* Pavel Machek <pavel@xxxxxx> [210219 21:58]: > > > If I turn off charging with echo 0 > input_current_limit, 0.2 to 0.4A > > > is drawn from USB, and battery is not discharged: > > > > > > root@devuan-droid4:/sys/class/power_supply/usb# echo 0 > input_current_limit > > > root@devuan-droid4:/sys/class/power_supply/usb# cat current_now > > > 0 > > > > Hmm so have you measured that setting the current limit to 0 actually > > draws something from the USB? > > Yes, it does, if I do the echo when charge is done. (I have small USB > passthrough with volt and amp meters). It has been behaving weirdly in > other cases.p OK great, seems like we can just change the charger timeout then. > > I recall clearing the ichrgr bits stops the vbus draw completely, but > > I could be wrong. > > > > > Is that a better way to handle full battery? > > > > We could experiment with switching over to usb power when the battery is > > full. Looking at the docs for mc1378 it might be possible that setting > > CPCAP_REG_CRM_FET_OVRD and clearing CPCAP_REG_CRM_FET_CTRL after the > > battery is full disables charging but still keep drawing power from > > the usb. I'd assume the current limit still needs to be nonzero there > > too? Totally untested.. > > I may be able to test patches... Yeah this too might be worth testing on some donor device.. > > And switching back to battery power on usb disconnect will potentially > > only give us very little time based on the different line length for > > vbus and ground pins compared to data pins on the usb connector.. And > > uvos had some concerns about the battery capacity putting it back online, > > so adding him to Cc also. > > You mean, we'd have to take interrupt and switch registers in order to > switch back to battery power, and system would crash if we did not > make it in time? Yes hopefully we don't need to do that. My guess is we should find some FET_OVRD and FET_CTRL setting we can always keep enabled after charger negotation. Maybe we already have the right settings based on your tests :) Regards, Tony
