linux-kernel - RE: [PATCH v2 04/10] regulator: bd9571mwv: Add BD9574MWF support

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Date:   Mon, 14 Dec 2020 04:57:28 +0000
From:   Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To:     "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "marek.vasut+renesas@...il.com" <marek.vasut+renesas@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>
CC:     linux-power <linux-power@...rohmeurope.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Khiem Nguyen <khiem.nguyen.xt@...esas.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 04/10] regulator: bd9571mwv: Add BD9574MWF support

Hello Matti-san,

> From: Vaittinen, Matti, Sent: Friday, December 11, 2020 9:34 PM
> 
> Hello again Shimada-san,
> 
> On Fri, 2020-12-11 at 20:27 +0900, Yoshihiro Shimoda wrote:
> > Add support for BD9574MWF which is silimar chip with BD9571MWV.
> > Note that BD9574MWF doesn't support AVS and VID.
> 
> I'd like to understand what is VID?

It seems reading some voltages from registers.
For example, BD9571 has "VD18_VID" register which
is prohibit to write. But, BD9574 doesn't have this
register. Also, the driver names "vid_ops",
so I described "VID" here. Perhaps, we should revise
the description to clear. (Please look "Updated description" in this email.)

> >
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> > ---
> >  drivers/regulator/bd9571mwv-regulator.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/regulator/bd9571mwv-regulator.c
> > b/drivers/regulator/bd9571mwv-regulator.c
> > index 02120b0..041339b 100644
> > --- a/drivers/regulator/bd9571mwv-regulator.c
> > +++ b/drivers/regulator/bd9571mwv-regulator.c
> > @@ -1,6 +1,6 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  /*
> > - * ROHM BD9571MWV-M regulator driver
> > + * ROHM BD9571MWV-M and BD9574MWF-M regulator driver
> >   *
> >   * Copyright (C) 2017 Marek Vasut <marek.vasut+renesas@...il.com>
> >   *
> > @@ -9,6 +9,7 @@
> >   * NOTE: VD09 is missing
> >   */
> >
> > +#include <linux/mfd/rohm-generic.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> >  #include <linux/platform_device.h>
> > @@ -277,6 +278,7 @@ static int bd9571mwv_regulator_probe(struct
> > platform_device *pdev)
> >  	struct regulator_dev *rdev;
> >  	unsigned int val;
> >  	int i;
> > +	enum rohm_chip_type chip = platform_get_device_id(pdev)-
> > >driver_data;
> >
> >  	bdreg = devm_kzalloc(&pdev->dev, sizeof(*bdreg), GFP_KERNEL);
> >  	if (!bdreg)
> > @@ -292,6 +294,9 @@ static int bd9571mwv_regulator_probe(struct
> > platform_device *pdev)
> >  	config.regmap = bdreg->regmap;
> >
> >  	for (i = 0; i < ARRAY_SIZE(regulators); i++) {
> > +		/* BD9574MWF supports DVFS only */
> > +		if (chip == ROHM_CHIP_TYPE_BD9574 && regulators[i].id
> > != DVFS)
> > +			continue;
> 
> Does this mean that reading VD09 voltage is not supported by driver?

Yes. Also, reading VD{18,25,33} voltage are not supported.

> (I
> assumed VD09 initial voltage can be set from eeprom(?) and read by
> driver - I may be wrong though). Perhaps it is worth mentioning in the
> commit message as a driver restriction?

Yes, these voltage can be set from eeprom and read by driver.
So, I updated the description like below.

-- Updated description --
Add support for BD9574MWF which is similar chip with BD9571MWV.
Note that since BD9574MWF doesn't have avs_ops and vid_ops
related registers, this driver avoids to use these registers
if BD9574MWF is used.
------------------------

> And just asking out of the curiosity - are the other voltage rails
> listed in data-sheet (VD18, DDR0, VD33, VD09 and LDO1,...,LDO4) set-up
> from DT as fixed-regulators? Any reason why they are not set-up here?

TBH, I don't know why. Perhaps, the driver cannot read DDR0, LDO[1-4] values?

Best regards,
Yoshihiro Shimoda