linux-kernel - Re: [PATCH 0/9] powerpc/powernv: Support for fastsleep and winkle

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Message-ID: <128377046.aOTypBOIY8@vostro.rjw.lan>
Date:	Tue, 30 Sep 2014 01:28:50 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Shreyas B Prabhu <shreyas@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org,
	Michael Ellerman <mpe@...erman.id.au>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	"Srivatsa S. Bhat" <srivatsa@....edu>,
	"Preeti U. Murthy" <preeti@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Rob Herring <robh+dt@...nel.org>,
	Grant Likely <grant.likely@...aro.org>,
	devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 0/9] powerpc/powernv: Support for fastsleep and winkle

On Monday, September 29, 2014 03:53:06 PM Shreyas B Prabhu wrote:
> Hi,
> Any updates on this patch series?

I have a couple of patches from there in my tree it seems.  Please have a look
at linux-pm.git/linux-next and please let me know if that's the case.


> On Thursday 18 September 2014 08:41 AM, Shreyas B Prabhu wrote:
> > Hi,
> > 
> > In this patch series we use winkle for offlined cores. I successfully
> > tested the working of this with subcore functionality.
> > 
> > Test scenario was as follows:
> > 1. Set SMT mode to 1, Set subores-per-core to 1
> > 2. Offline a core, in this case cpu 32 (sending it to winkle)
> > 3. Set subcores-per-core to 4
> > 4. Online the core
> > 5. Start a guest (Topology 1 core 2 threads) on a subcore, in this case
> > on cpu 36
> > 
> > This works without any glitch.
> > 
> > Thanks,
> > Shreyas
> > 
> > On Monday 25 August 2014 11:31 PM, Shreyas B. Prabhu wrote:
> >> Fast sleep is an idle state, where the core and the L1 and L2
> >> caches are brought down to a threshold voltage. This also means that
> >> the communication between L2 and L3 caches have to be fenced. However
> >> the current P8 chips have a bug wherein this fencing between L2 and
> >> L3 caches get delayed by a cpu cycle. This can delay L3 response to
> >> the other cpus if they request for data during this time. Thus they
> >> would fetch the same data from the memory which could lead to data
> >> corruption if L3 cache is not flushed.
> >> Patch 4 adds support to work around this.
> >>
> >> 'Deep Winkle' is a deeper idle state where core and private L2 are powered
> >> off. While it offers higher power savings, it is at the cost of losing
> >> hypervisor register state and higher latency.
> >> Patch 5-9 adds support for winkle and uses it for offline cpus.
> >>
> >> Patch 1 - Moves parameters required discover idle states to a location 
> >> common to both cpuidle driver and powernv core code
> >> Patch 2 - Populates idle state details from device tree
> >> Patch 3 - Enables cpus to run guest after waking up from fastsleep/winkle
> >>
> >>
> >> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> >> Cc: Paul Mackerras <paulus@...ba.org>
> >> Cc: Michael Ellerman <mpe@...erman.id.au>
> >> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> >> Cc: Srivatsa S. Bhat <srivatsa@....EDU>
> >> Cc: Preeti U. Murthy <preeti@...ux.vnet.ibm.com>
> >> Cc: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
> >> Cc: Rob Herring <robh+dt@...nel.org>
> >> Cc: Grant Likely <grant.likely@...aro.org>
> >> Cc: devicetree@...r.kernel.org
> >> Cc: linux-pm@...r.kernel.org
> >> Cc: linuxppc-dev@...ts.ozlabs.org
> >>
> >> Preeti U Murthy (2):
> >>   cpuidle/powernv: Populate cpuidle state details by querying the
> >>     device-tree
> >>   powerpc/powernv/cpuidle: Add workaround to enable fastsleep
> >>
> >> Shreyas B. Prabhu (6):
> >>   powerpc/kvm/book3s_hv: Enable CPUs to run guest after waking up from
> >>     fast-sleep
> >>   powerpc/powernv: Add OPAL call to save and restore
> >>   powerpc: Adding macro for accessing Thread Switch Control Register
> >>   powerpc/powernv: Add winkle infrastructure
> >>   powerpc/powernv: Discover and enable winkle
> >>   powerpc/powernv: Enter deepest supported idle state in offline
> >>
> >> Srivatsa S. Bhat (1):
> >>   powerpc/powernv: Enable Offline CPUs to enter deep idle states
> >>
> >>  arch/powerpc/include/asm/machdep.h             |   4 +
> >>  arch/powerpc/include/asm/opal.h                |  10 ++
> >>  arch/powerpc/include/asm/paca.h                |   3 +
> >>  arch/powerpc/include/asm/ppc-opcode.h          |   2 +
> >>  arch/powerpc/include/asm/processor.h           |   6 +-
> >>  arch/powerpc/include/asm/reg.h                 |   1 +
> >>  arch/powerpc/kernel/asm-offsets.c              |   1 +
> >>  arch/powerpc/kernel/exceptions-64s.S           |  37 ++---
> >>  arch/powerpc/kernel/idle.c                     |  30 ++++
> >>  arch/powerpc/kernel/idle_power7.S              |  83 +++++++++-
> >>  arch/powerpc/platforms/powernv/opal-wrappers.S |   2 +
> >>  arch/powerpc/platforms/powernv/powernv.h       |   8 +
> >>  arch/powerpc/platforms/powernv/setup.c         | 217 +++++++++++++++++++++++++
> >>  arch/powerpc/platforms/powernv/smp.c           |  13 +-
> >>  arch/powerpc/platforms/powernv/subcore.c       |  15 ++
> >>  drivers/cpuidle/cpuidle-powernv.c              |  40 ++++-
> >>  16 files changed, 439 insertions(+), 33 deletions(-)
> >>
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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