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OMAP4: CPUidle: Add coupled idle support

Santosh Shilimkar linux-arm-kernel linux-omap 1 version New

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Cover letter [PATCH 0/3] OMAP4: CPUidle: Add coupled idle support
Quoted 24 lines · Kevin Hilman

Hi Santosh,

Quoted 9 lines · Santosh Shilimkar

The series adds the coupled cpuidle support for OMAP4 based on the v2 series posted [1]. This makes OMAP4 to support SMP cpuidle and also removes the hard dependency of off-lining CPU1 to trigger deeper C-states.

I have put together a branch which is based on 3.3 kernel with Len Browns next branch [2] which has time keeping and other cpuidle patches which will mostly get merged by 3.4-rc1 and rebased coupled idle series from [1].

Thanks for rebasing this.

Quoted 2 lines

git://gitorious.org/omap-sw-develoment/linux-omap-dev.git
for_3.5/omap4_coupled_cpuidle-rebase

This branch by itself seems to work fine. However, when combining with other stuff that has merged for v3.4, it hangs during boot. I haven't yet isolated the problem, but it's easy to reproduce by combining your branch with v3.4-rc1:

Quoted 7 lines

git checkout -b test/coupled-v3.4 v3.4-rc1
git merge -s recursive -X ours santosh/for_3.5/omap4_coupled_cpuidle-rebase [1]

This hangs on boot, and it seems like a coupled state deadlock because commenting out the coupled states in the C-state creation of cpuidle44xx.c makes it boot just fine.

I managed to reproduce the issue. Just to ensure that any OMAP changes have not introduced the regression I merged all Tony's pull request on my branch and tried it out. OMAP changes are fine and coupled idle continue to work.

Started bisecting the commits. For bisect I have to create a series which is not dependent on Len's cpuidle updates. First round of bisect was not successful so tried one more time. Was very close to narrowing down on commit but then encountered set of commits where either CPUIDLE itself is broken(deeper C-states are not getting attempted) or I get softIRQ 08 pending error.

The last bad commit in bisect was ... [8682df25ca9afd3aac30f2c72d00bd98de2118e8] Merge branch 'fortglx/3.4/rtc' of git://git.linaro.org/people/jstultz/linux into timers/core

So far looks like, one of below series has introduced a race which is getting highlighted with coupled cpuidle patchset.

9b612fa Merge branch 'fortglx/3.4/clocksource' of
git://git.linaro.org/people/jstultz/linux into timers/core 8682df2 Merge branch 'fortglx/3.4/rtc' of
git://git.linaro.org/people/jstultz/linux into timers/core 97ac984 Merge branch 'fortglx/3.4/time' of
git://git.linaro.org/people/jstultz/linux into timers/core

Will try to continue the debug tomorrow. let me know if you find some thing interesting in your day time.

Regards
santosh

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