[PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start
chander.kashyap at linaro.org
Tue Jun 10 01:12:11 PDT 2014
On 10 June 2014 04:08, Lorenzo Pieralisi <lorenzo.pieralisi at arm.com> wrote:
> 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.
Cpuidle is implemented for exynos5420, and is tested on chromebook.
> 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.
Yes thats true.
> 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.
> To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
with warm regards,
More information about the linux-arm-kernel