[Gta04-owner] Sporadic USB charging issue identified

Dr. H. Nikolaus Schaller hns at goldelico.com
Wed Feb 20 08:47:12 CET 2013

Am 20.02.2013 um 07:55 schrieb Andreas Kemnade:

> On Wed, 20 Feb 2013 08:22:07 +1100
> NeilBrown <neilb at suse.de> wrote:
>> On Tue, 19 Feb 2013 09:25:07 +0100 Dr.H.Nikolaus Schaller <hns at goldelico.com>
>> wrote:
>>> So how do we get a good solution into the drivers?
>> I find it easier to think about solutions when I know exactly what is
>> currently happening.
>> So I would add some printk in the various interrupt handlers so that we know
>> exactly what interrupts happen when, and what values are in the relevant
>> registers at that time.
> There are even enough debug printk which just wait do be enabled...
> Just keep in mind another scenario: I found that there are many usb
> cables with underdimenioned power lines. So you'll have a voltage drop
> below the VBUSUNPLGEN/VBUSVT threshold when charging with full 600mA.

Yes, that is the key scenario I am looking for a solution.

The charger autonomously decided to resign by VBUSUNPLGEN=1 (which is not monitored by software).
And since the OTG system thinks that VBUS is still available it does not see a necessity to restart charging.


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