[PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start
lorenzo.pieralisi at arm.com
Mon Jun 9 15:38:31 PDT 2014
On Mon, Jun 09, 2014 at 06:03:31PM +0100, Doug Anderson wrote:
> Cold boot and resume from suspend are detected via various special
> flags in various special locations. Resume from suspend looks at
> INFORM1 (0x10048004) for flags. This register is 0 during a cold boot
> and has special values set by the kernel at resume time.
> It also looks as if some code looks at 0x10040900 (PMU_SPARE0) to help
> tell initial cold boot and secondary CPU bringup.
Ok, thanks a lot. It looks like firmware paths should be ready to
detect cold vs warm boot, and hopefully do not rely on a specific
MPIDR to come up first out of power states.
> > I am asking to check if on this platform CPUidle (where the notion of
> > primary CPU disappears) has a chance to run properly.
> I believe it should be possible, but we don't have CPUidle implemented
> in our current system. Abhilash may be able to comment more.
I am interested in more insights, that's very helpful thanks.
> > Probably CPUidle won't attain idle states where IRAM content is lost, but I
> > am still worried about the primary vs secondaries firmware boot behaviour.
> I don't think iRAM can be turned off for CPUidle.
It might be added a system state but I doubt that too and if you are
relying on registers for jump addresses that's not even a problem in
the first place.
> > What happens on reboot from suspend to RAM (or to put it differently,
> > what does secure firmware do on reboot from suspend to RAM - in
> > particular how is the "jump" address to bootloader/kernel set ?)
> Should be described above now.
Thank you very much.
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