Messages in this thread | | | Date | Wed, 21 May 2014 11:25:43 -0700 | From | "Mark A. Greer" <> | Subject | Re: bq24190: What's the correct API to turn boost mode (OTG) on for the battery charger ? |
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On Fri, May 16, 2014 at 12:35:34AM +0200, Laurent Pinchart wrote: > Hi Mark, > > Thank you for the quick reply.
Hi Laurent. Sorry for the delay.
> On Thursday 15 May 2014 15:08:44 Mark A. Greer wrote: > > On Thu, May 15, 2014 at 10:29:26PM +0200, Laurent Pinchart wrote: > > > Hello, > > > > [Adding Anton Vorontsov to CC list.] > > > > Hi Laurent. > > > > > I'm trying to enable battery charging on an OMAP4 board based on a twl6030 > > > PMIC with external bq24190 battery charger and bq27510 fuel gauge. > > > > > > The system has an OTG USB port that can be used to charge the battery, and > > > that can also be used in host mode. In that case the bq24190 needs to be > > > switched to boost mode to provide the +5V power supply from the battery. > > > > > > The bq24190 has a charge configuration register field that supports charge > > > disabled, charge enabled and OTG (boost mode). The field is set by the > > > bq24190 driver in response to setting the charge type : > > > POWER_SUPPLY_CHARGE_TYPE_NONE will disable charing, and > > > POWER_SUPPLY_CHARGE_TYPE_TRICKLE and > > > POWER_SUPPLY_CHARGE_TYPE_FAST will enable it. However, OTG boost mode is > > > not supported. > > > > > > > > > The driver exposes most register fields as sysfs attributes (which doesn't > > > sound very safe to me, but that's another story). I can thus enable OTG > > > boost mode directly from userspace through the driver-specific API, but > > > that just bypasses the power supply API. I'm thus not very fond of that > > > solution. > > > > No, its not a good solution. As indicated in the commit log, the sysfs > > entries are there because there are just so many fields that don't map > > well to the existing interface. > > > > Maybe we should add support for a DT entry to enable exporting those > > fields(disabled by default)? > > > > > Possibly due to my really basic (not to say nonexistent) knowledge of the > > > power supply subsystem I haven't found an API to expose this feature. I > > > was wondering if someone had given a though regarding how to implement > > > this properly. > > > > What if we just added something like POWER_SUPPLY_CHARGE_TYPE_BOOST? > > That was actually my first thought, and I assumed it would be rejected as > boost mode is not a charge type but a discharge type :-)
Er, right. :(
> This being said, I > don't have enough experience with battery chargers to decide whether this is a > good solution. If you believe it is, I'll trust you on that.
No, you're right, that isn't a good solution.
I don't see a really good fit anywhere. The easiest thing may be to add a new POWER_SUPPLY_PROP_xxx power_supply_property member which can be set to flip it into boost mode but I'm not sure if that's really the right thing to do.
I hope Anton will comment on this.
> On a side note, is there any reference userspace implementation of a battery > manager ? The vendor BSP I've received with the board hardcodes calls to the > bq24190 in the MUSB driver to switch between OTG and trickle charge modes > based on USB cable connection/disconnection events. That's pretty ugly, and I > assume this should be handled in userspace - or is there a standard kernel > infrastructure for that ?
I don't have a good feel for what's out there but the charger-manager may be a good place to start:
Documentation/power/charger-manager.txt drivers/power/charger-manager.c
HTH,
Mark --
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