Re: [PATCH v12 1/1] mux: Add driver for Renesas RZ/V2H USB VBENCTL VBUS_SEL mux

Hi!

Sorry for the late reply.

On 2026-07-15 12:12, Tommaso Merciai wrote:
> As per the RZ/V2H(P) HW manual, VBUSEN can be controlled by the VBUS_SEL
> bit of the VBENCTL Control Register. This register is mapped in the
> reset framework. The reset driver expose this register as mux-controller
> and instantiates this driver. The consumer will use the mux API to
> control the VBUS_SEL bit.
> 
> Reviewed-by: Philipp Zabel <[email protected]>
> Signed-off-by: Tommaso Merciai <[email protected]>
> ---
> v11->v12
>  - No changes, just rebased on top of next-20260714
> 
> v10->v11:
>  - No changes.
> 
> v9->v10:
>  - No changes.
> 
> v8->v9:
>  - Fixed driver comment year (2025 -> 2026)
>  - Switch from devm_regmap_init_mmio() to dev_get_regmap().
>  - Drop unnecessasry include bitops.h, of.h, property.h and
>    drivers/reset/reset-rzv2h-usb2phy.h headers, driver is now based on regmap.
>  - Collected PZabel tag.
> 
> v7->v8:
>  - No changes.
> 
> v6->v7:
>  - No changes.
> 
> v5->v6:
>  - No changes.
> 
> v4->v5:
>  - Changed file name to rzv2h-usb-vbenctl.c and Fixed
>    Makefile, Kconfig, function names accordingly.
>  - Changed driver .name to "vbenctl" and fix auxiliary_device_id name.
>  - Updated commit msg.
> 
> v3->v4:
>  - Removed mux_chip->dev.of_node not needed.
> 
> v2->v3:
>  - Added mux_chip->dev.of_node = dev->of_node->child as the mux-controller
>    is an internal node.
>  - Fixed auxiliary_device_id name.
>  - Get rdev using from platform_data.
>  - Drop struct auxiliary_device adev from reset_rzv2h_usb2phy_adev
>    as it is needed.
>  - Drop to_reset_rzv2h_usb2phy_adev() as it is not needed.
> 
> v1->v2:
>  - New patch
> 
>  drivers/mux/Kconfig             | 11 +++++
>  drivers/mux/Makefile            |  2 +
>  drivers/mux/rzv2h-usb-vbenctl.c | 85 +++++++++++++++++++++++++++++++++
>  3 files changed, 98 insertions(+)
>  create mode 100644 drivers/mux/rzv2h-usb-vbenctl.c
> 
> diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
> index 6d17dfa25dad..7f334540c189 100644
> --- a/drivers/mux/Kconfig
> +++ b/drivers/mux/Kconfig
> @@ -70,6 +70,17 @@ config MUX_MMIO
>  	  To compile the driver as a module, choose M here: the module will
>  	  be called mux-mmio.
>  
> +config MUX_RZV2H_USB_VBENCTL

Do we really need such a long name? Can we skip at least some part
of it, e.g. "USB_"? I see little in this driver that relates to
USB. And then propagate the shorter name to the file name and
various identifiers of course. Please?

> +	tristate "Renesas RZ/V2H USB VBENCTL VBUS_SEL mux driver"
> +	depends on RESET_RZV2H_USB2PHY || COMPILE_TEST
> +	depends on OF

Why OF?

> +	select REGMAP
> +	select AUXILIARY_BUS
> +	default RESET_RZV2H_USB2PHY
> +	help
> +	  Support for USB VBENCTL VBUS_SEL mux implemented on Renesas
> +	  RZ/V2H SoCs.

All the other drivers have a boilerplate "module paragraph" here:

	  To compile the driver as a module, choose M here: the module will
	  be called mux-<gazonk>.

I see no reason to exclude it here.

> +
>  endmenu
>  
>  endif # MULTIPLEXER
> diff --git a/drivers/mux/Makefile b/drivers/mux/Makefile
> index 6e9fa47daf56..3bd9b3846835 100644
> --- a/drivers/mux/Makefile
> +++ b/drivers/mux/Makefile
> @@ -8,9 +8,11 @@ mux-adg792a-objs		:= adg792a.o
>  mux-adgs1408-objs		:= adgs1408.o
>  mux-gpio-objs			:= gpio.o
>  mux-mmio-objs			:= mmio.o
> +mux-rzv2h-usb-vbenctl-objs	:= rzv2h-usb-vbenctl.o
>  
>  obj-$(CONFIG_MULTIPLEXER)	+= mux-core.o
>  obj-$(CONFIG_MUX_ADG792A)	+= mux-adg792a.o
>  obj-$(CONFIG_MUX_ADGS1408)	+= mux-adgs1408.o
>  obj-$(CONFIG_MUX_GPIO)		+= mux-gpio.o
>  obj-$(CONFIG_MUX_MMIO)		+= mux-mmio.o
> +obj-$(CONFIG_MUX_RZV2H_USB_VBENCTL)	+= mux-rzv2h-usb-vbenctl.o
> diff --git a/drivers/mux/rzv2h-usb-vbenctl.c b/drivers/mux/rzv2h-usb-vbenctl.c
> new file mode 100644
> index 000000000000..79197fddbf74
> --- /dev/null
> +++ b/drivers/mux/rzv2h-usb-vbenctl.c
> @@ -0,0 +1,85 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Renesas RZ/V2H(P) USB VBENCTL VBUS_SEL mux driver
> + *
> + * Copyright (C) 2026 Renesas Electronics Corp.
> + */
> +
> +#include <linux/auxiliary_bus.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/mux/driver.h>
> +#include <linux/regmap.h>
> +
> +#define RZV2H_VBENCTL		0xf0c
> +
> +struct mux_rzv2h_usb_vbenctl_priv {
> +	struct regmap_field *field;
> +};
> +
> +static int mux_rzv2h_usb_vbenctl_set(struct mux_control *mux, int state)
> +{
> +	struct mux_rzv2h_usb_vbenctl_priv *priv = mux_chip_priv(mux->chip);
> +
> +	return regmap_field_write(priv->field, state);
> +}
> +
> +static const struct mux_control_ops mux_rzv2h_usb_vbenctl_ops = {
> +	.set = mux_rzv2h_usb_vbenctl_set,
> +};
> +
> +static int mux_rzv2h_usb_vbenctl_probe(struct auxiliary_device *adev,
> +				       const struct auxiliary_device_id *id)
> +{
> +	struct mux_rzv2h_usb_vbenctl_priv *priv;
> +	struct device *dev = &adev->dev;
> +	struct mux_chip *mux_chip;
> +	struct regmap *regmap;
> +	struct reg_field reg_field = {
> +		.reg = RZV2H_VBENCTL,
> +		.lsb = 0,
> +		.msb = 0,
> +	};

Perhaps

	struct reg_field reg_field = REG_FIELD(RZV2H_VBENCTL, 0, 0);

> +	int ret;
> +
> +	regmap = dev_get_regmap(adev->dev.parent, NULL);

Perhaps

	regmap = dev_get_regmap(dev->parent, NULL);

> +	if (!regmap)
> +		return -ENODEV;
> +
> +	mux_chip = devm_mux_chip_alloc(dev, 1, sizeof(*priv));
> +	if (IS_ERR(mux_chip))
> +		return PTR_ERR(mux_chip);
> +
> +	priv = mux_chip_priv(mux_chip);
> +
> +	priv->field = devm_regmap_field_alloc(dev, regmap, reg_field);
> +	if (IS_ERR(priv->field))
> +		return PTR_ERR(priv->field);
> +
> +	mux_chip->ops = &mux_rzv2h_usb_vbenctl_ops;
> +	mux_chip->mux[0].states = 2;
> +	mux_chip->mux[0].idle_state = MUX_IDLE_AS_IS;
> +
> +	ret = devm_mux_chip_register(dev, mux_chip);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "Failed to register mux chip\n");
> +
> +	return 0;
> +}
> +
> +static const struct auxiliary_device_id mux_rzv2h_usb_vbenctl_ids[] = {
> +	{ .name = "rzv2h_usb2phy_reset.vbenctl" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(auxiliary, mux_rzv2h_usb_vbenctl_ids);
> +
> +static struct auxiliary_driver mux_rzv2h_usb_vbenctl_driver = {
> +	.name		= "vbenctl",
> +	.probe		= mux_rzv2h_usb_vbenctl_probe,
> +	.id_table	= mux_rzv2h_usb_vbenctl_ids,
> +};
> +module_auxiliary_driver(mux_rzv2h_usb_vbenctl_driver);
> +

I'm not previously familiar with the auxiliary bus. When I read about
it I find this:

	"A key requirement for utilizing the auxiliary bus is that
	there is no dependency on a physical bus, device, register
	accesses or regmap support."

That seems to contradict this driver with its dependency on regmap,
thus violating the above key requirement?

Cheers,
Peter

> +MODULE_DESCRIPTION("RZ/V2H USB VBENCTL VBUS_SEL mux driver");
> +MODULE_AUTHOR("Tommaso Merciai <[email protected]>");
> +MODULE_LICENSE("GPL");