linux-kernel - Re: [PATCH v7 2/5] power: max77843_charger: Add Max77843 charger device driver

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Date:	Mon, 09 Mar 2015 13:13:19 +0100
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Beomho Seo <beomho.seo@...sung.com>
Cc:	Lee Jones <lee.jones@...aro.org>,
	Sebastian Reichel <sre@...nel.org>,
	Jaewon Kim <jaewon02.kim@...sung.com>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-input@...r.kernel.org,
	Inki Dae <inki.dae@...sung.com>,
	SangBae Lee <sangbae90.lee@...sung.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [PATCH v7 2/5] power: max77843_charger: Add Max77843 charger
 device driver

On pon, 2015-03-09 at 20:46 +0900, Beomho Seo wrote:
> On 03/09/2015 08:02 PM, Krzysztof Kozlowski wrote:
> > 2015-03-09 1:35 GMT+01:00 Beomho Seo <beomho.seo@...sung.com>:
> >> On 03/08/2015 05:13 AM, Sebastian Reichel wrote:
> >>> On Mon, Mar 02, 2015 at 07:10:35PM +0900, Jaewon Kim wrote:
> >>>> From: Beomho Seo <beomho.seo@...sung.com>
> >>>>
> >>>> This patch adds device driver of max77843 charger. This driver provide
> >>>> initialize each charging mode(e.g. fast charge, top-off mode and constant
> >>>> charging mode so on.). Additionally, control charging paramters to use
> >>>> i2c interface.
> >>>>
> >>>> Cc: Sebastian Reichel <sre@...nel.org>
> >>>> Signed-off-by: Beomho Seo <beomho.seo@...sung.com>
> >>>
> >>> Reviewed-By: Sebastian Reichel <sre@...nel.org>
> >>>
> >>> I can't take it as is, since it depends on the private header file
> >>> of PATCHv1.
> >>>
> >>> -- Sebastian
> >>>
> >>
> >> This patch reviewed by Sebastian.
> >> Could you Please merge that your git tree ?
> > 
> > Hi,
> > 
> > ... and again we are adding a new driver for very similar chipset to
> > already supported. I looked at spec and the charger's registers are
> > almost the same as for max77693. Their layout and addresses are the
> > same. I see some minor differences, probably the most important would
> > be different values current (fast-charge, top-off). But still 90% of
> > registers are the same... Do we really have to add new driver?
> > 
> > Best regards,
> > Krzysztof
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-input" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > 
> 
> Hi,
> 
> Thank you for your comment. As you say, both chip set are similar.
> But new driver need for support max77843. It is support different below
> - Provide Battery presence information.

Another set of power supply properties could be added for that chip.
This way the get_property() function would be the same but actually the
POWER_SUPPLY_PROP_PRESENT won't be called for max77693.

> - Can OTG FET control.

Where the OTG FET feature is it enabled in your driver? I couldn't find
it.

> - Bigger Fast charge current, Top Off current Threshold selection.
> - Various and bigger OTG current limitation.
> - Bigger primary charger termination voltage setting.
> - Different maximum input current limit selection(Different step).

Yes, I mentioned some of these differences (the Fast/top-off
differences). These are differences in values so it does not require new
driver. There is need to develop new driver just to support different
current (3.0 A instead of 2.1 A) or voltage threshold.

So the only new feature - battery presence - can be easily added to
existing driver. The driver can be extended for different
current/voltage values. Such extension may even be beneficial for new
Maxim MUIC/PMIC chipsets.


Best regards,
Krzysztof

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