[PATCH v2 1/5] pinctrl: stm32: Handle RSVD pin configuration

[Antonio Borneo <antonio.borneo@foss.st.com>]

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

When a pin is assigned to a coprocessor not running Linux, the pin
should be flagged in the DT as reserved and not usable by Linux.

Add pin configuration RSVD (Reserved) and instrument the driver to
not update the mux setting.

Signed-off-by: Fabien Dessenne <fabien.dessenne@foss.st.com>
Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
---
 drivers/pinctrl/stm32/pinctrl-stm32.c | 9 +++++++++
 drivers/pinctrl/stm32/pinctrl-stm32.h | 3 ++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/pinctrl/stm32/pinctrl-stm32.c b/drivers/pinctrl/stm32/pinctrl-stm32.c
index ba49d48c3a1d1..e0c85f55557af 100644
--- a/drivers/pinctrl/stm32/pinctrl-stm32.c
+++ b/drivers/pinctrl/stm32/pinctrl-stm32.c
@@ -77,6 +77,7 @@ static const char * const stm32_gpio_functions[] = {
 	"af8", "af9", "af10",
 	"af11", "af12", "af13",
 	"af14", "af15", "analog",
+	"reserved",
 };
 
 struct stm32_pinctrl_group {
@@ -541,6 +542,9 @@ static bool stm32_pctrl_is_function_valid(struct stm32_pinctrl *pctl,
 		if (pin->pin.number != pin_num)
 			continue;
 
+		if (fnum == STM32_PIN_RSVD)
+			return true;
+
 		for (k = 0; k < STM32_CONFIG_NUM; k++) {
 			if (func->num == fnum)
 				return true;
@@ -841,6 +845,11 @@ static int stm32_pmx_set_mux(struct pinctrl_dev *pctldev,
 		return -EINVAL;
 	}
 
+	if (function == STM32_PIN_RSVD) {
+		dev_dbg(pctl->dev, "Reserved pins, skipping HW update.\n");
+		return 0;
+	}
+
 	bank = gpiochip_get_data(range->gc);
 	pin = stm32_gpio_pin(g->pin);
 
diff --git a/drivers/pinctrl/stm32/pinctrl-stm32.h b/drivers/pinctrl/stm32/pinctrl-stm32.h
index 5e5de92ddd58c..8a1c9570b078f 100644
--- a/drivers/pinctrl/stm32/pinctrl-stm32.h
+++ b/drivers/pinctrl/stm32/pinctrl-stm32.h
@@ -17,7 +17,8 @@
 #define STM32_PIN_GPIO		0
 #define STM32_PIN_AF(x)		((x) + 1)
 #define STM32_PIN_ANALOG	(STM32_PIN_AF(15) + 1)
-#define STM32_CONFIG_NUM	(STM32_PIN_ANALOG + 1)
+#define STM32_PIN_RSVD		(STM32_PIN_ANALOG + 1)
+#define STM32_CONFIG_NUM	(STM32_PIN_RSVD + 1)
 
 /*  package information */
 #define STM32MP_PKG_AA		BIT(0)
-- 
2.34.1