dont-smoke.patch (draw only 100mA in u-boot)

andrzej zaborowski balrogg at gmail.com
Tue Mar 25 03:28:25 CET 2008


Hi,

On 09/03/2008, Andy Green <andy at openmoko.com> wrote:
>  > This patch makes u-boot only draw up to 100mA from a USB port, unless
>  > there's an indication that it can get more. I've also simplified the
>  > code a bit.

I thought it might be useful for a user to manually provide such an
indication if the user knows that the port provides 500mA but doesn't
want her neo to do the full negotiation.  This indication could be a
combination of the hw key events or something else.  I didn't get to
implementing it yet.

>
> Why do we still have charging logic in U-Boot at all?
>
>  Are we planning on having charging logic in this minimal bootloader that
>  is to replace U-Boot?

Actually that's not such a bad place for a minimal charging logic.
Suppose your battery is completely flat and you want to charge as fast
as possible, take the GPS and go on a trip.  As fast as possibly would
be achieved by waking the cpu up for only a moment to tell the PMU to
draw 500mA and powering-off.

The issue with running with no battery and risking damaging the
upstream port (in the time between power-on and usb driver start)
could be handled similarly: normally not supported but we would allow
the user to say "do what I say" and boot on USB power.
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