Re: power management on embedded linux?

On Sun, 27 May 2007 05:25:08 -0400 cpope <cepope@xxxxxxxxx> wrote:
|
| <phil-news-nospam@xxxxxxxx> wrote in message
| news:f3b0i932csa@xxxxxxxxxxxxxxxxxxxx
|> On Fri, 25 May 2007 06:56:19 -0400 cpope <cepope@xxxxxxxxx> wrote:
|>
|> | Does anyone have experience with power management on embedded linux
| systems?
|> | Is it mature and working? I specifically need my platform to do a
| hibernate
|> | where the system state is saved to a ram disk and then restored very
| quickly
|> | to wake up.
|>
|> How is a ram disk going to help? Did you put the ram disk in a special
|> part of ram that won't be powered down? Or did you mean something other
|> than ram disk?
|>
|> --
|>
| |---------------------------------------/----------------------------------|
|> | Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below
| |
|> | first name lower case at ipal.net / spamtrap-2007-05-26-2312@xxxxxxxx
| |
|>
| |------------------------------------/-------------------------------------|
|
|
| Yes, the sdram will remain powered. Everything else, including fpga, will be
| shutdown.

Then I guess the ram would be a suitable place ... if there is enough of
it to save the state with. You should be sure that a sufficient area is
reserved. Making a ramdisk ahead of time would certainly be a way to do
it. The rest of it, unfortunately, I don't have experience with (how to
detect the power going down, save the state, detect power coming back on,
and restore that state). Is the CPU itself powered down? If so, then it
will have to go through some kind of startup sequence that would have to
verify that a valid state is saved. Checksumming the saved state with an
MD5 code would be a good idea if there is enough CPU time available to do
that, or if the CPU itself does the power off final step.

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-05-27-0830@xxxxxxxx |
|------------------------------------/-------------------------------------|
.

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