[PATCH] qi: initialize PMU GPIOs

Andy Green andy at openmoko.com
Sat Jan 24 18:10:13 CET 2009

Hash: SHA1

Somebody in the thread at some point said:
| Andy Green wrote:
|> Another issue though is that for determinism, really the kernel driver
|> should arguably assert all the needed state for the default at kernel
|> startup and not leave it to be inherited by the bootloader as we have
|> previously done.
| How about taking the next step and redoing all the PMU and GPIO setup
| in mach-gta02.c or similar ? I've been suggesting this for a long time,
| but you didn't like the idea back then.

It's not the "next step" but exactly what I wrote.

What did you actually suggest "a long time" ago?  NOR U-Boot action is
an obvious fly in the ointment.

| That way, the kernel doesn't care what the boot loader did or didn't
| do, and anyone who wants to understand the logic behind the use of
| some signal has fewer places to look at for answers.

It does though increase the number of times when there is temporary
possibility of different state in the hardware.

~ - post reset and NOPOWER hard state
~ - post-reset with power hard state
~ - post-bootloader changes (which does not set all state)
~ - post-kernel changes (which does not set all state either)

| This still leaves the time until the kernel comes up susceptible to
| such problems, we could improve that a little by sharing the code,
| e.g., qi could use the defaults from the kernel. That would create a
| build-time dependency, which isn't great but probably bearable, and
| it would make kernel and boot loader automatically converge.

No it's death to try to tie one of three bootloaders that can be in use
to kernel patchlevel.

|> Really the defaults in hardware should be designed to
|> be sane already (ie, pull that line down not up) so the bootloader is
|> not involved.
| Ah, in a perfect world without backup batteries and things that reset
| only in NoPower but not in Standby ... ;-)

The pullup is just wrong regardless of PMU private state :-)

- -Andy
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