Management of Power Management ;)

Svetoslav Trochev sal_electronics at
Thu Aug 20 01:22:18 CEST 2009

Paul Fertser wrote:
> We tried to coordinate some effort at #openmoko irc channel. The guys
> who have the device and abilities are: Psi, Kero and
> SpeedEvil. Unfortunately, they lack time to do any serious
> investigations.
Thanks Paul for the info I will keep eye for those nicknames in the
list. Unfortunately I don't have access to the IRC from work and my
tenable English makes me useless on any real time chat, but gives me
some time to think on the problem! :)
> I'm getting a gta01 soon so i very much hope i'll be able to do
> something wrt power consumption (the main goal of getting a gta01 for
> me). The plan is so far to physically cut (by removing 0Rs) most
> consumers and analise step by step all kernel and hardware problems.
> Do not hold your breath though.
> BTW, for a start you can fix SD power control issues (due to a bad
> merge the function got fubarred), if you run with SD inserted you'll
> have extra ~20mA feeding card even in suspend.
Well I just looked the GTA01 schematics and SD card interface an found
first design problem. ;) It can only account for ~30uA leaking from the
IO_3V3 power bus to SD_3V3 power bus through R7501 and R7502 when U7501
is off. I believe we are missing blocking diode that will prevent
current to flow between SD and IO power buses. (I don't remember if the
simple diode can stop 30uA leak. )
Of course you are talking about ~20mA so I guess the problem is in the
kernel that keeps the power to the SD card on at all time. Right? (
Signal /SD_ON coming from pin M14 on S3C2410X ).

Best regard,

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