Hi, On Thu, 2007-11-29 at 10:29 +0100, ext Frantisek Dufka wrote: > Austin Che wrote: > > > > I actually had been looking at back-porting kexec into the 2.6.18 > > kernel. > > Might be worth trying too, see below > > > But I just recompiled 2.6.21 with kexec on and patched > > kexec-tools with arm patches and it does not work for me (the > > screen just goes blank and eventually the whole device > > reboots). kexec seems to be really quite simple (code-wise) and so > > I can't imagine it being that difficult to figure out for someone > > with a clue about omap. > > I would expect at least two problems: > > - passing right data (set of tagged structures) that comes from > bootloader to new kernel, these are at specific physical address at boot > time of first kernel but I think they get freed and overwritten later. > > - setting hardware back to some harmless state so new kernel can > initialize it again properly. This could be quite tricky for OMAP. Best > for this it to kexec new kernel as early as possible before full system > boot initializes dsp, audio, wlan, bt, camera ... Maybe even some stub > kernel with everything uneeded stripped off could improve chances. > > As for booting 2.6.18 from 2.6.21 one problem may be advanced frequency > and voltage scaling which is not present in 2.6.18. Might be worth > trying to force CPU clock to 333 (which will hopefully set also other > clocks and paremeters correctly) before kexec-ing older kernel so 2.6.18 > won't be surprised too much. The frequency scaling is enabled only after the kernel has booted, the default OP is 330MHz, so that shouldn't come in the way. But I wonder if chrooting wouldn't be better: then one could for example run OS2008 from OneNAND and OS2007 from MMC simultaneously and have only those apps that are not available yet for OS2008 to run in the chrooted environment and access the screen simultaneously through X. This is just a thought I had right now, so I don't know how feasible it would be, but might be simpler to try. -- Cheers, Igor Igor Stoppa <igor.stoppa at nokia.com> (Nokia Multimedia - CP - OSSO / Helsinki, Finland)
