[PATCH RFC 1/5] pinctrl: allow to mark pin functions as requestable GPIOs

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

The name of the pin function has no real meaning to pinctrl core and is
there only for human readability of device properties. Some pins are
muxed as GPIOs but for "strict" pinmuxers it's impossible to request
them as GPIOs if they're bound to a devide - even if their function name
explicitly says "gpio". Add a new field to struct pinfunction that
allows to pass additional flags to pinctrl core. While we could go with
a boolean "is_gpio" field, a flags field is more future-proof.

If the PINFUNCTION_FLAG_GPIO is set for a given function, the pin muxed
to it can be requested as GPIO even on strict pin controllers. Add a new
callback to struct pinmux_ops - function_is_gpio() - that allows pinmux
core to inspect a function and see if it's a GPIO one.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
---
 drivers/pinctrl/pinmux.c        | 17 +++++++++++++++--
 include/linux/pinctrl/pinctrl.h | 14 ++++++++++++++
 include/linux/pinctrl/pinmux.h  |  2 ++
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 0743190da59e819d1c72c1ed1ece72f206d60d65..49855e6c49616d70bf9c805fc7c11ef41284dc52 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -89,13 +89,19 @@ bool pinmux_can_be_used_for_gpio(struct pinctrl_dev *pctldev, unsigned int pin)
 {
 	struct pin_desc *desc = pin_desc_get(pctldev, pin);
 	const struct pinmux_ops *ops = pctldev->desc->pmxops;
+	const struct pinctrl_setting_mux *mux_setting = desc->mux_setting;
+	bool func_is_gpio = false;
 
 	/* Can't inspect pin, assume it can be used */
 	if (!desc || !ops)
 		return true;
 
 	guard(mutex)(&desc->mux_lock);
-	if (ops->strict && desc->mux_usecount)
+	if (ops->function_is_gpio && mux_setting)
+		func_is_gpio = ops->function_is_gpio(pctldev,
+						     mux_setting->func);
+
+	if (ops->strict && desc->mux_usecount && !func_is_gpio)
 		return false;
 
 	return !(ops->strict && !!desc->gpio_owner);
@@ -116,7 +122,9 @@ static int pin_request(struct pinctrl_dev *pctldev,
 {
 	struct pin_desc *desc;
 	const struct pinmux_ops *ops = pctldev->desc->pmxops;
+	const struct pinctrl_setting_mux *mux_setting;
 	int status = -EINVAL;
+	bool func_is_gpio = false;
 
 	desc = pin_desc_get(pctldev, pin);
 	if (desc == NULL) {
@@ -126,11 +134,16 @@ static int pin_request(struct pinctrl_dev *pctldev,
 		goto out;
 	}
 
+	mux_setting = desc->mux_setting;
+
 	dev_dbg(pctldev->dev, "request pin %d (%s) for %s\n",
 		pin, desc->name, owner);
 
 	scoped_guard(mutex, &desc->mux_lock) {
-		if ((!gpio_range || ops->strict) &&
+		if (ops->function_is_gpio && mux_setting)
+			func_is_gpio = ops->function_is_gpio(pctldev,
+							     mux_setting->func);
+		if ((!gpio_range || ops->strict) && !func_is_gpio &&
 		    desc->mux_usecount && strcmp(desc->mux_owner, owner)) {
 			dev_err(pctldev->dev,
 				"pin %s already requested by %s; cannot claim for %s\n",
diff --git a/include/linux/pinctrl/pinctrl.h b/include/linux/pinctrl/pinctrl.h
index d138e18156452e008f24ca06358fcab45135632f..1a8084e2940537f8f0862761d3e47c56c8783193 100644
--- a/include/linux/pinctrl/pinctrl.h
+++ b/include/linux/pinctrl/pinctrl.h
@@ -11,6 +11,7 @@
 #ifndef __LINUX_PINCTRL_PINCTRL_H
 #define __LINUX_PINCTRL_PINCTRL_H
 
+#include <linux/bits.h>
 #include <linux/types.h>
 
 struct device;
@@ -206,16 +207,20 @@ extern int pinctrl_get_group_pins(struct pinctrl_dev *pctldev,
 				  const char *pin_group, const unsigned int **pins,
 				  unsigned int *num_pins);
 
+#define PINFUNCTION_FLAG_GPIO	BIT(0)
+
 /**
  * struct pinfunction - Description about a function
  * @name: Name of the function
  * @groups: An array of groups for this function
  * @ngroups: Number of groups in @groups
+ * @flags: Additional pin function flags
  */
 struct pinfunction {
 	const char *name;
 	const char * const *groups;
 	size_t ngroups;
+	unsigned long flags;
 };
 
 /* Convenience macro to define a single named pinfunction */
@@ -226,6 +231,15 @@ struct pinfunction {
 		.ngroups = (_ngroups),			\
 	}
 
+/* Same as PINCTRL_PINFUNCTION() but for the GPIO category of functions */
+#define PINCTRL_GPIO_PINFUNCTION(_name, _groups, _ngroups)	\
+(struct pinfunction) {						\
+		.name = (_name),				\
+		.groups = (_groups),				\
+		.ngroups = (_ngroups),				\
+		.flags = PINFUNCTION_FLAG_GPIO,			\
+	}
+
 #if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_PINCTRL)
 extern struct pinctrl_dev *of_pinctrl_get(struct device_node *np);
 #else
diff --git a/include/linux/pinctrl/pinmux.h b/include/linux/pinctrl/pinmux.h
index d6f7b58d6ad0cce421aad80463529c9ccc65d68e..6db6c3e1ccc2249d4b4204e6fc19bf7b4397cc81 100644
--- a/include/linux/pinctrl/pinmux.h
+++ b/include/linux/pinctrl/pinmux.h
@@ -66,6 +66,8 @@ struct pinmux_ops {
 				    unsigned int selector,
 				    const char * const **groups,
 				    unsigned int *num_groups);
+	bool (*function_is_gpio) (struct pinctrl_dev *pctldev,
+				  unsigned int selector);
 	int (*set_mux) (struct pinctrl_dev *pctldev, unsigned int func_selector,
 			unsigned int group_selector);
 	int (*gpio_request_enable) (struct pinctrl_dev *pctldev,

-- 
2.48.1