Subject: Re: [PATCH] icecube/lite5200b: wakeup from low-power support

From: Rafal Jaworowski <[email-masked]>
Date: Sat, 31 Mar 2007 19:20:19 +0200

Domen Puncer wrote:
> U-Boot part of Lite5200b low power mode support.
> Puts SDRAM out of self-refresh and transfers control to
> address saved at physical 0x0.
> 

Hi Domen,

As I understand while waking up from the low-power mode the machine is 
effectively powering on, similarly to the cold reset, so U-Boot runs 
from the beginning as usual, but after the SDRAM controller has been 
initialised we detect the wakeup and teleport to the saved DRAM address.

Since in case of a wakeup from the low-power mode we skip everything in 
U-Boot that is happening past initdram(), please clarify the following:

- are you sure there are no steps beyond init_func_ram()/board_init_f() 
that should be performed while waking up? For example:

- are all timers settings properly re-stored?

- wouldn't the host/PCI bridge need to be re-initialised and 
re-configured as part of the wakeup process? Did you happen to test some 
PCI devices and would they survive after wakeup from the the low-power 
mode? (A similar question would apply to the USB controller)

Also, a more general question: isn't time base update required after the 
wakeup, specially if it's been a long sleep?

kind regards,
Rafal