio.borneo@...s.st.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
---
 .../devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml     | 8 ++++++++
 include/dt-bindings/pinctrl/stm32-pinfunc.h               | 1 +
 2 files changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml b/Documentation/devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml
index a28d77748095a..5d17d6487ae9c 100644
--- a/Documentation/devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml
+++ b/Documentation/devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml
@@ -160,9 +160,13 @@ patternProperties:
               * ...
               * 16 : Alternate Function 15
               * 17 : Analog
+              * 18 : Reserved
               To simplify the usage, macro is available to generate "pinmux" field.
               This macro is available here:
                 - include/dt-bindings/pinctrl/stm32-pinfunc.h
+              Setting the pinmux's function to the Reserved (RSVD) value is used to inform
+              the driver that it shall not apply the mux setting. This can be used to
+              reserve some pins, for example to a co-processor not running Linux.
               Some examples of using macro:
                /* GPIO A9 set as alternate function 2 */
                ... {
@@ -176,6 +180,10 @@ patternProperties:
                ... {
                           pinmux = <STM32_PINMUX('A', 9, ANALOG)>;
                };
+               /* GPIO A9 reserved for co-processor */
+               ... {
+                          pinmux = <STM32_PINMUX('A', 9, RSVD)>;
+               };
 
           bias-disable:
             type: boolean
diff --git a/include/dt-bindings/pinctrl/stm32-pinfunc.h b/include/dt-bindings/pinctrl/stm32-pinfunc.h
index 28ad0235086a6..af3fd388329a0 100644
--- a/include/dt-bindings/pinctrl/stm32-pinfunc.h
+++ b/include/dt-bindings/pinctrl/stm32-pinfunc.h
@@ -26,6 +26,7 @@
 #define AF14	0xf
 #define AF15	0x10
 #define ANALOG	0x11
+#define RSVD	0x12
 
 /* define Pins number*/
 #define PIN_NO(port, line)	(((port) - 'A') * 0x10 + (line))
-- 
2.34.1