[PATCH v18 4/8] mfd: p3h2x4x: Add driver for NXP P3H2x4x i3c hub and on-die regulator

[Lakshay Piplani <lakshay.piplani@nxp.com>]

From: Aman Kumar Pandey <aman.kumarpandey@nxp.com>

Add core MFD support for the NXP P3H2x4x (P3H2440/P3H2441/P3H2840/P3H2841)
family of multiport I3C hub devices. These devices connect to a host via
I3C/I2C/SMBus and expose multiple downstream target ports.

All variants share the same register interface. The driver reads the
target-port count from DEV_CAPAB and applies the DT configuration, so no
per-compatible driver data is required.

Signed-off-by: Aman Kumar Pandey <aman.kumarpandey@nxp.com>
Signed-off-by: Vikash Bansal <vikash.bansal@nxp.com>
Signed-off-by: Lakshay Piplani <lakshay.piplani@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>

---
Changes in v18:
 - Rebased onto v7.3-rc1; no intended driver behaviour changes

Changes in v17:
 - No change

Changes in v16:
 - Use a named initializer for struct i2c_device_id
  ({ .name = "nxp-i3c-hub" })
 - Keep the shared header in include/linux/mfd/ (struct p3h2x4x is shared by
   the mfd parent and its regulator/i3c-hub children). The i3c_hub_priv
   back-pointer is retained for IBI routing, with documented publish/clear
   ordering

Changes in v15:
 - Read the device capability register to determine whether the device has
   four or eight target ports
 - Store the detected target-port count in the shared MFD data
 - Add OF match entries for all P3H2440, P3H2441, P3H2840 and P3H2841
   variants
 - Add a shared hub-context pointer for use by the IBI handler without
   overwriting the MFD parent's driver data

Changes in v14:
 - Clean up MFD driver comments, formatting, variable names and author
   information
 - Define and document the I3C hub DCR value in hexadecimal form
 - Use direct regmap bit-width values instead of local macros
 - Add a shared protected_reg_lock for protected register accesses across
   P3H2X4X child drivers

Changes in v13:
 - Use i3c_device helpers (i3cdev_to_dev()) instead of direct struct access
   to maintain API abstraction
 - Avoid including internal I3C headers and use public device headers instead
 - Ensure proper device matching by relying on manufacturer ID checks in probe

Changes in v12:
 - No change, added Reviewed-By tag

Changes in v11:
 - Use MFD_CELL_NAME() for child device registration
 - Rename local variables for consistency
 - Rename driver names to follow subsystem conventions:
   - Use '-' instead of '_' in driver names
   - Drop the "_drv" suffix from driver names

Changes in v10:
 - Drop redundant is_p3h2x4x_in_i3c flag

Changes in v9:
 - Renamed macros to follow consistent uppercase naming conventions
 - Made REGMAP selects in the P3H2X4X MFD Kconfig conditional,
   to avoid I3C/I2C dependency issues

Changes in v8:
 - No change

Changes in v7:
 - Use new config I3C_OR_I2C

Changes in v6:
 - No change

Changes in v5:
 - Corrected the ordering in the Makefile and Kconfig for MFD_P3H2X4X
 - Updated dev_err_probe() for regmap_init failure.
 - Updated module description

Changes in v4:
 - Split the driver into three separate patches(mfd, regulator and I3C hub)
 - Added support for NXP P3H2x4x MFD functionality
---
---
 MAINTAINERS                 |   2 +
 drivers/mfd/Kconfig         |  13 +++
 drivers/mfd/Makefile        |   1 +
 drivers/mfd/p3h2840.c       | 167 ++++++++++++++++++++++++++++++++++++
 include/linux/i3c/device.h  |   2 +
 include/linux/mfd/p3h2840.h |  41 +++++++++
 6 files changed, 226 insertions(+)
 create mode 100644 drivers/mfd/p3h2840.c
 create mode 100644 include/linux/mfd/p3h2840.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 203e6e8ae2f9..d482a23c0bf7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19771,6 +19771,8 @@ L:	linux-kernel@vger.kernel.org
 L:	linux-i3c@lists.infradead.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/i3c/nxp,p3h2840.yaml
+F:	drivers/mfd/p3h2840.c
+F:	include/linux/mfd/p3h2840.h
 
 NXP PF5300/PF5301/PF5302 PMIC REGULATOR DEVICE DRIVER
 M:	Woodrow Douglass <wdouglass@carnegierobotics.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index e4fd4572472f..ee809b0c1b8f 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -617,6 +617,19 @@ config MFD_MX25_TSADC
 	  i.MX25 processors. They consist of a conversion queue for general
 	  purpose ADC and a queue for Touchscreens.
 
+config MFD_P3H2X4X
+	tristate "NXP P3H2X4X I3C Hub Device"
+	depends on I3C_OR_I2C
+	select MFD_CORE
+	select REGMAP_I3C if I3C
+	select REGMAP_I2C if I2C
+	help
+	  Enable Support for NXP P3H244x/P3H284x I3C HUB device using I3C/I2C
+	  communication interface.
+
+	  This driver provides support for I3C hub and regulator, each subdriver
+	  can be enabled independently depending on the required functionality.
+
 config MFD_PF1550
 	tristate "NXP PF1550 PMIC Support"
 	depends on I2C=y && OF
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 72d3944b0ad8..ec4e093f3540 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -122,6 +122,7 @@ obj-$(CONFIG_MFD_MC13XXX)	+= mc13xxx-core.o
 obj-$(CONFIG_MFD_MC13XXX_SPI)	+= mc13xxx-spi.o
 obj-$(CONFIG_MFD_MC13XXX_I2C)	+= mc13xxx-i2c.o
 
+obj-$(CONFIG_MFD_P3H2X4X)	+= p3h2840.o
 obj-$(CONFIG_MFD_PF1550)	+= pf1550.o
 
 obj-$(CONFIG_MFD_NCT6694)	+= nct6694.o
diff --git a/drivers/mfd/p3h2840.c b/drivers/mfd/p3h2840.c
new file mode 100644
index 000000000000..d81cb2a5b7da
--- /dev/null
+++ b/drivers/mfd/p3h2840.c
@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2025-2026 NXP
+ *
+ * Authors:
+ *	Aman Kumar Pandey <aman.kumarpandey@nxp.com>
+ *	Vikash Bansal <vikash.bansal@nxp.com>
+ *	Lakshay Piplani <lakshay.piplani@nxp.com>
+ *
+ * NXP P3H2x4x multi-port I3C hub.
+ */
+#include <linux/i2c.h>
+#include <linux/i3c/device.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/p3h2840.h>
+#include <linux/regmap.h>
+
+static const struct mfd_cell p3h2x4x_devs[] = {
+	MFD_CELL_NAME("p3h2x4x-regulator"),
+	MFD_CELL_NAME("p3h2x4x-i3c-hub"),
+};
+
+static const struct regmap_config p3h2x4x_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0xFF,
+};
+
+/* Read port count from the device capability register (4- or 8-port variant). */
+static int p3h2x4x_read_num_target_ports(struct device *dev,
+					 struct p3h2x4x *ddata)
+{
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(ddata->regmap, P3H2X4X_DEV_CAPAB, &val);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to read device capability\n");
+
+	ddata->num_target_ports = (val & P3H2X4X_TARGET_PORT_COUNT) ?
+		P3H2X4X_TARGET_PORTS_8 : P3H2X4X_TARGET_PORTS_4;
+
+	return 0;
+}
+
+static int p3h2x4x_device_probe_i3c(struct i3c_device *i3cdev)
+{
+	struct device *dev = i3cdev_to_dev(i3cdev);
+	struct i3c_device_info devinfo;
+	struct p3h2x4x *ddata;
+	int ret;
+
+	i3c_device_get_info(i3cdev, &devinfo);
+	if (I3C_PID_MANUF_ID(devinfo.pid) != I3C_MANUF_ID_NXP)
+		return -ENODEV;
+
+	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	ret = devm_mutex_init(dev, &ddata->protected_reg_lock);
+	if (ret)
+		return ret;
+
+	i3cdev_set_drvdata(i3cdev, ddata);
+
+	ddata->regmap = devm_regmap_init_i3c(i3cdev, &p3h2x4x_regmap_config);
+	if (IS_ERR(ddata->regmap))
+		return dev_err_probe(dev, PTR_ERR(ddata->regmap),
+				     "Failed to register HUB regmap\n");
+
+	/* The hub child driver retrieves information from i3cdev. */
+	ddata->i3cdev = i3cdev;
+
+	ret = p3h2x4x_read_num_target_ports(dev, ddata);
+	if (ret)
+		return ret;
+
+	ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
+				   p3h2x4x_devs, ARRAY_SIZE(p3h2x4x_devs),
+				   NULL, 0, NULL);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to add sub devices\n");
+
+	return 0;
+}
+
+static int p3h2x4x_device_probe_i2c(struct i2c_client *client)
+{
+	struct p3h2x4x *ddata;
+	int ret;
+
+	ddata = devm_kzalloc(&client->dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	ret = devm_mutex_init(&client->dev, &ddata->protected_reg_lock);
+	if (ret)
+		return ret;
+
+	i2c_set_clientdata(client, ddata);
+
+	ddata->regmap = devm_regmap_init_i2c(client, &p3h2x4x_regmap_config);
+	if (IS_ERR(ddata->regmap))
+		return dev_err_probe(&client->dev, PTR_ERR(ddata->regmap),
+				     "Failed to register HUB regmap\n");
+
+	ddata->i3cdev = NULL;
+
+	ret = p3h2x4x_read_num_target_ports(&client->dev, ddata);
+	if (ret)
+		return ret;
+
+	ret = devm_mfd_add_devices(&client->dev, PLATFORM_DEVID_AUTO,
+				   p3h2x4x_devs, ARRAY_SIZE(p3h2x4x_devs),
+				   NULL, 0, NULL);
+	if (ret)
+		return dev_err_probe(&client->dev, ret, "Failed to add sub devices\n");
+
+	return 0;
+}
+
+static const struct i3c_device_id p3h2x4x_i3c_ids[] = {
+	I3C_CLASS(I3C_DCR_HUB, NULL),
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(i3c, p3h2x4x_i3c_ids);
+
+static const struct i2c_device_id p3h2x4x_i2c_id_table[] = {
+	{ .name = "nxp-i3c-hub" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, p3h2x4x_i2c_id_table);
+
+static const struct of_device_id p3h2x4x_i2c_of_match[] = {
+	{ .compatible = "nxp,p3h2440", },
+	{ .compatible = "nxp,p3h2441", },
+	{ .compatible = "nxp,p3h2840", },
+	{ .compatible = "nxp,p3h2841", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, p3h2x4x_i2c_of_match);
+
+static struct i3c_driver p3h2x4x_i3c = {
+	.driver = {
+		.name = "p3h2x4x-i3c",
+	},
+	.probe = p3h2x4x_device_probe_i3c,
+	.id_table = p3h2x4x_i3c_ids,
+};
+
+static struct i2c_driver p3h2x4x_i2c = {
+	.driver = {
+		.name = "p3h2x4x-i2c",
+		.of_match_table = p3h2x4x_i2c_of_match,
+	},
+	.probe = p3h2x4x_device_probe_i2c,
+	.id_table = p3h2x4x_i2c_id_table,
+};
+module_i3c_i2c_driver(p3h2x4x_i3c, &p3h2x4x_i2c);
+
+MODULE_AUTHOR("Aman Kumar Pandey <aman.kumarpandey@nxp.com>");
+MODULE_AUTHOR("Vikash Bansal <vikash.bansal@nxp.com>");
+MODULE_AUTHOR("Lakshay Piplani <lakshay.piplani@nxp.com>");
+MODULE_DESCRIPTION("NXP P3H2X4X I3C HUB multi function driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/i3c/device.h b/include/linux/i3c/device.h
index 0f065b883ee0..d008688c96f6 100644
--- a/include/linux/i3c/device.h
+++ b/include/linux/i3c/device.h
@@ -82,9 +82,11 @@ struct i3c_xfer {
 /**
  * enum i3c_dcr - I3C DCR values
  * @I3C_DCR_GENERIC_DEVICE: generic I3C device
+ * @I3C_DCR_HUB: I3C hub device
  */
 enum i3c_dcr {
 	I3C_DCR_GENERIC_DEVICE = 0,
+	I3C_DCR_HUB = 0xC2,
 };
 
 #define I3C_PID_MANUF_ID(pid)		(((pid) & GENMASK_ULL(47, 33)) >> 33)
diff --git a/include/linux/mfd/p3h2840.h b/include/linux/mfd/p3h2840.h
new file mode 100644
index 000000000000..eb4792de5440
--- /dev/null
+++ b/include/linux/mfd/p3h2840.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2025-2026 NXP
+ */
+
+#ifndef _LINUX_MFD_P3H2840_H
+#define _LINUX_MFD_P3H2840_H
+
+#include <linux/bits.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+
+/* Device Information Registers */
+#define P3H2X4X_DEV_CAPAB					0x0a
+#define P3H2X4X_TARGET_PORT_COUNT				BIT(3)
+
+/* Downstream target port counts per variant. */
+#define P3H2X4X_TARGET_PORTS_4					4
+#define P3H2X4X_TARGET_PORTS_8					8
+
+/* Device Configuration Registers */
+#define P3H2X4X_DEV_REG_PROTECTION_CODE				0x10
+#define P3H2X4X_REGISTERS_LOCK_CODE				0x00
+#define P3H2X4X_REGISTERS_UNLOCK_CODE				0x69
+#define P3H2X4X_CP1_REGISTERS_UNLOCK_CODE			0x6a
+
+#define I3C_MANUF_ID_NXP					0x011b
+
+struct p3h2x4x_i3c_hub_dev;
+
+struct p3h2x4x {
+	struct i3c_device *i3cdev;
+	struct regmap *regmap;
+	/* Number of downstream target ports (4 or 8). */
+	u8 num_target_ports;
+	/* Serializes protected register unlock/lock sequences across MFD children. */
+	struct mutex protected_reg_lock;
+	/* Hub context for the IBI handler to reach hub state via the parent i3cdev. */
+	struct p3h2x4x_i3c_hub_dev *i3c_hub_priv;
+};
+#endif /* _LINUX_MFD_P3H2840_H */
-- 
2.25.1