Re: [Ksummit-discuss] [TECH TOPIC] mobile phones

[Sebastian Reichel <sre@kernel.org>]

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Hi,

On Wed, Jun 28, 2017 at 11:10:08PM +0200, Pavel Machek wrote:
> > > So to be exact... u-boot does not know about battery charging. And
> > > NoLo can only do very, very slow charging.
> > 
> > Yes. The idea is, that normally NoLo only charges far enough, that
> > Linux can be booted.
> > 
> > > Yes, unfortunately that does not work quite well here. Voltage goes
> > > too low before Linux can boot, so it resets, but it is still high
> > > enough for the bootloader, so it attempts to boot Linux one more time,
> > > but battery is empty and voltage goes too low before Linux can boot, ...
> > 
> > I guess your battery is not the fittest anymore?
> 
> I guess that's one issue. (One of my batteries is actually so bad that
> GSM modem fails with it.)
> 
> Well, I guess Debian boots a little longer than Maemo. Plus, I believe
> we should charge the battery from kernel by default; it will enable
> running fsck etc, and it will mean slow userspace boot will not
> break...

That sounds like really bad battery :)

> > > > On N950 there is an unsupported gps connected via i2c iirc (with
> > > > unknown protocol that needs to be RE'd) and TI's WiLink provides
> > > > GPS on a shared UART link with bluetooth-style header using yet
> > > > another protocol. I agree, that we should have a GPS subsystem.
> > > 
> > > Two GPSes in one box, interesting design. Are both of them connected
> > > to useful antenna?
> > 
> > Actually there are probably 3 GPS implementations in Droid 4:
> > 
> >  * WL1285
> >  * MDM6600 modem
> >  * LTE modem
> > 
> > As far as I understand it modems are required to have GPS access in
> > US. I'm not yet sure which of the implementations is used by Droid 4's
> > stock system, but Motorola explicitly added a driver for the WL1285 GPS
> > making it a likely candidate (The userspace part is a closed source
> > shared object used by Android).
> 
> Interesting :-). I guess you could do really fair comparison of the
> chipsets.
> 
> (Binary driver -- bad Motorola :-( )

Yeah :( Note, that Nokia also has binary driver for the N900 (which
had been reverse engineered) and a different on on N950 (which has
not been reverse engineered so far).

> > > +static int generic_protect(struct power_supply *psy)
> > > +{
> > > +	union power_supply_propval val;
> > > +	int res;
> > > +	int mV, mA, mOhm = 430, mVadj = 0;
> > 
> > 430 mOhm?
> 
> Yes, 0.43 Ohm.

What's the source of this value?

-- Sebastian

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