Re: [PATCH v7 2/2] mfd: ac200: Add X-Powers AC200 support

[Lee Jones <lee@kernel.org>]

On Wed, 02 Sep 2026, James Hilliard wrote:

> On Wed, Sep 2, 2026 at 8:31 AM Lee Jones <lee@kernel.org> wrote:
> >
> > On Tue, 11 Aug 2026, James Hilliard wrote:
> >
> > > The X-Powers AC200 is a mixed-signal companion IC with a paged register
> > > map accessed over I2C.
> > >
> > > Enable the shared input clock and prevent its rate from changing. Match
> > > the vendor driver's 40 ms wait before the first register access,
> > > initialize the paged regmap, report the chip and package revision, and
> > > apply common reset.
> > >
> > > The Ethernet PHY link endpoint is independently enumerated on its MDIO
> > > bus rather than created as an MFD platform child. Keep the regmap attached
> > > to the AC200 I2C device so a separately enumerated function can resolve
> > > that device, establish its required lifetime relationship and retrieve
> > > the regmap from the provider.
> > >
> > > Cache only the common page selector. Individual functions can reset
> > > independently and invalidate their other registers without regmap's
> > > knowledge, so leave all functional registers volatile.
> > >
> > > Reset the chip during managed teardown and system shutdown.
> > >
> > > Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
> > > ---
> > >  drivers/mfd/Kconfig  |  11 ++++
> > >  drivers/mfd/Makefile |   1 +
> > >  drivers/mfd/ac200.c  | 163 +++++++++++++++++++++++++++++++++++++++++++++++++++
> > >  3 files changed, 175 insertions(+)
> > >
> > > diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> > > index e4fd4572472f..cac3fff5aee9 100644
> > > --- a/drivers/mfd/Kconfig
> > > +++ b/drivers/mfd/Kconfig
> > > @@ -205,6 +205,17 @@ config MFD_AC100
> > >         This driver include only the core APIs. You have to select individual
> > >         components like codecs or RTC under the corresponding menus.
> > >
> > > +config MFD_AC200
> > > +     tristate "X-Powers AC200"
> > > +     depends on I2C
> > > +     depends on OF
> > > +     select REGMAP_I2C
> > > +     help
> > > +       Support for the X-Powers AC200 mixed-signal companion IC. The AC200
> > > +       contains audio, video, RTC and Fast Ethernet PHY functions and is
> > > +       co-packaged with some Allwinner H6 and H616 SoCs. This driver provides
> > > +       the shared register access used by the individual function drivers.
> > > +
> > >  config MFD_AXP20X
> > >       tristate
> > >       select MFD_CORE
> > > diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> > > index 72d3944b0ad8..f8101d2a9ce9 100644
> > > --- a/drivers/mfd/Makefile
> > > +++ b/drivers/mfd/Makefile
> > > @@ -150,6 +150,7 @@ obj-$(CONFIG_MFD_DA9052_SPI)      += da9052-spi.o
> > >  obj-$(CONFIG_MFD_DA9052_I2C) += da9052-i2c.o
> > >
> > >  obj-$(CONFIG_MFD_AC100)              += ac100.o
> > > +obj-$(CONFIG_MFD_AC200)              += ac200.o
> > >  obj-$(CONFIG_MFD_AXP20X)     += axp20x.o
> > >  obj-$(CONFIG_MFD_AXP20X_I2C) += axp20x-i2c.o
> > >  obj-$(CONFIG_MFD_AXP20X_RSB) += axp20x-rsb.o
> > > diff --git a/drivers/mfd/ac200.c b/drivers/mfd/ac200.c
> > > new file mode 100644
> > > index 000000000000..0964e637afef
> > > --- /dev/null
> > > +++ b/drivers/mfd/ac200.c
> > > @@ -0,0 +1,163 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * MFD core driver for the X-Powers AC200
> > > + *
> > > + * Copyright (C) 2019 Jernej Skrabec <jernej.skrabec@gmail.com>
> > > + * Copyright (C) 2026 James Hilliard <james.hilliard1@gmail.com>
> > > + *
> > > + * Based on the AC100 driver:
> > > + * Copyright (C) 2016 Chen-Yu Tsai
> >
> > Drop this.  Every driver tends to be based on something else.
> 
> Dropped in v8.
> 
> >
> > > + */
> > > +
> > > +#include <linux/bitfield.h>
> > > +#include <linux/clk.h>
> > > +#include <linux/delay.h>
> > > +#include <linux/i2c.h>
> > > +#include <linux/module.h>
> > > +#include <linux/regmap.h>
> >
> > Why aren't you using the MFD API?
> >
> > If you don't need it, then why is this in drivers/mfd?
> 
> The EPHY remains enumerated on its primary MDIO bus, so it is not an MFD
> child. For non-EPHY use cases, the AC200 audio, video and RTC functions
> are intended to be added as MFD children.
> 
> There are no such child drivers in this series, so I have not added
> unused MFD cells. Those can be introduced with their corresponding
> bindings and drivers.

The rule is that you must provide at least 2 MFD children before this
constitute as an MFD.  Please provide them in the same series.

-- 
Lee Jones