[U-Boot-Users] [PATCH] icecube/lite5200b: wakeup from low-power support
raj at semihalf.com
Sat Mar 31 19:20:19 CEST 2007
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.
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?
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