linux-kernel - Re: [PATCH 2/4] power: supply: max17042_battery: use ModelCfg refresh on max17055

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Date:   Fri, 18 Mar 2022 20:58:24 +0100
From:   Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
To:     Hans de Goede <hdegoede@...hat.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Sebastian Reichel <sre@...nel.org>, linux-pm@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Purism Kernel Team <kernel@...i.sm>, Rob Herring <robh@...nel.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 2/4] power: supply: max17042_battery: use ModelCfg refresh on max17055

On piątek, 18 marca 2022 09:22:16 CET Krzysztof Kozlowski wrote:
> On 18/03/2022 01:10, Sebastian Krzyszkowiak wrote:
> > Unlike other models, max17055 doesn't require cell characterization
> > data and operates on smaller amount of input variables (DesignCap,
> > VEmpty, IChgTerm and ModelCfg). Input data can already be filled in
> > by max17042_override_por_values, however model refresh bit has to be
> > set after adjusting input variables in order to make them apply.
> > 
> > Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
> > ---
> > 
> >  drivers/power/supply/max17042_battery.c | 73 +++++++++++++++----------
> >  include/linux/power/max17042_battery.h  |  3 +
> >  2 files changed, 48 insertions(+), 28 deletions(-)
> > 
> > diff --git a/drivers/power/supply/max17042_battery.c
> > b/drivers/power/supply/max17042_battery.c index
> > c019d6c52363..c39250349a1d 100644
> > --- a/drivers/power/supply/max17042_battery.c
> > +++ b/drivers/power/supply/max17042_battery.c
> > @@ -806,6 +806,13 @@ static inline void
> > max17042_override_por_values(struct max17042_chip *chip)> 
> >  	    (chip->chip_type == MAXIM_DEVICE_TYPE_MAX17055)) {
> >  		
> >  		max17042_override_por(map, MAX17047_V_empty, config-
>vempty);
> >  	
> >  	}
> > 
> > +
> > +	if (chip->chip_type == MAXIM_DEVICE_TYPE_MAX17055) {
> > +		max17042_override_por(map, MAX17055_ModelCfg, config-
>model_cfg);
> > +		// VChg is 1 by default, so allow it to be set to 0
> 
> Consistent comment, so /* */
> 
> I actually do not understand fully the comment and the code. You write
> entire model_cfg to MAX17055_ModelCfg and then immediately do it again,
> but with smaller mask. Why?

That's because VChg is 1 on POR, and max17042_override_por doesn't do anything 
when value equals 0 - which means that if the whole config->model_cfg is 0, 
VChg won't get unset (which is needed for 4.2V batteries).

This could actually be replaced with a single regmap_write.

> > +		regmap_update_bits(map, MAX17055_ModelCfg,
> > +				MAX17055_MODELCFG_VCHG_BIT, 
config->model_cfg);
> 
> Can you align the continued line with previous line? Same in other
> places if it is not aligned.
> 
> > +	}
> > 
> >  }
> >  
> >  static int max17042_init_chip(struct max17042_chip *chip)
> > 
> > @@ -814,44 +821,54 @@ static int max17042_init_chip(struct max17042_chip
> > *chip)> 
> >  	int ret;
> 
> Best regards,
> Krzysztof


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