[PATCH 1/1] uboot-pcf50633-default-curr-lim-1A.patch

[Harald Welte]

On Thu, Feb 21, 2008 at 08:21:17AM +0800, Andy Green wrote:
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> Somebody in the thread at some point said:
> > Somebody in the thread at some point said:
> > 
> >>> 1) Stop PMU killing us if we don't have a battery in (by setting default
> >>>     current limit to 1A)
> > 
> >> that this code is _never_ put onto any production / 'sold' devices.  You
> >> cannot draw more than 100mA from USB without being configured by the
> > 
> > Well, it's a good point, but currently we pull more than 100mA just
> > waking up from the USB-no-battery case in order to make a negotiation
> > for > 100mA... er...
> 
> Yeah this is the case, so we can't meet this without doing wakeup
> sequencing in a more controlled way and spending time there.
> 
> If I leave that limit to 100mA with no battery in the device fails to
> start up fully since it needs more than 100mA to get going with LCM up
> and trips the limit, causing reboot or shutdown early in U-Boot.  With a
> battery in its fine since the battery is leaned on for the balance.
> 
> I found it works fine at a 500mA limit which is compatible with overall
> USB power availability, so I changed it back to that and will send a
> patch for the patch in a moment, thanks for pointing out the badness of
> the 1A choice.  For the badness of the 500mA choice, point taken but
> this'll do for now until we can actually cope with 100mA limit.

I think this is what I would call a serioous 'quality of implementation
issue'.

Not that I have anything to say in this project anymore, but it would
basically resort to the same kind of low quality level that originally
we at least always tried to differentiate us from.

I would actually phrase it as the 'linux vs. pragmatism' attitude, where
we do something either right, or we don't do it.

My take on this is:

If the product cannot ensure to be within the current limits as per USB
spec in a certain setup (e.g. no battery inserted), then it should not
work in that setup at all.  There is no imminent need forcing it to work
without a battery.  If somebody gets around fixing the software to
handle this correctly later on, it can be enabled.

-- 
- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
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