linux-kernel - Re: [PATCH 2/2] power_supply: Add support for TI BQ25890 charger chip

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Date:	Tue, 19 May 2015 19:03:40 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Laurentiu Palcu <laurentiu.palcu@...el.com>
Cc:	Krzysztof Kozlowski <k.kozlowski@...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>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH 2/2] power_supply: Add support for TI BQ25890 charger chip

2015-05-19 18:14 GMT+09:00 Laurentiu Palcu <laurentiu.palcu@...el.com>:
> Hi Krzysztof,
>
> On Tue, May 19, 2015 at 05:40:25PM +0900, Krzysztof Kozlowski wrote:
>> > +
>> > +static int bq25890_chip_reset(struct bq25890_device *bq)
>> > +{
>> > +       int ret;
>> > +
>> > +       ret = bq25890_field_write(bq, F_REG_RST, 1);
>> > +       if (ret < 0)
>> > +               return ret;
>> > +
>> > +       do {
>> > +               ret = bq25890_field_read(bq, F_REG_RST);
>> > +               if (ret < 0)
>> > +                       return ret;
>> > +
>> > +               usleep_range(5, 10);
>> > +       } while (ret == 1);
>>
>> Is it possible to loop here indefinetely?
> According to specifications, this field is "Reset to 0 after register
> reset is completed", so I'm trusting the chip will behave as advertised!
> :) We could implement a safety mechanism to avoid looping in case the
> chip misbehaves but I don't think it's worth it. What do you think?

I just prefer to use some retry counter because it would be better to
fail the reset instead of being stuck here. The chip may behave
correctly but still a bug could exist in the driver. The retry counter
won't be much complicated here also. But I do not insist so if you
really think it is not worth it then I am fine.

Best regards,
Krzysztof
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