linux-kernel - Re: [PATCH RESEND v6 2/4] mfd: Support ROHM BD9576MUF and BD9573MUF

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Date:   Fri, 27 Nov 2020 09:44:08 +0000
From:   "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
To:     "lee.jones@...aro.org" <lee.jones@...aro.org>
CC:     "linux@...ck-us.net" <linux@...ck-us.net>,
        "wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
        "mazziesaccount@...il.com" <mazziesaccount@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        linux-power <linux-power@...rohmeurope.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Subject: Re: [PATCH RESEND v6 2/4] mfd: Support ROHM BD9576MUF and BD9573MUF

Hello Lee,

On Fri, 2020-11-27 at 08:32 +0000, Lee Jones wrote:
> On Mon, 23 Nov 2020, Matti Vaittinen wrote:
> 
> > Add core support for ROHM BD9576MUF and BD9573MUF PMICs which are
> > mainly used to power the R-Car series processors.
> > 
> > Signed-off-by: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
> > ---
> >  drivers/mfd/Kconfig              |  11 ++++
> >  drivers/mfd/Makefile             |   1 +
> >  drivers/mfd/rohm-bd9576.c        | 108
> > +++++++++++++++++++++++++++++++
> >  include/linux/mfd/rohm-bd957x.h  |  59 +++++++++++++++++
> >  include/linux/mfd/rohm-generic.h |   2 +
> >  5 files changed, 181 insertions(+)
> >  create mode 100644 drivers/mfd/rohm-bd9576.c
> >  create mode 100644 include/linux/mfd/rohm-bd957x.h
> 
> Looks like a possible candidate for "simple-mfd-i2c".
> 
> Could you look into that please?
> 
I must admit I didn't know about "simple-mfd-i2c". Good thing to know
when working with simple devices :) Is this a new thing?
I am unsure I understand the idea fully. Should users put all the
different regamp configs in this file and just add the device IDs with
pointer to correct config? (BD9576 and BD9573 need volatile ranges).
Also, does this mean each sub-device should have own node and own
compatible in DT to get correctly load and probed? I guess this would
need a buy-in from Rob too then.

By the way - for uneducated eyes like mine this does not look like it
has much to do with MFD as a device - here MFD reminds me of a simple-
bus on top of I2C.

Anyways, the BD9576 and BD9573 both have a few interrupts for OVD/UVD
conditions and I am expecting that I will be asked to provide the
regulator notifiers for those. Reason why I omitted the IRQs for now is
that the HW is designed to keep the IRQ asserted for whole error
duration so some delayed ack mechanism would be needed. I would like to
keep the door open for adding IRQs to MFD core.

Best Regards
	Matti