From patchwork Thu Jan 24 06:27:49 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 2029201 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by patchwork1.kernel.org (Postfix) with ESMTP id 9D03F3FD56 for ; Thu, 24 Jan 2013 06:31:52 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1TyGJP-0004Hr-Dk; Thu, 24 Jan 2013 06:29:23 +0000 Received: from relais.videotron.ca ([24.201.245.36]) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1TyGID-0003pw-SW for linux-arm-kernel@lists.infradead.org; Thu, 24 Jan 2013 06:28:14 +0000 Received: from yoda.home ([24.202.213.203]) by VL-VM-MR002.ip.videotron.ca (Oracle Communications Messaging Exchange Server 7u4-22.01 64bit (built Apr 21 2011)) with ESMTP id <0MH400JZS9YSTA80@VL-VM-MR002.ip.videotron.ca> for linux-arm-kernel@lists.infradead.org; Thu, 24 Jan 2013 01:28:04 -0500 (EST) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 641632DA044F for ; Thu, 24 Jan 2013 01:28:04 -0500 (EST) From: Nicolas Pitre To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 06/16] ARM: bL_head.S: vlock-based first man election Date: Thu, 24 Jan 2013 01:27:49 -0500 Message-id: <1359008879-9015-7-git-send-email-nicolas.pitre@linaro.org> X-Mailer: git-send-email 1.8.0 In-reply-to: <1359008879-9015-1-git-send-email-nicolas.pitre@linaro.org> References: <1359008879-9015-1-git-send-email-nicolas.pitre@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130124_012810_032173_C9567314 X-CRM114-Status: GOOD ( 14.36 ) X-Spam-Score: -1.9 (-) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-1.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [24.201.245.36 listed in list.dnswl.org] -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: Dave Martin Instead of requiring the first man to be elected in advance (which can be suboptimal in some situations), this patch uses a per- cluster mutex to co-ordinate selection of the first man. This should also make it more feasible to reuse this code path for asynchronous cluster resume (as in CPUidle scenarios). We must ensure that the vlock data doesn't share a cacheline with anything else, or dirty cache eviction could corrupt it. Signed-off-by: Dave Martin Signed-off-by: Nicolas Pitre --- arch/arm/common/Makefile | 2 +- arch/arm/common/bL_head.S | 41 ++++++++++++++++++++++++++++++++++++----- 2 files changed, 37 insertions(+), 6 deletions(-) diff --git a/arch/arm/common/Makefile b/arch/arm/common/Makefile index 8025899a20..aa797237a7 100644 --- a/arch/arm/common/Makefile +++ b/arch/arm/common/Makefile @@ -13,4 +13,4 @@ obj-$(CONFIG_SHARP_PARAM) += sharpsl_param.o obj-$(CONFIG_SHARP_SCOOP) += scoop.o obj-$(CONFIG_PCI_HOST_ITE8152) += it8152.o obj-$(CONFIG_ARM_TIMER_SP804) += timer-sp.o -obj-$(CONFIG_BIG_LITTLE) += bL_head.o bL_entry.o +obj-$(CONFIG_BIG_LITTLE) += bL_head.o bL_entry.o vlock.o diff --git a/arch/arm/common/bL_head.S b/arch/arm/common/bL_head.S index a226cdf4ce..86bcc8a003 100644 --- a/arch/arm/common/bL_head.S +++ b/arch/arm/common/bL_head.S @@ -16,6 +16,8 @@ #include #include +#include "vlock.h" + .if BL_SYNC_CLUSTER_CPUS .error "cpus must be the first member of struct bL_cluster_sync_struct" .endif @@ -64,10 +66,11 @@ ENTRY(bL_entry_point) * position independent way. */ adr r5, 3f - ldmia r5, {r6, r7, r8} + ldmia r5, {r6, r7, r8, r11} add r6, r5, r6 @ r6 = bL_entry_vectors ldr r7, [r5, r7] @ r7 = bL_power_up_setup_phys add r8, r5, r8 @ r8 = bL_sync + add r11, r5, r11 @ r11 = first_man_locks mov r0, #BL_SYNC_CLUSTER_SIZE mla r8, r0, r10, r8 @ r8 = bL_sync cluster base @@ -81,13 +84,22 @@ ENTRY(bL_entry_point) @ At this point, the cluster cannot unexpectedly enter the GOING_DOWN @ state, because there is at least one active CPU (this CPU). - @ Note: the following is racy as another CPU might be testing - @ the same flag at the same moment. That'll be fixed later. + mov r0, #VLOCK_SIZE + mla r11, r0, r10, r11 @ r11 = cluster first man lock + mov r0, r11 + mov r1, r9 @ cpu + bl vlock_trylock @ implies DMB + + cmp r0, #0 @ failed to get the lock? + bne cluster_setup_wait @ wait for cluster setup if so + ldrb r0, [r8, #BL_SYNC_CLUSTER_CLUSTER] cmp r0, #CLUSTER_UP @ cluster already up? bne cluster_setup @ if not, set up the cluster - @ Otherwise, skip setup: + @ Otherwise, release the first man lock and skip setup: + mov r0, r11 + bl vlock_unlock b cluster_setup_complete cluster_setup: @@ -137,6 +149,19 @@ cluster_setup_leave: dsb sev + mov r0, r11 + bl vlock_unlock @ implies DMB + b cluster_setup_complete + + @ In the contended case, non-first men wait here for cluster setup + @ to complete: +cluster_setup_wait: + ldrb r0, [r8, #BL_SYNC_CLUSTER_CLUSTER] + cmp r0, #CLUSTER_UP + wfene + bne cluster_setup_wait + dmb + cluster_setup_complete: @ If a platform-specific CPU setup hook is needed, it is @ called from here. @@ -168,11 +193,17 @@ bL_entry_gated: 3: .word bL_entry_vectors - . .word bL_power_up_setup_phys - 3b .word bL_sync - 3b + .word first_man_locks - 3b ENDPROC(bL_entry_point) .bss - .align 5 + + .align __CACHE_WRITEBACK_ORDER + .type first_man_locks, #object +first_man_locks: + .space VLOCK_SIZE * BL_MAX_CLUSTERS + .align __CACHE_WRITEBACK_ORDER .type bL_entry_vectors, #object ENTRY(bL_entry_vectors)