Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964890AbbDOGY3 (ORCPT ); Wed, 15 Apr 2015 02:24:29 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:39459 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964835AbbDOGYV (ORCPT ); Wed, 15 Apr 2015 02:24:21 -0400 From: "Shreyas B. Prabhu" To: linux-kernel@vger.kernel.org Cc: ego@linux.vnet.ibm.com, preeti@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au, benh@kernel.crashing.org, "Shreyas B. Prabhu" Subject: [PATCH v5 0/3] powerpc: powernv: Fastsleep workaround behavior Date: Wed, 15 Apr 2015 11:54:06 +0530 Message-Id: <1429079049-5955-1-git-send-email-shreyas@linux.vnet.ibm.com> X-Mailer: git-send-email 1.9.3 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15041506-0005-0000-0000-00000A188A80 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2726 Lines: 68 Fastsleep is one of the idle state which cpuidle subsystem currently uses on power8 machines. In this state L2 cache is brought down to a threshold voltage. Therefore when the core is in fastsleep, the communication between L2 and L3 needs to be fenced. But there is a bug in the current power8 chips surrounding this fencing. OPAL provides a workaround which precludes the possibility of hitting this bug. But running with this workaround applied causes checkstop if any correctable error in L2 cache directory is detected. Hence OPAL also provides a way to undo the workaround. In the existing implementation, workaround is applied by the last thread of the core entering fastsleep and undone by the first thread waking up. But this has a performance cost. These OPAL calls account for roughly 4000 cycles everytime the core has to enter or wakeup from fastsleep. This patchset introduces a sysfs attribute (fastsleep_workaround_state) to choose the behavior of this workaround. Patch 1/3 fixes cpu_online_cores_map which is used by Patch 3/3. Patch 2/3 is a clean up patch. It moves all cpuidle related code into a new file. Patch 3/3 introduces the sysfs attribute to control fastsleep workaround behavior Changes in v5: - Fix potential race with hotplug with get_online_cpu/put_online_cpu Changes in v4: ------------- -Handling patch_instruction and OPAL call errors -Sysfs attribute takes string ("dynamic" vs "applyonce") as input. -Improved changelogs Changes in v3: -------------- -Kernel parameter changed to sysfs attribute Changes in v2: -------------- -Changed commit message to accurately describe the downside of running workaround always applied. Shreyas B. Prabhu (3): powerpc: Fix cpu_online_cores_map to return only online threads mask powerpc/powernv: Move cpuidle related code from setup.c to new file powerpc/powernv: Introduce sysfs control for fastsleep workaround behavior arch/powerpc/include/asm/cputhreads.h | 13 +- arch/powerpc/include/asm/opal-api.h | 7 + arch/powerpc/include/asm/opal.h | 1 + arch/powerpc/platforms/powernv/Makefile | 2 +- arch/powerpc/platforms/powernv/idle.c | 323 +++++++++++++++++++++++++ arch/powerpc/platforms/powernv/opal-wrappers.S | 1 + arch/powerpc/platforms/powernv/setup.c | 171 ------------- 7 files changed, 341 insertions(+), 177 deletions(-) create mode 100644 arch/powerpc/platforms/powernv/idle.c -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/