[Ksummit-discuss] [TECH TOPIC] mobile phones

[Sebastian Reichel]

On Tue, Jun 27, 2017 at 11:57:55PM +0200, Pavel Machek wrote:
> Hi!
> 
> > > Boot your notebook with init=/bin/bash, and launch fsck on low
> > > battery. It will blink, it may beep, but in the end it will power off
> > > abruptly at maybe 3.6V per cell, before battery is damaged. Now try
> > > the same on N900. It will not blink, and it will run battery down to
> > > less then 3.0V; various components will fail, you'll get screen
> > > flicker, and presumably your MMC will be _really_ unhappy. Eventually,
> > > CPU fails, machine reboots, and machine will attempt to do _the same
> > > again_.
> > > 
> > > Basically we are missing one layer of protection here, compared to the
> > > PC case.
> > 
> > It should be fine to add something like Tony's orderly_poweroff to
> > the rx51 battery driver.
> 
> Yep, I actually have a patch for that. Needs some cleanups, but if it
> is basically acceptable, there's no problem doing them. Aha, and
> probably breaks boot or something, that's why I disable it. But you
> should get the idea...
> 
> > > Problem is that bootloader does not even know about battery charging,
> > > and is far from having required drivers. That's why I'd try to get
> > > buy-in ;-).
> > 
> > Actually Nokia Loader does know about battery charging and does so
> > for really empty batteries. Once the battery is full enough it tries
> > to boot operating system with better monitoring capabilities,
> > though.
> 
> 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?

> > > It is not perfect, indeed.
> > > 
> > > So we currently have GPSes on serial, producing NMEA. Gpsd there may
> > > be good enough. But then we have different hardware, not producing
> > > NMEA (GPS on N900 is exposed as network packet over PHONET
> > > interface, there's drivers/usb/serial/garmin_gps.c with who-knows-what
> > > interface)... and it would be nice to have good, "native" GPS
> > > interface which would work in this case. (We'd like timestamps for
> > > incoming data and lat/long/alt + speed in lat/long/alt + error in
> > > lat/long/alt sampled at the same time, at the very least).
> > > 
> > > Its similar to mice, really. We used to have gpm, now we have real
> > > drivers.
> > > 
> > > Plus there's still issue of AGPS data upload.
> > 
> > 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).

> 
> Best regards,
> 								Pavel
> 
> 
> diff --git a/drivers/power/supply/bq27xxx_battery.c b/drivers/power/supply/bq27xxx_battery.c
> index 398801a..db9c69e 100644
> --- a/drivers/power/supply/bq27xxx_battery.c
> +++ b/drivers/power/supply/bq27xxx_battery.c
> @@ -52,6 +52,7 @@
>  #include <linux/delay.h>
>  #include <linux/platform_device.h>
>  #include <linux/power_supply.h>
> +#include <linux/reboot.h>
>  #include <linux/slab.h>
>  #include <linux/of.h>
>  
> @@ -808,11 +809,9 @@ static inline int bq27xxx_read(struct bq27xxx_device_info *di, int reg_index,
>  static int bq27xxx_battery_read_soc(struct bq27xxx_device_info *di)
>  {
>  	int soc;
> +	bool single = di->chip == BQ27000 || di->chip == BQ27010;
>  
> -	if (di->chip == BQ27000 || di->chip == BQ27010)
> -		soc = bq27xxx_read(di, BQ27XXX_REG_SOC, true);
> -	else
> -		soc = bq27xxx_read(di, BQ27XXX_REG_SOC, false);
> +	soc = bq27xxx_read(di, BQ27XXX_REG_SOC, single);
>  
>  	if (soc < 0)
>  		dev_dbg(di->dev, "error reading State-of-Charge\n");
> @@ -876,11 +875,9 @@ static inline int bq27xxx_battery_read_fcc(struct bq27xxx_device_info *di)
>  static int bq27xxx_battery_read_dcap(struct bq27xxx_device_info *di)
>  {
>  	int dcap;
> +	bool single = di->chip == BQ27000 || di->chip == BQ27010;
>  
> -	if (di->chip == BQ27000 || di->chip == BQ27010)
> -		dcap = bq27xxx_read(di, BQ27XXX_REG_DCAP, true);
> -	else
> -		dcap = bq27xxx_read(di, BQ27XXX_REG_DCAP, false);
> +	dcap = bq27xxx_read(di, BQ27XXX_REG_DCAP, single);
>  
>  	if (dcap < 0) {
>  		dev_dbg(di->dev, "error reading initial last measured discharge\n");
> @@ -1061,10 +1058,10 @@ static int bq27xxx_battery_read_health(struct bq27xxx_device_info *di)
>  	/* Unlikely but important to return first */
>  	if (unlikely(bq27xxx_battery_overtemp(di, flags)))
>  		return POWER_SUPPLY_HEALTH_OVERHEAT;
> -	if (unlikely(bq27xxx_battery_undertemp(di, flags)))
> -		return POWER_SUPPLY_HEALTH_COLD;
>  	if (unlikely(bq27xxx_battery_dead(di, flags)))
>  		return POWER_SUPPLY_HEALTH_DEAD;
> +	if (unlikely(bq27xxx_battery_undertemp(di, flags)))
> +		return POWER_SUPPLY_HEALTH_COLD;
>  
>  	return POWER_SUPPLY_HEALTH_GOOD;
>  }
> @@ -1122,6 +1119,49 @@ void bq27xxx_battery_update(struct bq27xxx_device_info *di)
>  }
>  EXPORT_SYMBOL_GPL(bq27xxx_battery_update);
>  
> +static void shutdown(char *reason)
> +{
> +	pr_alert("%s Forcing shutdown\n", reason);
> +	orderly_poweroff(true);
> +}
> +
> +static int generic_protect(struct power_supply *psy)
> +{
> +	union power_supply_propval val;
> +	int res;
> +	int mV, mA, mOhm = 430, mVadj = 0;

430 mOhm?

> +	res = psy->desc->get_property(psy, POWER_SUPPLY_PROP_HEALTH, &val);
> +	if (res)
> +		return res;
> +
> +	if (val.intval == POWER_SUPPLY_HEALTH_OVERHEAT)
> +		shutdown("Battery overheat.");
> +	if (val.intval == POWER_SUPPLY_HEALTH_DEAD)
> +		shutdown("Battery dead.");
> +
> +	res = psy->desc->get_property(psy, POWER_SUPPLY_PROP_VOLTAGE_NOW, &val);
> +	if (res)
> +		return res;
> +	mV = val.intval / 1000;
> +
> +	if (mV < 2950)
> +		shutdown("Battery below 2.95V.");
> +
> +	res = psy->desc->get_property(psy, POWER_SUPPLY_PROP_CURRENT_NOW, &val);
> +	if (res)
> +		return res;
> +	mA = val.intval / 1000;
> +	mVadj = mV + (mA * mOhm) / 1000;
> +
> +	if (mVadj < 3150)
> +		shutdown("Battery internal voltage below 3.15V.");
> +	
> +	printk(KERN_INFO "Main battery %d mV, internal voltage %d mV\n",
> +	       mV, mVadj);

s/internal voltage/open circuit voltage/g?

> +	return 0;
> +}
> +
>  static void bq27xxx_battery_poll(struct work_struct *work)
>  {
>  	struct bq27xxx_device_info *di =
> @@ -1129,6 +1169,7 @@ static void bq27xxx_battery_poll(struct work_struct *work)
>  				     work.work);
>  
>  	bq27xxx_battery_update(di);
> +	//generic_protect(di->bat);
>  
>  	if (poll_interval > 0)
>  		schedule_delayed_work(&di->work, poll_interval * HZ);
> @@ -1226,8 +1267,8 @@ static int bq27xxx_battery_capacity_level(struct bq27xxx_device_info *di,
>  }
>  
>  /*
> - * Return the battery Voltage in millivolts
> - * Or < 0 if something fails.
> + * Set val->intval to the battery Voltage in millivolts.
> + * Return < 0 if something fails.
>   */
>  static int bq27xxx_battery_voltage(struct bq27xxx_device_info *di,
>  				   union power_supply_propval *val)
> 

-- Sebastian
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