Re: [PATCH V5 0/8] cpuidle/ppc: Enable deep idle states on PowerNV

From: Preeti U Murthy <hidden>
Date: 2014-01-16 02:20:55
Also in: linux-pm, lkml

Hi Paul,

On 01/15/2014 08:59 PM, Paul Gortmaker wrote:

On 14-01-15 03:07 AM, Preeti U Murthy wrote:

[...]

quoted

This patchset is based on mainline commit-id:8ae516aa8b8161254d3,  and the

I figured I'd give this a quick sanity build test for a few
configs, but v3.13-rc1-141-g8ae516aa8b81 seems too old; Ben's
ppc next branch is at v3.13-rc1-160-gfac515db4520 and it fails:

-------
$ git am ppc-idle
Applying: powerpc: Free up the slot of PPC_MSG_CALL_FUNC_SINGLE IPI message
Applying: powerpc: Implement tick broadcast IPI as a fixed IPI message
Applying: cpuidle/ppc: Split timer_interrupt() into timer handling and interrupt handling routines
error: patch failed: arch/powerpc/kernel/time.c:510
error: arch/powerpc/kernel/time.c: patch does not apply
Patch failed at 0003 cpuidle/ppc: Split timer_interrupt() into timer handling and interrupt handling routines
The copy of the patch that failed is found in:
   /home/paul/git/linux-head/.git/rebase-apply/patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".
$ dry-run
patching file arch/powerpc/kernel/time.c
Hunk #3 FAILED at 544.
Hunk #4 FAILED at 554.
Hunk #5 succeeded at 862 (offset 12 lines).
2 out of 5 hunks FAILED -- saving rejects to file arch/powerpc/kernel/time.c.rej
--------

It appears to conflict with:

commit 0215f7d8c53fb192cd4491ede0ece5cca6b5db57
Author: Benjamin Herrenschmidt [off-list ref]
Date:   Tue Jan 14 17:11:39 2014 +1100

    powerpc: Fix races with irq_work

Thanks for the build test.I will base it on the mainline at the latest
commit as well as on Ben's tree and send out this patchset.

Regards
Preeti U Murthy

Paul.
--

quoted

cpuidle driver for powernv posted by Deepthi Dharwar:
https://lkml.org/lkml/2014/1/14/172

Changes in V5:
-------------
The primary change in this version is in Patch[6/8].
As per the discussions in V4 posting of this patchset, it was decided to
refine handling the wakeup of CPUs in fast-sleep by doing the following:

1. In V4, a polling mechanism was used by the CPU handling broadcast to
find out the time of next wakeup of the CPUs in deep idle states. V5 avoids
polling by a way described under PATCH[6/8] in this patchset.

2. The mechanism of broadcast handling of CPUs in deep idle in the absence of an
external wakeup device should be generic and not arch specific code. Hence in this
version this functionality has been integrated into the tick broadcast framework in
the kernel unlike before where it was handled in powerpc specific code.

3. It was suggested that the "broadcast cpu" can be the time keeping cpu
itself. However this has challenges of its own:

a. The time keeping cpu need not exist when all cpus are idle. Hence there
are phases in time when time keeping cpu is absent. But for the use case that
this patchset is trying to address we rely on the presence of a broadcast cpu
all the time.

b. The nomination and un-assignment of the time keeping cpu is not protected
by a lock today and need not be as well since such is its use case in the
kernel. However we would need locks if we double up the time keeping cpu as the
broadcast cpu.

Hence the broadcast cpu is independent of the time-keeping cpu. However PATCH[6/8]
proposes a simpler solution to pick a broadcast cpu in this version.

Changes in V4:
-------------
https://lkml.org/lkml/2013/11/29/97

1. Add Fast Sleep CPU idle state on PowerNV.

2. Add the required context management for Fast Sleep and the call to OPAL
to synchronize time base after wakeup from fast sleep.

4. Add parsing of CPU idle states from the device tree to populate the
cpuidle
state table.

5. Rename ambiguous functions in the code around waking up of CPUs from fast
sleep.

6. Fixed a bug in re-programming of the hrtimer that is queued to wakeup the
CPUs in fast sleep and modified Changelogs.

7. Added the ARCH_HAS_TICK_BROADCAST option. This signifies that we have a
arch specific function to perform broadcast.

Changes in V3:
-------------
http://thread.gmane.org/gmane.linux.power-management.general/38113

1. Fix the way in which a broadcast ipi is handled on the idling cpus. Timer
handling on a broadcast ipi is being done now without missing out any timer
stats generation.

2. Fix a bug in the programming of the hrtimer meant to do broadcast. Program
it to trigger at the earlier of a "broadcast period", and the next wakeup
event. By introducing the "broadcast period" as the maximum period after
which the broadcast hrtimer can fire, we ensure that we do not miss
wakeups in corner cases.

3. On hotplug of a broadcast cpu, trigger the hrtimer meant to do broadcast
to fire immediately on the new broadcast cpu. This will ensure we do not miss
doing a broadcast pending in the nearest future.

4. Change the type of allocation from GFP_KERNEL to GFP_NOWAIT while
initializing bc_hrtimer since we are in an atomic context and cannot sleep.

5. Use the broadcast ipi to wakeup the newly nominated broadcast cpu on
hotplug of the old instead of smp_call_function_single(). This is because we
are interrupt disabled at this point and should not be using
smp_call_function_single or its children in this context to send an ipi.

6. Move GENERIC_CLOCKEVENTS_BROADCAST to arch/powerpc/Kconfig.

7. Fix coding style issues.

Changes in V2:
-------------
https://lkml.org/lkml/2013/8/14/239

1. Dynamically pick a broadcast CPU, instead of having a dedicated one.
2. Remove the constraint of having to disable tickless idle on the broadcast
CPU by queueing a hrtimer dedicated to do broadcast.

V1 posting: https://lkml.org/lkml/2013/7/25/740.

1. Added the infrastructure to wakeup CPUs in deep idle states in which the
local timers stop.
---

Preeti U Murthy (4):
cpuidle/ppc: Split timer_interrupt() into timer handling and interrupt handling routines
time/cpuidle: Support in tick broadcast framework in the absence of external clock device
cpuidle/powernv: Add "Fast-Sleep" CPU idle state
cpuidle/powernv: Parse device tree to setup idle states

Srivatsa S. Bhat (2):
powerpc: Free up the slot of PPC_MSG_CALL_FUNC_SINGLE IPI message
powerpc: Implement tick broadcast IPI as a fixed IPI message

Vaidyanathan Srinivasan (2):
powernv/cpuidle: Add context management for Fast Sleep
powermgt: Add OPAL call to resync timebase on wakeup

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