[PATCH v4 4/7] pinctrl: add optional .release_mux() callback

Frank Li
2026-03-25T23:04:46Z

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 These resources may need to be released when the mux function is no
longer active.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