[PATCH v6 0/7] pinctrl: Add generic pinctrl for board-level mux chips

[PATCH v6 0/7] pinctrl: Add generic pinctrl for board-level mux chips

[Frank Li]

Add a generic pinctrl binding for board-level pinmux chips that are
controlled through the multiplexer subsystem.

On some boards, especially development boards, external mux chips are used
to switch SoC signals between different peripherals (e.g. MMC and UART).
The mux select lines are often driven by a GPIO expander over I2C,
as illustrated below:

        ┌──────┐      ┌─────┐
        │ SOC  │      │     │    ┌───────┐
        │      │      │     │───►│ MMC   │
        │      │      │ MUX │    └───────┘
        │      ├─────►│     │    ┌───────┐
        │      │      │     │───►│ UART  │
        │      │      └─────┘    └───────┘
        │      │         ▲
        │      │    ┌────┴──────────────┐
        │ I2C  ├───►│ GPIO Expander     │
        └──────┘    └───────────────────┘

Traditionally, gpio-hog is used to configure the onboard mux at boot.
However, the GPIO expander may probe later than consumer devices such as
MMC. As a result, the MUX might not be configured when the peripheral
driver probes, leading to initialization failures or data transfer errors.

Introduce a generic pinctrl binding that models the board-level MUX as a
pin control provider and builds proper device links between the MUX, its
GPIO controller, and peripheral devices. This ensures correct probe
ordering and reliable mux configuration.

The implementation leverages the standard multiplexer subsystem, which
provides broad support for onboard mux controllers and avoids the need for
per-driver custom MUX handling

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Changes in v6:
- rebase to v7.1-rc2
- remove devm_mux_control_get() change because it is not used yet.
- fixes a AI review bugs about cur_select.
- fixes missed EXPORT_SYMBOL_GPL(pinctrl_generic_to_map)
- Link to v5: https://lore.kernel.org/r/20260327-pinctrl-mux-v5-0-d4aec9d62c62@nxp.com

Changes in v5:
- add npins to pinctrl_generic_to_map()
- remove pins = kmalloc() in pinctrl_generic_to_map().
- Link to v4: https://lore.kernel.org/r/20260325-pinctrl-mux-v4-0-043c2c82e623@nxp.com

Changes in v4:
- use Conor Dooley suggest to extract funciton pinctrl_generic_pins_to_map()
- Link to v3: https://lore.kernel.org/r/20260311-pinctrl-mux-v3-0-236b1c17bf9b@nxp.com

Changes in v3:
- collect rob's review tag for binding
- extend and use pinctrl_generic_pins_function_dt_node_to_map()
- add judgement about
commit 2243a87d90b42eb38bc281957df3e57c712b5e56
"pinctrl: avoid duplicated calling enable_pinmux_setting for a pin"

which call pinmux_disable_setting() before pinmux_enable_setting() when
switch state. It is actually what wanted. Previous remove .disable() to
avoid hardware glitch when switch state.

New .release_mux() call intent just release software resource, like lock,
don't touch hardware register. No glitch involve. Comments already added

Linus Walleij:
  I hope this answer all of your questions. If I missed, let me know

- Link to v2: https://lore.kernel.org/r/20260225-pinctrl-mux-v2-0-1436a25fa454@nxp.com

Changes in v2:
- Add release_mux callback,
  test insmod/rmmod, mux_state_(de)select() called.
- Link to v1: https://lore.kernel.org/r/20260219-pinctrl-mux-v1-0-678d21637788@nxp.com

---
Frank Li (7):
      mux: add devm_mux_state_get_from_np() to get mux from child node
      dt-bindings: pinctrl: Add generic pinctrl for board-level mux chips
      pinctrl: extract pinctrl_generic_to_map() from pinctrl_generic_pins_function_dt_node_to_map()
      pinctrl: add optional .release_mux() callback
      pinctrl: add generic board-level pinctrl driver using mux framework
      arm64: dts: imx8mp-evk: add board-level mux for CAN2 and MICFIL
      arm64: dts: imx8mp-evk: add flexcan2 overlay file

 .../bindings/pinctrl/pinctrl-multiplexer.yaml      |  57 +++++++
 .../devicetree/bindings/pinctrl/pinctrl.yaml       |   2 +-
 arch/arm64/boot/dts/freescale/Makefile             |   4 +
 .../boot/dts/freescale/imx8mp-evk-flexcan2.dtso    |  15 ++
 arch/arm64/boot/dts/freescale/imx8mp-evk.dts       |  23 ++-
 drivers/mux/core.c                                 |  42 +++--
 drivers/pinctrl/Kconfig                            |   9 +
 drivers/pinctrl/Makefile                           |   1 +
 drivers/pinctrl/pinconf.h                          |  18 ++
 drivers/pinctrl/pinctrl-generic-mux.c              | 185 +++++++++++++++++++++
 drivers/pinctrl/pinctrl-generic.c                  |  95 ++++++-----
 drivers/pinctrl/pinmux.c                           |   5 +
 include/linux/mux/consumer.h                       |   8 +-
 include/linux/pinctrl/pinmux.h                     |   5 +
 14 files changed, 410 insertions(+), 59 deletions(-)
---
base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731
change-id: 20260213-pinctrl-mux-df9c5b661540

Best regards,
--
Frank Li <Frank.Li@nxp.com>

[PATCH v6 1/7] mux: add devm_mux_state_get_from_np() to get mux from child node

[Frank Li]

Add new API devm_mux_state_get_from_np() to retrieve a mux control from
a specified child device node.

Make devm_mux_state_get() call devm_mux_state_get_from_np() with a NULL
node parameter, which defaults to using the device's own of_node.

Support the following DT schema:

pinctrl@0 {
    uart-func {
            mux-state = <&mux_chip 0>;
    };

    spi-func {
            mux-state = <&mux_chip 1>;
    };
};

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change from v6
- rebase to v7.1
- change commit message to use 'devm_mux_state_get_from_np()", remove
devm_mux_control_get() change because it is not used yet.

change from v1 to v5
- none
---
 drivers/mux/core.c           | 42 ++++++++++++++++++++++++++----------------
 include/linux/mux/consumer.h |  8 +++++++-
 2 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/drivers/mux/core.c b/drivers/mux/core.c
index 23538de2c91b41ad998471d5af429cf3c6211e4e..2f01acfccf47b1a55037a29101951f4b1760d890 100644
--- a/drivers/mux/core.c
+++ b/drivers/mux/core.c
@@ -533,14 +533,16 @@ static struct mux_chip *of_find_mux_chip_by_node(struct device_node *np)
  * @state: Pointer to where the requested state is returned, or NULL when
  *         the required multiplexer states are handled by other means.
  * @optional: Whether to return NULL and silence errors when mux doesn't exist.
+ * @node: the device nodes, use dev->of_node if it is NULL.
  *
  * Return: Pointer to the mux-control on success, an ERR_PTR with a negative
  * errno on error, or NULL if optional is true and mux doesn't exist.
  */
 static struct mux_control *mux_get(struct device *dev, const char *mux_name,
-				   unsigned int *state, bool optional)
+				   unsigned int *state, bool optional,
+				   struct device_node *node)
 {
-	struct device_node *np = dev->of_node;
+	struct device_node *np = node ? node : dev->of_node;
 	struct of_phandle_args args;
 	struct mux_chip *mux_chip;
 	unsigned int controller;
@@ -635,7 +637,7 @@ static struct mux_control *mux_get(struct device *dev, const char *mux_name,
  */
 struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
 {
-	struct mux_control *mux = mux_get(dev, mux_name, NULL, false);
+	struct mux_control *mux = mux_get(dev, mux_name, NULL, false, NULL);
 
 	if (!mux)
 		return ERR_PTR(-ENOENT);
@@ -654,7 +656,7 @@ EXPORT_SYMBOL_GPL(mux_control_get);
  */
 struct mux_control *mux_control_get_optional(struct device *dev, const char *mux_name)
 {
-	return mux_get(dev, mux_name, NULL, true);
+	return mux_get(dev, mux_name, NULL, true, NULL);
 }
 EXPORT_SYMBOL_GPL(mux_control_get_optional);
 
@@ -712,11 +714,14 @@ EXPORT_SYMBOL_GPL(devm_mux_control_get);
  * @dev: The device that needs a mux-state.
  * @mux_name: The name identifying the mux-state.
  * @optional: Whether to return NULL and silence errors when mux doesn't exist.
+ * @np: the device nodes, use dev->of_node if it is NULL.
  *
  * Return: Pointer to the mux-state on success, an ERR_PTR with a negative
  * errno on error, or NULL if optional is true and mux doesn't exist.
  */
-static struct mux_state *mux_state_get(struct device *dev, const char *mux_name, bool optional)
+static struct mux_state *
+mux_state_get(struct device *dev, const char *mux_name, bool optional,
+	      struct device_node *np)
 {
 	struct mux_state *mstate;
 
@@ -724,7 +729,7 @@ static struct mux_state *mux_state_get(struct device *dev, const char *mux_name,
 	if (!mstate)
 		return ERR_PTR(-ENOMEM);
 
-	mstate->mux = mux_get(dev, mux_name, &mstate->state, optional);
+	mstate->mux = mux_get(dev, mux_name, &mstate->state, optional, np);
 	if (IS_ERR(mstate->mux)) {
 		int err = PTR_ERR(mstate->mux);
 
@@ -773,7 +778,7 @@ static void devm_mux_state_release(struct device *dev, void *res)
  * errno on error, or NULL if optional is true and mux doesn't exist.
  */
 static struct mux_state *__devm_mux_state_get(struct device *dev, const char *mux_name,
-					      bool optional,
+					      bool optional, struct device_node *np,
 					      int (*init)(struct mux_state *mstate),
 					      int (*exit)(struct mux_state *mstate))
 {
@@ -781,7 +786,7 @@ static struct mux_state *__devm_mux_state_get(struct device *dev, const char *mu
 	struct mux_state *mstate;
 	int ret;
 
-	mstate = mux_state_get(dev, mux_name, optional);
+	mstate = mux_state_get(dev, mux_name, optional, np);
 	if (IS_ERR(mstate))
 		return ERR_CAST(mstate);
 	else if (optional && !mstate)
@@ -815,20 +820,23 @@ static struct mux_state *__devm_mux_state_get(struct device *dev, const char *mu
 }
 
 /**
- * devm_mux_state_get() - Get the mux-state for a device, with resource
- *			  management.
+ * devm_mux_state_get_from_np() - Get the mux-state for a device, with resource
+ *				  management.
  * @dev: The device that needs a mux-control.
  * @mux_name: The name identifying the mux-control.
+ * @np: the device nodes, use dev->of_node if it is NULL.
  *
  * Return: Pointer to the mux-state, or an ERR_PTR with a negative errno.
  *
  * The mux-state will automatically be freed on release.
  */
-struct mux_state *devm_mux_state_get(struct device *dev, const char *mux_name)
+struct mux_state *
+devm_mux_state_get_from_np(struct device *dev, const char *mux_name,
+			   struct device_node *np)
 {
-	return __devm_mux_state_get(dev, mux_name, false, NULL, NULL);
+	return __devm_mux_state_get(dev, mux_name, false, np, NULL, NULL);
 }
-EXPORT_SYMBOL_GPL(devm_mux_state_get);
+EXPORT_SYMBOL_GPL(devm_mux_state_get_from_np);
 
 /**
  * devm_mux_state_get_optional() - Get the optional mux-state for a device,
@@ -843,7 +851,7 @@ EXPORT_SYMBOL_GPL(devm_mux_state_get);
  */
 struct mux_state *devm_mux_state_get_optional(struct device *dev, const char *mux_name)
 {
-	return __devm_mux_state_get(dev, mux_name, true, NULL, NULL);
+	return __devm_mux_state_get(dev, mux_name, true, NULL, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(devm_mux_state_get_optional);
 
@@ -861,7 +869,8 @@ EXPORT_SYMBOL_GPL(devm_mux_state_get_optional);
  */
 struct mux_state *devm_mux_state_get_selected(struct device *dev, const char *mux_name)
 {
-	return __devm_mux_state_get(dev, mux_name, false, mux_state_select, mux_state_deselect);
+	return __devm_mux_state_get(dev, mux_name, false, NULL,
+				    mux_state_select, mux_state_deselect);
 }
 EXPORT_SYMBOL_GPL(devm_mux_state_get_selected);
 
@@ -881,7 +890,8 @@ EXPORT_SYMBOL_GPL(devm_mux_state_get_selected);
 struct mux_state *devm_mux_state_get_optional_selected(struct device *dev,
 						       const char *mux_name)
 {
-	return __devm_mux_state_get(dev, mux_name, true, mux_state_select, mux_state_deselect);
+	return __devm_mux_state_get(dev, mux_name, true, NULL,
+				    mux_state_select, mux_state_deselect);
 }
 EXPORT_SYMBOL_GPL(devm_mux_state_get_optional_selected);
 
diff --git a/include/linux/mux/consumer.h b/include/linux/mux/consumer.h
index a961861a503b33a3ea18aee6a2eb044866aa8801..449e38e6e2c515b3dd2b51a8b8cf0295a2520804 100644
--- a/include/linux/mux/consumer.h
+++ b/include/linux/mux/consumer.h
@@ -60,7 +60,10 @@ struct mux_control *mux_control_get_optional(struct device *dev, const char *mux
 void mux_control_put(struct mux_control *mux);
 
 struct mux_control *devm_mux_control_get(struct device *dev, const char *mux_name);
-struct mux_state *devm_mux_state_get(struct device *dev, const char *mux_name);
+
+struct mux_state *
+devm_mux_state_get_from_np(struct device *dev, const char *mux_name, struct device_node *np);
+
 struct mux_state *devm_mux_state_get_optional(struct device *dev, const char *mux_name);
 struct mux_state *devm_mux_state_get_selected(struct device *dev, const char *mux_name);
 struct mux_state *devm_mux_state_get_optional_selected(struct device *dev, const char *mux_name);
@@ -161,4 +164,7 @@ static inline struct mux_state *devm_mux_state_get_optional_selected(struct devi
 
 #endif /* CONFIG_MULTIPLEXER */
 
+#define devm_mux_state_get(dev, mux_name)		\
+	devm_mux_state_get_from_np(dev, mux_name, NULL)
+
 #endif /* _LINUX_MUX_CONSUMER_H */

-- 
2.43.0

[PATCH v6 2/7] dt-bindings: pinctrl: Add generic pinctrl for board-level mux chips

[Frank Li]

Add a generic pinctrl binding for board-level pinmux chips that are
controlled through the multiplexer subsystem.

On some boards, especially development boards, external mux chips are used
to switch SoC signals between different peripherals (e.g. MMC and UART).
The mux select lines are often driven by a GPIO expander over I2C,
as illustrated below:

	┌──────┐      ┌─────┐
	│ SOC  │      │     │    ┌───────┐
	│      │      │     │───►│ MMC   │
	│      │      │ MUX │    └───────┘
	│      ├─────►│     │    ┌───────┐
	│      │      │     │───►│ UART  │
	│      │      └─────┘    └───────┘
	│      │         ▲
	│      │    ┌────┴──────────────┐
	│ I2C  ├───►│ GPIO Expander     │
	└──────┘    └───────────────────┘

Traditionally, gpio-hog is used to configure the onboard mux at boot.
However, the GPIO expander may probe later than consumer devices such as
MMC. As a result, the MUX might not be configured when the peripheral
driver probes, leading to initialization failures or data transfer errors.

Introduce a generic pinctrl binding that models the board-level MUX as a
pin control provider and builds proper device links between the MUX, its
GPIO controller, and peripheral devices. This ensures correct probe
ordering and reliable mux configuration.

The implementation leverages the standard multiplexer subsystem, which
provides broad support for onboard mux controllers and avoids the need for
per-driver custom MUX handling.

Allow pinctrl-* pattern as node name because this pinctrl device have not
reg property.

Reviewed-by: Linus Walleij <linusw@kernel.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Change in v4
- add Linus Walleij's review by tags

change in v3:
- collect rob's reviewed-by tag.

change in v2:
 - change descriptions for device, not for driver
 - add missed additionalProperties: false
---
 .../bindings/pinctrl/pinctrl-multiplexer.yaml      | 57 ++++++++++++++++++++++
 .../devicetree/bindings/pinctrl/pinctrl.yaml       |  2 +-
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-multiplexer.yaml b/Documentation/devicetree/bindings/pinctrl/pinctrl-multiplexer.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..2b0385ed879b70b24ca9c39b098c3840d08d7482
--- /dev/null
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-multiplexer.yaml
@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pinctrl/pinctrl-multiplexer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic pinctrl device for on-board MUX Chips
+
+maintainers:
+  - Frank Li <Frank.Li@nxp.com>
+
+description:
+  Generic pinctrl device for on-board MUX Chips, which switch SoC signals
+  between different peripherals (e.g. MMC and UART).
+
+  The MUX select lines are often driven by a I2C GPIO expander.
+
+properties:
+  compatible:
+    const: pinctrl-multiplexer
+
+patternProperties:
+  '-grp$':
+    type: object
+    additionalProperties: false
+    properties:
+      mux-states:
+        maxItems: 1
+
+    required:
+      - mux-states
+
+required:
+  - compatible
+
+allOf:
+  - $ref: pinctrl.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    pinctrl-mux {
+        compatible = "pinctrl-multiplexer";
+
+        uart-grp {
+            mux-states = <&mux 0>;
+        };
+
+        spi-grp {
+            mux-states = <&mux 1>;
+        };
+
+        i2c-grp {
+            mux-states = <&mux 2>;
+        };
+    };
diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl.yaml b/Documentation/devicetree/bindings/pinctrl/pinctrl.yaml
index 290438826c507ec6725f486d18cf686aa7c35e67..20176bf3074757de30f208e69b968a6bd6125273 100644
--- a/Documentation/devicetree/bindings/pinctrl/pinctrl.yaml
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl.yaml
@@ -27,7 +27,7 @@ description: |
 
 properties:
   $nodename:
-    pattern: "^(pinctrl|pinmux)(@[0-9a-f]+)?$"
+    pattern: "^(pinctrl|pinmux)(@[0-9a-f]+|-[a-z0-9]+)?$"
 
   "#pinctrl-cells":
     description: >

-- 
2.43.0

[PATCH v6 3/7] pinctrl: extract pinctrl_generic_to_map() from pinctrl_generic_pins_function_dt_node_to_map()

[Frank Li]

Refactor pinctrl_generic_pins_function_dt_subnode_to_map() by separating DT
parsing logic from map creation. Introduce a new helper
pinctrl_generic_to_map() to handle mapping to kernel data structures, while
keeping DT property parsing in the subnode function.

Improve code structure and enables easier reuse for platforms using
different DT properties (e.g. pinmux) without modifying the
dt_node_to_map-style callback API. Avoid unnecessary coupling to
pinctrl_generic_pins_function_dt_node_to_map(), which provides
functionality not needed when the phandle target is unambiguous.

Maximize code reuse and provide a cleaner extension point for future
pinctrl drivers.

Suggested-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v6:
- add missed EXPORT_SYMBOL_GPL(pinctrl_generic_to_map);

change in v5
- add npins in pinctrl_generic_to_map();
- remove below line in pinctrl_generic_to_map();
pins = devm_kcalloc(dev, npins, sizeof(*pins), GFP_KERNEL);

change in v4
- new patch
---
 drivers/pinctrl/pinconf.h         | 18 ++++++++
 drivers/pinctrl/pinctrl-generic.c | 95 +++++++++++++++++++++++----------------
 2 files changed, 74 insertions(+), 39 deletions(-)

diff --git a/drivers/pinctrl/pinconf.h b/drivers/pinctrl/pinconf.h
index 659a781e20911db4b27c7c3663c31fbbbf57c521..fa8fb0d290d1d97ba9e19d6a341a9b14c485e08e 100644
--- a/drivers/pinctrl/pinconf.h
+++ b/drivers/pinctrl/pinconf.h
@@ -172,6 +172,13 @@ int pinctrl_generic_pins_function_dt_node_to_map(struct pinctrl_dev *pctldev,
 						 struct device_node *np,
 						 struct pinctrl_map **maps,
 						 unsigned int *num_maps);
+
+int pinctrl_generic_to_map(struct pinctrl_dev *pctldev, struct device_node *parent,
+			   struct device_node *np, struct pinctrl_map **maps,
+			   unsigned int *num_maps, unsigned int *num_reserved_maps,
+			   const char **group_name, unsigned int ngroups,
+			   const char **functions, unsigned int *pins,
+			   unsigned int npins);
 #else
 static inline int
 pinctrl_generic_pins_function_dt_node_to_map(struct pinctrl_dev *pctldev,
@@ -181,4 +188,15 @@ pinctrl_generic_pins_function_dt_node_to_map(struct pinctrl_dev *pctldev,
 {
 	return -ENOTSUPP;
 }
+
+static inline int
+pinctrl_generic_to_map(struct pinctrl_dev *pctldev, struct device_node *parent,
+		       struct device_node *np, struct pinctrl_map **maps,
+		       unsigned int *num_maps, unsigned int *num_reserved_maps,
+		       const char **group_name, unsigned int ngroups,
+		       const char **functions, unsigned int *pins,
+		       void *function_data)
+{
+	return -ENOTSUPP;
+}
 #endif
diff --git a/drivers/pinctrl/pinctrl-generic.c b/drivers/pinctrl/pinctrl-generic.c
index efb39c6a670331775855efdc8566102b5c6202ef..e4cd16ce2bda379ab0933acda782d02ba1ed2e1c 100644
--- a/drivers/pinctrl/pinctrl-generic.c
+++ b/drivers/pinctrl/pinctrl-generic.c
@@ -17,29 +17,18 @@
 #include "pinctrl-utils.h"
 #include "pinmux.h"
 
-static int pinctrl_generic_pins_function_dt_subnode_to_map(struct pinctrl_dev *pctldev,
-							   struct device_node *parent,
-							   struct device_node *np,
-							   struct pinctrl_map **maps,
-							   unsigned int *num_maps,
-							   unsigned int *num_reserved_maps,
-							   const char **group_names,
-							   unsigned int ngroups)
+int pinctrl_generic_to_map(struct pinctrl_dev *pctldev, struct device_node *parent,
+			   struct device_node *np, struct pinctrl_map **maps,
+			   unsigned int *num_maps, unsigned int *num_reserved_maps,
+			   const char **group_names, unsigned int ngroups,
+			   const char **functions, unsigned int *pins,
+			   unsigned int npins)
 {
 	struct device *dev = pctldev->dev;
-	const char **functions;
+	unsigned int num_configs;
 	const char *group_name;
 	unsigned long *configs;
-	unsigned int num_configs, pin, *pins;
-	int npins, ret, reserve = 1;
-
-	npins = of_property_count_u32_elems(np, "pins");
-
-	if (npins < 1) {
-		dev_err(dev, "invalid pinctrl group %pOFn.%pOFn %d\n",
-			parent, np, npins);
-		return npins;
-	}
+	int ret, reserve = 1;
 
 	group_name = devm_kasprintf(dev, GFP_KERNEL, "%pOFn.%pOFn", parent, np);
 	if (!group_name)
@@ -47,26 +36,6 @@ static int pinctrl_generic_pins_function_dt_subnode_to_map(struct pinctrl_dev *p
 
 	group_names[ngroups] = group_name;
 
-	pins = devm_kcalloc(dev, npins, sizeof(*pins), GFP_KERNEL);
-	if (!pins)
-		return -ENOMEM;
-
-	functions = devm_kcalloc(dev, npins, sizeof(*functions), GFP_KERNEL);
-	if (!functions)
-		return -ENOMEM;
-
-	for (int i = 0; i < npins; i++) {
-		ret = of_property_read_u32_index(np, "pins", i, &pin);
-		if (ret)
-			return ret;
-
-		pins[i] = pin;
-
-		ret = of_property_read_string(np, "function", &functions[i]);
-		if (ret)
-			return ret;
-	}
-
 	ret = pinctrl_utils_reserve_map(pctldev, maps, num_reserved_maps, num_maps, reserve);
 	if (ret)
 		return ret;
@@ -102,6 +71,54 @@ static int pinctrl_generic_pins_function_dt_subnode_to_map(struct pinctrl_dev *p
 
 	return 0;
 };
+EXPORT_SYMBOL_GPL(pinctrl_generic_to_map);
+
+static int pinctrl_generic_pins_function_dt_subnode_to_map(struct pinctrl_dev *pctldev,
+							   struct device_node *parent,
+							   struct device_node *np,
+							   struct pinctrl_map **maps,
+							   unsigned int *num_maps,
+							   unsigned int *num_reserved_maps,
+							   const char **group_names,
+							   unsigned int ngroups)
+{
+	struct device *dev = pctldev->dev;
+	unsigned int pin, *pins;
+	const char **functions;
+	int npins, ret;
+
+	npins = of_property_count_u32_elems(np, "pins");
+
+	if (npins < 1) {
+		dev_err(dev, "invalid pinctrl group %pOFn.%pOFn %d\n",
+			parent, np, npins);
+		return npins;
+	}
+
+	pins = devm_kcalloc(dev, npins, sizeof(*pins), GFP_KERNEL);
+	if (!pins)
+		return -ENOMEM;
+
+	functions = devm_kcalloc(dev, npins, sizeof(*functions), GFP_KERNEL);
+	if (!functions)
+		return -ENOMEM;
+
+	for (int i = 0; i < npins; i++) {
+		ret = of_property_read_u32_index(np, "pins", i, &pin);
+		if (ret)
+			return ret;
+
+		pins[i] = pin;
+
+		ret = of_property_read_string(np, "function", &functions[i]);
+		if (ret)
+			return ret;
+	}
+
+	return pinctrl_generic_to_map(pctldev, parent, np, maps, num_maps,
+				      num_reserved_maps, group_names, ngroups,
+				      functions, pins, npins);
+}
 
 /*
  * For platforms that do not define groups or functions in the driver, but

-- 
2.43.0

[PATCH v6 4/7] pinctrl: add optional .release_mux() callback

[Frank Li]

Add an optional .release_mux() callback to struct pinmux_ops.

Some drivers acquire additional resources in .set_mux(), such as software
locks. These resources may need to be released when the mux function is no
longer active. Introducing a dedicated .release_mux() callback allows
drivers to clean up such resources.

The callback is optional and does not affect existing drivers.

Commit 2243a87d90b42 ("pinctrl: avoid duplicated calling
enable_pinmux_setting for a pin") removed the .disable() callback
to resolve two issues:

  1. desc->mux_usecount increasing monotonically
  2. Hardware glitches caused by repeated .disable()/.enable() calls

Adding .release_mux() does not reintroduce those problems. The callback is
intended only for releasing driver-side resources (e.g. locks) and must not
modify hardware registers.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v4
- none

change in v3
- Add judgement about 2243a87d90b42 ("pinctrl: avoid duplicated calling
enable_pinmux_setting for a pin") in commit message.
---
 drivers/pinctrl/pinmux.c       | 5 +++++
 include/linux/pinctrl/pinmux.h | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 3a8dd184ba3d670e01a890427e19af59b65eb813..c705bc182266c596c4e6c820f5e3ffcadbbb2838 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -517,6 +517,7 @@ void pinmux_disable_setting(const struct pinctrl_setting *setting)
 {
 	struct pinctrl_dev *pctldev = setting->pctldev;
 	const struct pinctrl_ops *pctlops = pctldev->desc->pctlops;
+	const struct pinmux_ops *ops = pctldev->desc->pmxops;
 	int ret = 0;
 	const unsigned int *pins = NULL;
 	unsigned int num_pins = 0;
@@ -563,6 +564,10 @@ void pinmux_disable_setting(const struct pinctrl_setting *setting)
 				 pins[i], desc->name, gname);
 		}
 	}
+
+	if (ops->release_mux)
+		ops->release_mux(pctldev, setting->data.mux.func,
+				 setting->data.mux.group);
 }
 
 #ifdef CONFIG_DEBUG_FS
diff --git a/include/linux/pinctrl/pinmux.h b/include/linux/pinctrl/pinmux.h
index 094bbe2fd6fd5ea3c5fdf5b6d6d9a7639700b50b..77664937eeb273eef440988c4cf833dbc6f10758 100644
--- a/include/linux/pinctrl/pinmux.h
+++ b/include/linux/pinctrl/pinmux.h
@@ -51,6 +51,8 @@ struct pinctrl_gpio_range;
  *	are handled by the pinmux subsystem. The @func_selector selects a
  *	certain function whereas @group_selector selects a certain set of pins
  *	to be used. On simple controllers the latter argument may be ignored
+ * @release_mux: Release software resources acquired by @set_mux. This callback
+ *	must not change hardware state to avoid glitches when switching mux.
  * @gpio_request_enable: requests and enables GPIO on a certain pin.
  *	Implement this only if you can mux every pin individually as GPIO. The
  *	affected GPIO range is passed along with an offset(pin number) into that
@@ -80,6 +82,9 @@ struct pinmux_ops {
 				  unsigned int selector);
 	int (*set_mux) (struct pinctrl_dev *pctldev, unsigned int func_selector,
 			unsigned int group_selector);
+	void (*release_mux) (struct pinctrl_dev *pctldev,
+			     unsigned int func_selector,
+			     unsigned int group_selector);
 	int (*gpio_request_enable) (struct pinctrl_dev *pctldev,
 				    struct pinctrl_gpio_range *range,
 				    unsigned int offset);

-- 
2.43.0

[PATCH v6 5/7] pinctrl: add generic board-level pinctrl driver using mux framework

[Frank Li]

Many boards use on-board mux chips (often controlled by GPIOs from an I2C
expander) to switch shared signals between peripherals.

Add a generic pinctrl driver built on top of the mux framework to
centralize mux handling and avoid probe ordering issues. Keep board-level
routing out of individual drivers and supports boot-time only mux
selection.

Ensure correct probe ordering, especially when the GPIO expander is probed
later.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v6:
- remove cur sel logic and depend on mux_state_select() since AI review
find a problem
https://sashiko.dev/#/patchset/20260327-pinctrl-mux-v5-0-d4aec9d62c62%40nxp.com

chagne in v4:
- use new pinctrl_generic_pins_to_map()

change in v3:
- use pinctrl_generic_pins_function_dt_node_to_map() and
pinctrl_utils_free_map().

change in v2:
- fix copywrite by add nxp
- fix if (!*map) check
- add release_mux to call mux_state_deselect()
---
 drivers/pinctrl/Kconfig               |   9 ++
 drivers/pinctrl/Makefile              |   1 +
 drivers/pinctrl/pinctrl-generic-mux.c | 185 ++++++++++++++++++++++++++++++++++
 3 files changed, 195 insertions(+)

diff --git a/drivers/pinctrl/Kconfig b/drivers/pinctrl/Kconfig
index 03f2e3ee065f4268dbd2f94a0ffecbbc4d89df20..31d698fbaa01d5fd20b4ba7c352df7c5f8b3c686 100644
--- a/drivers/pinctrl/Kconfig
+++ b/drivers/pinctrl/Kconfig
@@ -272,6 +272,15 @@ config PINCTRL_GEMINI
 	select GENERIC_PINCONF
 	select MFD_SYSCON
 
+config PINCTRL_GENERIC_MUX
+	tristate "Generic Pinctrl driver by using multiplexer"
+	depends on MULTIPLEXER
+	select PINMUX
+	select GENERIC_PINCTRL
+	help
+          Generic pinctrl driver by MULTIPLEXER framework to control on
+          board pin selection.
+
 config PINCTRL_INGENIC
 	bool "Pinctrl driver for the Ingenic JZ47xx SoCs"
 	default MACH_INGENIC
diff --git a/drivers/pinctrl/Makefile b/drivers/pinctrl/Makefile
index f7d5d5f76d0c8becc0aa1d77c68b6ced924ea264..fcd1703440d24579636e8ddb6cbd83a0a982dfb7 100644
--- a/drivers/pinctrl/Makefile
+++ b/drivers/pinctrl/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_PINCTRL_EQUILIBRIUM)   += pinctrl-equilibrium.o
 obj-$(CONFIG_PINCTRL_EP93XX)	+= pinctrl-ep93xx.o
 obj-$(CONFIG_PINCTRL_EYEQ5)	+= pinctrl-eyeq5.o
 obj-$(CONFIG_PINCTRL_GEMINI)	+= pinctrl-gemini.o
+obj-$(CONFIG_PINCTRL_GENERIC_MUX) += pinctrl-generic-mux.o
 obj-$(CONFIG_PINCTRL_INGENIC)	+= pinctrl-ingenic.o
 obj-$(CONFIG_PINCTRL_K210)	+= pinctrl-k210.o
 obj-$(CONFIG_PINCTRL_K230)	+= pinctrl-k230.o
diff --git a/drivers/pinctrl/pinctrl-generic-mux.c b/drivers/pinctrl/pinctrl-generic-mux.c
new file mode 100644
index 0000000000000000000000000000000000000000..c706468289fa179d28eca854a8818b3bf1bc5b0a
--- /dev/null
+++ b/drivers/pinctrl/pinctrl-generic-mux.c
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic Pin Control Driver for Board-Level Mux Chips
+ * Copyright 2026 NXP
+ */
+
+#include <linux/cleanup.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/mutex.h>
+#include <linux/mux/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/pinctrl/pinconf-generic.h>
+#include <linux/pinctrl/pinctrl.h>
+#include <linux/pinctrl/pinmux.h>
+#include <linux/slab.h>
+
+#include "core.h"
+#include "pinconf.h"
+#include "pinmux.h"
+#include "pinctrl-utils.h"
+
+struct mux_pin_function {
+	struct mux_state *mux_state;
+};
+
+struct mux_pinctrl {
+	struct device *dev;
+	struct pinctrl_dev *pctl;
+
+	/* mutex protect [pinctrl|pinmux]_generic functions */
+	struct mutex lock;
+};
+
+static int
+mux_pinmux_dt_node_to_map(struct pinctrl_dev *pctldev,
+			  struct device_node *np_config,
+			  struct pinctrl_map **maps, unsigned int *num_maps)
+{
+	unsigned int num_reserved_maps = 0;
+	struct mux_pin_function *function;
+	const char **group_names;
+	int ret;
+
+	function = devm_kzalloc(pctldev->dev, sizeof(*function), GFP_KERNEL);
+	if (!function)
+		return -ENOMEM;
+
+	group_names = devm_kcalloc(pctldev->dev, 1, sizeof(*group_names), GFP_KERNEL);
+	if (!group_names)
+		return -ENOMEM;
+
+	function->mux_state = devm_mux_state_get_from_np(pctldev->dev, NULL, np_config);
+	if (IS_ERR(function->mux_state))
+		return PTR_ERR(function->mux_state);
+
+	ret = pinctrl_generic_to_map(pctldev, np_config, np_config, maps,
+				     num_maps, &num_reserved_maps, group_names,
+				     0, &np_config->name, NULL, 0);
+
+	if (ret)
+		return ret;
+
+	ret = pinmux_generic_add_function(pctldev, np_config->name, group_names,
+					  1, function);
+	if (ret < 0) {
+		pinctrl_utils_free_map(pctldev, *maps, *num_maps);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct pinctrl_ops mux_pinctrl_ops = {
+	.get_groups_count = pinctrl_generic_get_group_count,
+	.get_group_name = pinctrl_generic_get_group_name,
+	.get_group_pins = pinctrl_generic_get_group_pins,
+	.dt_node_to_map = mux_pinmux_dt_node_to_map,
+	.dt_free_map = pinctrl_utils_free_map,
+};
+
+static int mux_pinmux_set_mux(struct pinctrl_dev *pctldev,
+			      unsigned int func_selector,
+			      unsigned int group_selector)
+{
+	struct mux_pinctrl *mpctl = pinctrl_dev_get_drvdata(pctldev);
+	const struct function_desc *function;
+	struct mux_pin_function *func;
+	int ret;
+
+	guard(mutex)(&mpctl->lock);
+
+	function = pinmux_generic_get_function(pctldev, func_selector);
+	func = function->data;
+
+	ret = mux_state_select(func->mux_state);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void mux_pinmux_release_mux(struct pinctrl_dev *pctldev,
+				   unsigned int func_selector,
+				   unsigned int group_selector)
+{
+	struct mux_pinctrl *mpctl = pinctrl_dev_get_drvdata(pctldev);
+	const struct function_desc *function;
+	struct mux_pin_function *func;
+
+	guard(mutex)(&mpctl->lock);
+
+	function = pinmux_generic_get_function(pctldev, func_selector);
+	func = function->data;
+
+	mux_state_deselect(func->mux_state);
+}
+
+static const struct pinmux_ops mux_pinmux_ops = {
+	.get_functions_count = pinmux_generic_get_function_count,
+	.get_function_name = pinmux_generic_get_function_name,
+	.get_function_groups = pinmux_generic_get_function_groups,
+	.set_mux = mux_pinmux_set_mux,
+	.release_mux = mux_pinmux_release_mux,
+};
+
+static int mux_pinctrl_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mux_pinctrl *mpctl;
+	struct pinctrl_desc *pctl_desc;
+	int ret;
+
+	mpctl = devm_kzalloc(dev, sizeof(*mpctl), GFP_KERNEL);
+	if (!mpctl)
+		return -ENOMEM;
+
+	mpctl->dev = dev;
+
+	platform_set_drvdata(pdev, mpctl);
+
+	pctl_desc = devm_kzalloc(dev, sizeof(*pctl_desc), GFP_KERNEL);
+	if (!pctl_desc)
+		return -ENOMEM;
+
+	ret = devm_mutex_init(dev, &mpctl->lock);
+	if (ret)
+		return ret;
+
+	pctl_desc->name = dev_name(dev);
+	pctl_desc->owner = THIS_MODULE;
+	pctl_desc->pctlops = &mux_pinctrl_ops;
+	pctl_desc->pmxops = &mux_pinmux_ops;
+
+	ret = devm_pinctrl_register_and_init(dev, pctl_desc, mpctl,
+					     &mpctl->pctl);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register pinctrl.\n");
+
+	ret = pinctrl_enable(mpctl->pctl);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable pinctrl.\n");
+
+	return 0;
+}
+
+static const struct of_device_id mux_pinctrl_of_match[] = {
+	{ .compatible = "pinctrl-multiplexer" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mux_pinctrl_of_match);
+
+static struct platform_driver mux_pinctrl_driver = {
+	.driver = {
+		.name = "generic-pinctrl-mux",
+		.of_match_table = mux_pinctrl_of_match,
+	},
+	.probe = mux_pinctrl_probe,
+};
+module_platform_driver(mux_pinctrl_driver);
+
+MODULE_AUTHOR("Frank Li <Frank.Li@nxp.com>");
+MODULE_DESCRIPTION("Generic Pin Control Driver for Board-Level Mux Chips");
+MODULE_LICENSE("GPL");
+

-- 
2.43.0

[PATCH v6 6/7] arm64: dts: imx8mp-evk: add board-level mux for CAN2 and MICFIL

[Frank Li]

The board integrates an on-board mux to route shared signals to either
CAN2 or PDM (MICFIL). The mux is controlled by a GPIO.

Add a pinctrl-based multiplexer node to describe this routing and ensure
proper probe ordering of the dependent devices.

Previously, MICFIL operation implicitly depended on the default level of
PCA6416 GPIO3. After adding the pinctrl-multiplexer, make the dependency
explicit.

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v3 - v4
- none
change in v2
- update commit message to show why need update PDM MICIFL.
---
 arch/arm64/boot/dts/freescale/imx8mp-evk.dts | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8mp-evk.dts b/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
index d0a2bd975a18138f6fc31199d2d5f0dc8149946d..f9d248121537eee64ee0042fd86f1c929ea36c83 100644
--- a/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
+++ b/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
@@ -50,6 +50,25 @@ status {
 		};
 	};
 
+	can_mux: mux-controller-0 {
+		compatible = "gpio-mux";
+		#mux-control-cells = <0>;
+		#mux-state-cells = <1>;
+		mux-gpios = <&pca6416 3 GPIO_ACTIVE_HIGH>;
+	};
+
+	can_mux_pinctrl: pinctrl-gpiomux {
+		compatible = "pinctrl-multiplexer";
+
+		can_fun: can-grp {
+			mux-states = <&can_mux 1>;
+		};
+
+		pdm_fun: pdm-grp {
+			mux-states = <&can_mux 0>;
+		};
+	};
+
 	memory@40000000 {
 		device_type = "memory";
 		reg = <0x0 0x40000000 0 0xc0000000>,
@@ -453,7 +472,7 @@ &flexcan1 {
 
 &flexcan2 {
 	pinctrl-names = "default";
-	pinctrl-0 = <&pinctrl_flexcan2>;
+	pinctrl-0 = <&pinctrl_flexcan2>, <&can_fun>;
 	phys = <&flexcan_phy 1>;
 	status = "disabled";/* can2 pin conflict with pdm */
 };
@@ -720,7 +739,7 @@ &lcdif3 {
 &micfil {
 	#sound-dai-cells = <0>;
 	pinctrl-names = "default";
-	pinctrl-0 = <&pinctrl_pdm>;
+	pinctrl-0 = <&pinctrl_pdm>, <&pdm_fun>;
 	assigned-clocks = <&clk IMX8MP_CLK_PDM>;
 	assigned-clock-parents = <&clk IMX8MP_AUDIO_PLL1_OUT>;
 	assigned-clock-rates = <196608000>;

-- 
2.43.0

[PATCH v6 7/7] arm64: dts: imx8mp-evk: add flexcan2 overlay file

[Frank Li]

Add flexcan2 overlay file, which enable flexcan2 node and disable micfil
node.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v3-v4
- none
---
 arch/arm64/boot/dts/freescale/Makefile                 |  4 ++++
 arch/arm64/boot/dts/freescale/imx8mp-evk-flexcan2.dtso | 15 +++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/arch/arm64/boot/dts/freescale/Makefile b/arch/arm64/boot/dts/freescale/Makefile
index 711e36cc2c990317130e0d691fac619ee03d8482..76173db184f5593153591bd5d427cbac91e4ab75 100644
--- a/arch/arm64/boot/dts/freescale/Makefile
+++ b/arch/arm64/boot/dts/freescale/Makefile
@@ -246,6 +246,10 @@ dtb-$(CONFIG_ARCH_MXC) += imx8mp-dhcom-pdk3.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mp-dhcom-picoitx.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mp-edm-g-wb.dtb
 dtb-$(CONFIG_ARCH_MXC) += imx8mp-evk.dtb
+
+imx8mp-evk-flexcan2-dtbs += imx8mp-evk.dtb imx8mp-evk-flexcan2.dtbo
+dtb-$(CONFIG_ARCH_MXC) += imx8mp-evk-flexcan2.dtb
+
 dtb-$(CONFIG_ARCH_MXC) += imx8mp-frdm.dtb
 DTC_FLAGS_imx8mp-hummingboard-iiot := -@
 dtb-$(CONFIG_ARCH_MXC) += imx8mp-hummingboard-iiot.dtb
diff --git a/arch/arm64/boot/dts/freescale/imx8mp-evk-flexcan2.dtso b/arch/arm64/boot/dts/freescale/imx8mp-evk-flexcan2.dtso
new file mode 100644
index 0000000000000000000000000000000000000000..f7d2674c45f72353a20300300e98c8a1eba4a2a6
--- /dev/null
+++ b/arch/arm64/boot/dts/freescale/imx8mp-evk-flexcan2.dtso
@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Copyright 2026 NXP
+ */
+
+/dts-v1/;
+/plugin/;
+
+&flexcan2 {
+        status = "okay"; /* can2 pin conflict with pdm */
+};
+
+&micfil {
+        status = "disabled";
+};

-- 
2.43.0

Re: [PATCH v6 0/7] pinctrl: Add generic pinctrl for board-level mux chips

[Linus Walleij]

Hi Frank!

On Tue, May 5, 2026 at 1:55 AM Frank Li <Frank.Li@nxp.com> wrote:

> Add a generic pinctrl binding for board-level pinmux chips that are
> controlled through the multiplexer subsystem.
>
> On some boards, especially development boards, external mux chips are used
> to switch SoC signals between different peripherals (e.g. MMC and UART).
> The mux select lines are often driven by a GPIO expander over I2C,
> as illustrated below:
>
>         ┌──────┐      ┌─────┐
>         │ SOC  │      │     │    ┌───────┐
>         │      │      │     │───►│ MMC   │
>         │      │      │ MUX │    └───────┘
>         │      ├─────►│     │    ┌───────┐
>         │      │      │     │───►│ UART  │
>         │      │      └─────┘    └───────┘
>         │      │         ▲
>         │      │    ┌────┴──────────────┐
>         │ I2C  ├───►│ GPIO Expander     │
>         └──────┘    └───────────────────┘
>
> Traditionally, gpio-hog is used to configure the onboard mux at boot.
> However, the GPIO expander may probe later than consumer devices such as
> MMC. As a result, the MUX might not be configured when the peripheral
> driver probes, leading to initialization failures or data transfer errors.
>
> Introduce a generic pinctrl binding that models the board-level MUX as a
> pin control provider and builds proper device links between the MUX, its
> GPIO controller, and peripheral devices. This ensures correct probe
> ordering and reliable mux configuration.
>
> The implementation leverages the standard multiplexer subsystem, which
> provides broad support for onboard mux controllers and avoids the need for
> per-driver custom MUX handling
>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>

I put the pinctrl patches on an immutable branch for testing again,
if nothing explodes I will try to merge it for linux-next ASAP!

Yours,
Linus Walleij