Re: [PATCH v13 3/7] mfd: p3h2x4x: Add driver for NXP P3H2x4x i3c hub and on-die regulator

[Lee Jones <lee@kernel.org>]

On Wed, 01 Jul 2026, Lakshay Piplani wrote:

> 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.
> 
> 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 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       | 126 ++++++++++++++++++++++++++++++++++++
>  include/linux/i3c/device.h  |   1 +
>  include/linux/mfd/p3h2840.h |  28 ++++++++
>  6 files changed, 171 insertions(+)
>  create mode 100644 drivers/mfd/p3h2840.c
>  create mode 100644 include/linux/mfd/p3h2840.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ba65ae5a008b..3420701a75c5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -19311,6 +19311,8 @@ 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 7192c9d1d268..405b50c3c77b 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 e75e8045c28a..a284b22c7b13 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..89a97f0449c4
> --- /dev/null
> +++ b/drivers/mfd/p3h2840.c
> @@ -0,0 +1,126 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2025-2026 NXP

Nit: '\n' here.

> + * P3H2X4X i3c hub and regulator device.

Those describe the children, not this device.

No Author: ?

> + */
> +
> +#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"),

Too many tabs.

> +};
> +
> +static const struct regmap_config p3h2x4x_regmap_config = {
> +	.reg_bits = P3H2X4X_REG_BITS,
> +	.val_bits = P3H2X4X_VAL_BITS,
> +	.max_register = 0xFF,
> +};
> +
> +static int p3h2x4x_device_probe_i3c(struct i3c_device *i3cdev)

How many of these are comming down the pipe?

Might be worth expanding drivers/mfd/simple-mfd-i2c.c instead?

> +{
> +	struct device *dev = i3cdev_to_dev(i3cdev);
> +	struct i3c_device_info info;

devinfo is more consistent.

> +	struct p3h2x4x_dev *ddata;

Drop the _dev part.

> +	int ret;
> +
> +	i3c_device_get_info(i3cdev, &info);
> +
> +	if (I3C_PID_MANUF_ID(info.pid) != I3C_MANUF_ID_NXP)
> +		return -ENODEV;
> +
> +	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
> +	if (!ddata)
> +		return -ENOMEM;
> +
> +	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

C++ comments?

> +	ddata->i3cdev = i3cdev;
> +
> +	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_dev *ddata;
> +	int ret;
> +
> +	ddata = devm_kzalloc(&client->dev, sizeof(*ddata), GFP_KERNEL);
> +	if (!ddata)
> +		return -ENOMEM;
> +
> +	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 = 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[] = {
> +	{ "nxp-i3c-hub" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, p3h2x4x_i2c_id_table);
> +
> +static const struct of_device_id p3h2x4x_i2c_of_match[] = {
> +	{ .compatible = "nxp,p3h2840", },
> +	{ /* 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,

Is there an accidental double space before '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 971d53349b6f..6188082599dd 100644
> --- a/include/linux/i3c/device.h
> +++ b/include/linux/i3c/device.h
> @@ -85,6 +85,7 @@ struct i3c_xfer {
>   */
>  enum i3c_dcr {
>  	I3C_DCR_GENERIC_DEVICE = 0,
> +	I3C_DCR_HUB = 194,

What is this value?

>  };
>  
>  #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..0f0d5b442bef
> --- /dev/null
> +++ b/include/linux/mfd/p3h2840.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright 2025-2026 NXP
> + * This header file contains register definitions and bit masks for the P3H2X4X.

This comment is superfluous .

> + */
> +
> +#ifndef _LINUX_MFD_P3H2840_H
> +#define _LINUX_MFD_P3H2840_H
> +
> +#include <linux/types.h>
> +
> +/* 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
> +
> +/* Reg config for Regmap */
> +#define P3H2X4X_REG_BITS					8
> +#define P3H2X4X_VAL_BITS					8

It's not common to define these values.

> +#define I3C_MANUF_ID_NXP					0x011b
> +
> +struct p3h2x4x_dev {
> +	struct i3c_device *i3cdev;
> +	struct regmap *regmap;
> +};
> +#endif /* _LINUX_MFD_P3H2840_H */
> -- 
> 2.25.1
> 

-- 
Lee Jones