[RFC,4/5] pinctrl: Support ROHM BD79124 pinmux / GPO

diff --git a/drivers/pinctrl/Kconfig b/drivers/pinctrl/Kconfig
index 95a8e2b9a614..7dd9bb0d1ab4 100644
--- a/drivers/pinctrl/Kconfig
+++ b/drivers/pinctrl/Kconfig
@@ -145,6 +145,17 @@  config PINCTRL_AW9523
 
 	  Say yes to enable pinctrl and GPIO support for the AW9523(B).
 
+config PINCTRL_BD79124
+	tristate "Rohm BD79124 ADC/GPO"
+	depends on MFD_ROHM_BD79124
+	select PINMUX
+	select GPIOLIB
+	help
+	  The Rohm BD79124 is a 12-bit, 8-channel, SAR ADC. The analog input
+	  pins can also be configured to be used as general purpose outputs.
+
+	  Say yes to enable the pinmux and GPOs.
+
 config PINCTRL_BM1880
 	bool "Bitmain BM1880 Pinctrl driver"
 	depends on OF && (ARCH_BITMAIN || COMPILE_TEST)
diff --git a/drivers/pinctrl/Makefile b/drivers/pinctrl/Makefile
index fba1c56624c0..0caf6dc3d2c1 100644
--- a/drivers/pinctrl/Makefile
+++ b/drivers/pinctrl/Makefile
@@ -18,6 +18,7 @@  obj-$(CONFIG_PINCTRL_AT91PIO4)	+= pinctrl-at91-pio4.o
 obj-$(CONFIG_PINCTRL_AW9523)	+= pinctrl-aw9523.o
 obj-$(CONFIG_PINCTRL_AXP209)	+= pinctrl-axp209.o
 obj-$(CONFIG_PINCTRL_BM1880)	+= pinctrl-bm1880.o
+obj-$(CONFIG_PINCTRL_BD79124)	+= pinctrl-bd79124.o
 obj-$(CONFIG_PINCTRL_CY8C95X0)	+= pinctrl-cy8c95x0.o
 obj-$(CONFIG_PINCTRL_DA850_PUPD) += pinctrl-da850-pupd.o
 obj-$(CONFIG_PINCTRL_DA9062)	+= pinctrl-da9062.o
diff --git a/drivers/pinctrl/pinctrl-bd79124.c b/drivers/pinctrl/pinctrl-bd79124.c
new file mode 100644
index 000000000000..8d25b1c5345f
--- /dev/null
+++ b/drivers/pinctrl/pinctrl-bd79124.c
@@ -0,0 +1,276 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ROHM BD79124 ADC / GPO pinmux.
+ *
+ * Copyright (c) 2025, ROHM Semiconductor.
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+#include <linux/pinctrl/pinctrl.h>
+#include <linux/pinctrl/pinmux.h>
+#include <linux/mfd/rohm-bd79124.h>
+#include "pinctrl-utils.h"
+
+/*
+ * The driver expects pins top have 1 to 1 mapping to the groups.
+ * Eg, pin 'ID 0' is AIN0, and can be directly mapped to the group "ain0", which
+ * also uses group ID 0. The driver mix and match the pin and group IDs. This
+ * works because we don't have any specific multi-pin groups. If I knew typical
+ * use cases better I might've been able to create some funtionally meaningful
+ * groups - but as I don't, I just decided to create per-pin groups for toggling
+ * and individual pin to ADC-input or GPO mode. I believe this gives the
+ * flexibility for generic use-cases.
+ *
+ * If this is a false assumption and special groups are needed, then the pin <=>
+ * group mapping in this driver must be reworked. Meanwhile just keep the pin
+ * and group IDs matching!
+ */
+static const struct pinctrl_pin_desc bd79124_pins[] = {
+	PINCTRL_PIN(0, "ain0"),
+	PINCTRL_PIN(1, "ain1"),
+	PINCTRL_PIN(2, "ain2"),
+	PINCTRL_PIN(3, "ain3"),
+	PINCTRL_PIN(4, "ain4"),
+	PINCTRL_PIN(5, "ain5"),
+	PINCTRL_PIN(6, "ain6"),
+	PINCTRL_PIN(7, "ain7"),
+};
+
+static const char * const bd79124_pin_groups[] = {
+	"ain0",
+	"ain1",
+	"ain2",
+	"ain3",
+	"ain4",
+	"ain5",
+	"ain6",
+	"ain7",
+};
+
+static int bd79124_get_groups_count(struct pinctrl_dev *pcdev)
+{
+	return ARRAY_SIZE(bd79124_pin_groups);
+}
+
+static const char *bd79124_get_group_name(struct pinctrl_dev *pctldev,
+					   unsigned int group)
+{
+	return bd79124_pin_groups[group];
+}
+
+enum {
+	BD79124_FUNC_GPO,
+	BD79124_FUNC_ADC,
+	BD79124_FUNC_AMOUNT
+};
+
+static const char * const bd79124_functions[BD79124_FUNC_AMOUNT] = {
+	[BD79124_FUNC_GPO] = "gpo",
+	[BD79124_FUNC_ADC] = "adc",
+};
+
+struct bd79124_mux_data {
+	struct device *dev;
+	struct regmap *map;
+	struct pinctrl_dev *pcdev;
+	struct gpio_chip gc;
+};
+
+static int bd79124_pmx_get_functions_count(struct pinctrl_dev *pcdev)
+{
+	return BD79124_FUNC_AMOUNT;
+}
+
+static const char *bd79124_pmx_get_function_name(struct pinctrl_dev *pcdev,
+						  unsigned int selector)
+{
+	return bd79124_functions[selector];
+}
+
+static int bd79124_pmx_get_function_groups(struct pinctrl_dev *pcdev,
+		unsigned int selector,
+		const char * const **groups,
+		unsigned int * const num_groups)
+{
+	*groups = &bd79124_pin_groups[0];
+	*num_groups = ARRAY_SIZE(bd79124_pin_groups);
+
+	return 0;
+}
+
+static int bd79124_pmx_set(struct pinctrl_dev *pcdev, unsigned int func,
+			   unsigned int group)
+{
+	struct bd79124_mux_data *d = pinctrl_dev_get_drvdata(pcdev);
+
+	/* We use 1 to 1 mapping for grp <=> pin */
+	if (func == BD79124_FUNC_GPO)
+		return regmap_set_bits(d->map, BD79124_REG_PINCFG, BIT(group));
+
+	return regmap_clear_bits(d->map, BD79124_REG_PINCFG, BIT(group));
+}
+
+/*
+ * Check that the pinmux has set this pin as GPO before allowing it to be used.
+ * NOTE: There is no locking in the pinctrl driver to ensure the pin _stays_
+ * appropriately muxed. It is the responsibility of the device using this GPO
+ * (or ADC) to reserve the pin from the pinmux.
+ */
+static bool bd79124_is_gpo(struct bd79124_mux_data *d, unsigned int offset)
+{
+	int ret, val;
+
+	ret = regmap_read(d->map, BD79124_REG_PINCFG, &val);
+	/*
+	 * If read fails, don't allow setting GPO value as we don't know if
+	 * pin is used as AIN. (In which case we might upset the device being
+	 * measured - although I suppose the BD79124 would ignore the set value
+	 * if pin is used as AIN - but better safe than sorry, right?
+	 */
+	if (ret)
+		return 0;
+
+	return (val & BIT(offset));
+}
+
+static int bd79124gpo_direction_get(struct gpio_chip *gc, unsigned int offset)
+{
+	struct bd79124_mux_data *d = gpiochip_get_data(gc);
+
+	if (!bd79124_is_gpo(d, offset))
+		return -EINVAL;
+
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+static void bd79124gpo_set(struct gpio_chip *gc, unsigned int offset, int value)
+{
+	struct bd79124_mux_data *d = gpiochip_get_data(gc);
+
+	if (!bd79124_is_gpo(d, offset)) {
+		dev_dbg(d->dev, "Bad GPO mux mode\n");
+		return;
+	}
+
+	if (value)
+		regmap_set_bits(d->map, BD79124_REG_GPO_VAL, BIT(offset));
+
+	regmap_clear_bits(d->map, BD79124_REG_GPO_VAL, BIT(offset));
+}
+
+static void bd79124gpo_set_multiple(struct gpio_chip *gc, unsigned long *mask,
+				   unsigned long *bits)
+{
+	int ret, val;
+	struct bd79124_mux_data *d = gpiochip_get_data(gc);
+
+	/* Ensure all GPIOs in 'mask' are set to be GPIOs */
+	ret = regmap_read(d->map, BD79124_REG_PINCFG, &val);
+	if (ret)
+		return;
+
+	if ((val & *mask) != *mask) {
+		dev_dbg(d->dev, "Invalid mux config. Can't set value.\n");
+		/* Do not set value for pins configured as ADC inputs */
+		*mask &= val;
+	}
+
+	regmap_update_bits(d->map, BD79124_REG_GPO_VAL, *mask, *bits);
+}
+
+/* Template for GPIO chip */
+static const struct gpio_chip bd79124gpo_chip = {
+	.label			= "bd79124-gpo",
+	.get_direction		= bd79124gpo_direction_get,
+	.set			= bd79124gpo_set,
+	.set_multiple		= bd79124gpo_set_multiple,
+	.can_sleep		= true,
+	.ngpio			= 8,
+	.base			= -1,
+};
+
+static const struct pinmux_ops bd79124_pmxops = {
+	.get_functions_count = bd79124_pmx_get_functions_count,
+	.get_function_name = bd79124_pmx_get_function_name,
+	.get_function_groups = bd79124_pmx_get_function_groups,
+	.set_mux = bd79124_pmx_set,
+};
+
+static const struct pinctrl_ops bd79124_pctlops = {
+	.get_groups_count = bd79124_get_groups_count,
+	.get_group_name = bd79124_get_group_name,
+	.dt_node_to_map = pinconf_generic_dt_node_to_map_all,
+	.dt_free_map = pinctrl_utils_free_map,
+};
+
+static const struct pinctrl_desc bd79124_pdesc = {
+	.name = "bd79124-pinctrl",
+	.pins = &bd79124_pins[0],
+	.npins = ARRAY_SIZE(bd79124_pins),
+	.pmxops = &bd79124_pmxops,
+	.pctlops = &bd79124_pctlops,
+};
+
+static int bd79124_probe(struct platform_device *pdev)
+{
+	struct bd79124_mux_data *d;
+	int ret;
+
+	d = devm_kzalloc(&pdev->dev, sizeof(*d), GFP_KERNEL);
+	if (!d)
+		return -ENOMEM;
+
+	d->dev = &pdev->dev;
+	d->map = dev_get_regmap(d->dev->parent, NULL);
+	if (!d->map)
+		return dev_err_probe(d->dev, -ENODEV, "No regmap\n");
+
+	d->gc = bd79124gpo_chip;
+
+	ret = devm_pinctrl_register_and_init(d->dev->parent,
+			(struct pinctrl_desc *)&bd79124_pdesc, d, &d->pcdev);
+	if (ret)
+		return dev_err_probe(d->dev, ret, "pincontrol registration failed\n");
+	ret = pinctrl_enable(d->pcdev);
+	if (ret)
+		return dev_err_probe(d->dev, ret, "pincontrol enabling failed\n");
+
+	ret = devm_gpiochip_add_data(d->dev, &d->gc, d);
+	if (ret)
+		return dev_err_probe(d->dev, ret, "gpio init Failed\n");
+
+	return 0;
+}
+
+static const struct platform_device_id bd79124_mux_id[] = {
+	{ "bd79124-pinmux", },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, bd79124_mux_id);
+
+static struct platform_driver bd79124_mux_driver = {
+	.driver = {
+		.name = "bd79124-pinmux",
+		/*
+		 * Probing explicitly requires a few millisecond of sleep.
+		 * Enabling the VDD regulator may include ramp up rates.
+		 */
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+	.probe = bd79124_probe,
+	.id_table = bd79124_mux_id,
+};
+module_platform_driver(bd79124_mux_driver);
+
+MODULE_AUTHOR("Matti Vaittinen <mazziesaccount@gmail.com>");
+MODULE_DESCRIPTION("Pinmux/GPO Driver for ROHM BD79124");
+MODULE_LICENSE("GPL");