[LinuxBIOS] Fast path resume, high-level design
rminnich at gmail.com
Fri May 4 05:17:57 CEST 2007
On 5/3/07, Peter Stuge <stuge-linuxbios at cdy.org> wrote:
> On Thu, May 03, 2007 at 05:55:39PM -0400, Jim Gettys wrote:
> > Mitch wrote a fast path resume from RAM for the OLPC Geode
> > hardware.
> The fastest path is obviously attractive also in LinuxBIOS.
> > Once you've done that, you find that you've done just about
> > everything to initialize the hardware in the first place; so that
> > code is now used both at boot time and at suspend from RAM time.
> This is an interesting observation.
> Perhaps all chip init would best be written in some macro language?
> (one specific for the task?)
We've talked about this. It only really works on OLPC because OLPC is
so incredibly simple. Add an opteron of the type that stefan used to
port to -- variable number of CPUs, 31 PCI busses, etc. etc. -- and
it's a bit harder.
Also, let's pretend that someday there is an OLPC with SPD. The
problem starts to get ugly again as you add back in SMBUS support,
etc. etc. -- all that stuff that linuxbios can do pretty well.
I also still believe, having watched how things played out, that I
want linux as my bios. Nothing in what I have seen on OLPC changes my
belief, and some things that have happened on OLPC strongly confirm
Again, the OLPC code can be found at openbios.org, it's pretty
trivial, and works mainly because the OLPC hardware has hardcoded dram
timing, etc. etc. And, as Jordan pointed out, things can fall apart
when some of these constants change.
There's no clear answer yet.
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