Re: [PATCH 1/2] ARM: cpuidle: fix !cpuidle_ops[cpu].init case during init

From: Daniel Lezcano
Date: Wed Mar 30 2016 - 05:31:47 EST

On 03/30/2016 10:43 AM, Jisheng Zhang wrote:
On Wed, 30 Mar 2016 10:41:09 +0200 Daniel Lezcano wrote:

On 03/30/2016 10:17 AM, Jisheng Zhang wrote:
On Wed, 30 Mar 2016 10:09:12 +0200 Daniel Lezcano wrote:

On 03/30/2016 09:16 AM, Jisheng Zhang wrote:
Hi Daniel,

[ ... ]

Added Lorenzo and Catalin.

Hi Jisheng,

this should be handled in the arm_cpuidle_read_ops function.

Thanks for reviewing. After some consideration, I think this patch isn't correct
There may be platforms which doesn't need the init member at all, although
currently I don't see such platforms in mainline, So I'll drop this patch
and send out one v2 only does the optimization.

There is an inconsistency between ARM and ARM64. The 'cpu_get_ops', the
arm_cpuidle_read_ops from the ARM64 side, returns -EOPNOTSUPP when the
init function is not there for cpuidle.

arm64's arm_cpuidle_init() returns -EOPNOTSUPP if init callback isn't defined

I don't think it is a problem, but as ARM/ARM64 are sharing the same
cpuidle-arm.c driver it would make sense to unify the behavior between
both archs.

yes, agree with you. From "unify" point of view, could I move back the suspend
callback check and init callback check into arm_cpuidle_init() for arm as V1 does?

Why ? To be consistent with ARM64 ?

Yes, that's my intention.

Well, I don't have a strong opinion on that. ARM64 cpu_ops is slightly different from cpuidle_ops as the cpu boot / hotplug operations are placed in a different place and that explains why on ARM64 we can have an successful 'get_ops' because we use the partially filled structure. On ARM, it is cpuidle_ops only, so we can gracefully fail if the ops are not defined.

IMO, it still make sense to keep the checks in arm_cpuidle_read_ops for ARM.

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