Re: [PATCH] mfd: add bq2415x charger driver

[Pali Rohár]

Hi,

On Tuesday 06 December 2011 04:49:37 you wrote:
> Hi,
>
> 2011/12/6 Sebastian Reichel <sre@xxxxxxxxxx>:
> > Good to hear somebody is working on this :) I planned to do this
> > myself, but didn't find any time for it. Here are some comments
> :
> > from me:
> :)
> :
> > [...]
> >
> >> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> >
> > I would expect the driver in drivers/power. But maybe MFD is
> > better, since the chip can also be used to power USB host?

Yes, chip support usb host mode and is working on rx51.

>
> Perhaps, at least I haven't tried that.
>
> > [...]
> >
> >> +#define BQ2415X_VOLTAGE_SCALE 20000
> >
> > If I remember correctly (I read the specs some time ago), this can
> > be configured via external resistor. So this is board specific?
>
> Not really. There are 6 bits: 640, 320, 160, 80, 40, 20. So values
> from 0 to 1260mV can be represented, at steps of 20mV. A value of 0
> means 3.5V.
>
> > [...]
> >
> >> +     bq2415x_i2c_write(cli, BQ2415X_CHG_CTL, 0x42);
> >> +     bq2415x_set_voltage(cli, 0, 4200000);
> >> +     bq2415x_set_current_limit(cli, 1800000, 1800000);
> >
> > So it always charges with 1.8A? Shouldn't this be dependent on the
> > input source (e.g. 500mA from USB)? Also what's if no charger is
> > connected at all?
>
> No. I'm hard-coding those values, but I wrote the functions
> (set_voltate, set_current_limit) so all values are supported.

These hardcoded values should go to board specified section.

>
> What is missing is the code to connect this driver to the charger
> detector driver (isp1704), so those values are determined dynamically.
>
> > Apart from this I think those values should be exposed to sysfs
> > via /sys/class/power_supply.
>
> Perhaps. Although I don't see much of the power supply interface that
> could be useful here, but if so, I guess this should be indeed in
> 'drivers/power'.

Power supply interface has pending patches for chargers. Patches will add
interface for periodic calling functions - which is usefull for watchdog reset
and charging (+ errors handling).

>
> Cheers.

--
Pali Rohár
pali.rohar@xxxxxxxxx

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