Re: Question about Odroid XU4 cpuidle

[Krzysztof Kozlowski <krzk@kernel.org>]

On Wed, Jun 10, 2020 at 02:18:12PM +0100, Lukasz Luba wrote:
> Hi Krzysztof, Bartek,
> 
> I recall that you have been working on some cpuidle code for Exynos(4?).
> 
> I have a question regarding CPUIdle driver for Odroid XU4.
> I use the board with LISA tests for EAS, but missing at
> least idle state 0 cause errors (please see the log below).
> 
> Currently the system does not report any idle driver and the state 0
> is missing in: /sys/devices/system/cpu/cpu0/cpuidle/state0/

The state 0 long time ago was WFI. It was kind of meaningless so it it
was dropped.

> 
> I am using driver CONFIG_ARM_BIG_LITTLE_CPUIDLE but the
> boot stops silently while trying to init the cpu idle devices in there.
> I carry on with a workaround that just removes idle state[1] and set
> state_count=1 in the big and little structures.

Try earlyprintk.

In general, the big-little cpuidle driver should work... or rather: long
time ago it was working.  It requires proper support from early stages
(BL1, secure monitor) but this should be already in standard Odroid.

I just saw there:
	/* Start at index 1, index 0 standard WFI */
so maybe it was not updated properly to removal of WFI?

I think no one uses this driver so it might be not well tested and not
that useful.

Best regards,
Krzysztof