pinctrl: add generic board-level pinctrl driver using mux framework

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>
Signed-off-by: Linus Walleij <linusw@kernel.org>

diff --git a/drivers/pinctrl/Kconfig b/drivers/pinctrl/Kconfig
index 03f2e3ee065f4268dbd2f94a0ffecbbc4d89df20..31d698fbaa01d5fd20b4ba7c352df7c5f8b3c686 100644 (file)
--- 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 (file)
--- 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 (file)
index 0000000..da5a5ec
--- /dev/null
+++ b/drivers/pinctrl/pinctrl-generic-mux.c
@@ -0,0 +1,184 @@
+// 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");