linux-kernel - Re: [PATCH v4 3/5] mfd: p3h2x4x: Add driver for NXP P3H2x4x i3c hub and on-die regulator

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Message-ID: <20260114-refreshing-groovy-buzzard-af2eeb@quoll>
Date: Wed, 14 Jan 2026 09:28:53 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Aman Kumar Pandey <aman.kumarpandey@....com>
Cc: linux-kernel@...r.kernel.org, linux-i3c@...ts.infradead.org, 
	alexandre.belloni@...tlin.com, krzk+dt@...nel.org, robh@...nel.org, conor+dt@...nel.org, 
	devicetree@...r.kernel.org, broonie@...nel.org, lee@...nel.org, Frank.Li@....com, 
	lgirdwood@...il.com, vikash.bansal@....com, priyanka.jain@....com, 
	shashank.rebbapragada@....com
Subject: Re: [PATCH v4 3/5] mfd: p3h2x4x: Add driver for NXP P3H2x4x i3c hub
 and on-die regulator

On Tue, Jan 13, 2026 at 01:45:27PM +0200, Aman Kumar Pandey wrote:
> 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.
> 
> This patch introduces the MFD driver that registers sub-devices for the
> I3C hub and on-die regulators.
> 
> Signed-off-by: Aman Kumar Pandey <aman.kumarpandey@....com>
> Signed-off-by: Vikash Bansal <vikash.bansal@....com>
> 
> ---
> Changes in v4:
>  - Split the driver into three separate patches(mfd, regulator and I3C hub)
>  - Added support for NXP P3H2x4x MFD functionality
> ---
> ---
>  MAINTAINERS                 |   4 ++
>  drivers/mfd/Kconfig         |  12 ++++
>  drivers/mfd/Makefile        |   2 +
>  drivers/mfd/p3h2840.c       | 128 ++++++++++++++++++++++++++++++++++++
>  include/linux/mfd/p3h2840.h |  22 +++++++
>  5 files changed, 168 insertions(+)
>  create mode 100644 drivers/mfd/p3h2840.c
>  create mode 100644 include/linux/mfd/p3h2840.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 03a66efbcc4c..aa7043499223 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18931,6 +18931,10 @@ L:	linux-kernel@...r.kernel.org
>  L:	linux-i3c-owner@...ts.infradead.org
>  S:	Maintained
>  F:	Documentation/devicetree/bindings/mfd/nxp,p3h2840-i3c-hub.yaml
> +F:	drivers/mfd/Kconfig
> +F:	drivers/mfd/Makefile

What?

> +F:	drivers/mfd/p3h2840.c
> +F:	include/linux/mfd/p3h2840.h
>  
>  NXP SGTL5000 DRIVER
>  M:	Fabio Estevam <festevam@...il.com>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index aace5766b38a..6c41beb0db88 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -2540,6 +2540,18 @@ config MFD_RSMU_SPI
>  	  Additional drivers must be enabled in order to use the functionality
>  	  of the device.
>  
> +config MFD_P3H2X4X
> +       tristate "NXP P3H2X4X I3C Hub Device"
> +       depends on I3C
> +       select MFD_CORE
> +       select REGMAP_I3C
> +       help
> +         Enable Support for NXP P3H244x/P3H284x I3C HUB device using I3C/I2c
> +         communication interface.
> +
> +         This driver provides support for I3C Hub and regulator, additional
> +         drivers must be enabled in order to use the functionality of the device.
> +
>  config MFD_UPBOARD_FPGA
>  	tristate "Support for the AAeon UP board FPGA"
>  	depends on (X86 && ACPI)
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index e75e8045c28a..223142cdd803 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -301,6 +301,8 @@ obj-$(CONFIG_MFD_QNAP_MCU)	+= qnap-mcu.o
>  obj-$(CONFIG_MFD_RSMU_I2C)	+= rsmu_i2c.o rsmu_core.o
>  obj-$(CONFIG_MFD_RSMU_SPI)	+= rsmu_spi.o rsmu_core.o
>  
> +obj-$(CONFIG_MFD_P3H2X4X) 	+= p3h2840.o

Do not add at the end of Makefile or Kconfig. P < R if you wanted to
order it around here, but probably should be placed much earlier.

> +
>  obj-$(CONFIG_MFD_UPBOARD_FPGA)	+= upboard-fpga.o
>  
>  obj-$(CONFIG_MFD_LOONGSON_SE)	+= loongson-se.o
> diff --git a/drivers/mfd/p3h2840.c b/drivers/mfd/p3h2840.c
> new file mode 100644
> index 000000000000..f6a99291c305
> --- /dev/null
> +++ b/drivers/mfd/p3h2840.c
> @@ -0,0 +1,128 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2025 NXP
> + * P3H2x4x i3c hub and regulator device.
> + */
> +
> +#include <linux/i3c/master.h>
> +#include <linux/i2c.h>
> +#include <linux/mfd/core.h>
> +#include <linux/regmap.h>
> +#include <linux/mfd/p3h2840.h>
> +
> +static const struct mfd_cell p3h2x4x_devs[] = {
> +	{
> +		.name = "p3h2x4x-regulator",
> +	},
> +	{
> +		.name = "p3h2x4x-i3c-hub",
> +	},
> +};
> +
> +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)
> +{
> +	struct p3h2x4x_dev *p3h2x4x;
> +	int ret;
> +
> +	p3h2x4x = devm_kzalloc(&i3cdev->dev, sizeof(*p3h2x4x), GFP_KERNEL);
> +	if (!p3h2x4x)
> +		return -ENOMEM;
> +
> +	i3cdev_set_drvdata(i3cdev, p3h2x4x);
> +
> +	p3h2x4x->regmap = devm_regmap_init_i3c(i3cdev, &p3h2x4x_regmap_config);
> +	if (IS_ERR(p3h2x4x->regmap)) {
> +		return dev_err_probe(&i3cdev->dev, PTR_ERR(p3h2x4x->regmap),

Look here...

> +				     "Failed to register I3C HUB regmap\n");
> +	}
> +
> +	p3h2x4x->is_p3h2x4x_in_i3c = true;
> +	p3h2x4x->i3cdev = i3cdev;
> +
> +	ret = devm_mfd_add_devices(&i3cdev->dev, PLATFORM_DEVID_NONE,
> +				   p3h2x4x_devs, ARRAY_SIZE(p3h2x4x_devs),
> +				   NULL, 0, NULL);
> +	if (ret)
> +		return dev_err_probe(&i3cdev->dev, ret, "Failed to add sub devices\n");
> +
> +	return 0;
> +}
> +
> +static int p3h2x4x_device_probe_i2c(struct i2c_client *client)
> +{
> +	struct p3h2x4x_dev *p3h2x4x;
> +	int ret;
> +
> +	p3h2x4x = devm_kzalloc(&client->dev, sizeof(*p3h2x4x), GFP_KERNEL);
> +	if (!p3h2x4x)
> +		return -ENOMEM;
> +
> +	i2c_set_clientdata(client, p3h2x4x);
> +
> +	p3h2x4x->regmap = devm_regmap_init_i2c(client, &p3h2x4x_regmap_config);
> +	if (IS_ERR(p3h2x4x->regmap)) {
> +		ret = PTR_ERR(p3h2x4x->regmap);

And here!

Drop. This is completely redundant. How is it that in one place you use
one syntax and in other place completely different syntax?

> +		return dev_err_probe(&client->dev, ret, "Failed to register I3C HUB regmap\n");
> +	}
> +
> +	p3h2x4x->is_p3h2x4x_in_i3c = false;
> +	p3h2x4x->i2c_client = client;
> +
> +	ret = devm_mfd_add_devices(&client->dev, PLATFORM_DEVID_NONE,
> +				   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;

Best regards,
Krzysztof