From patchwork Thu Jan 10 00:20:46 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 1957991 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 33E433FC5A for ; Thu, 10 Jan 2013 00:29:12 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1Tt5x0-0001yg-OY; Thu, 10 Jan 2013 00:24:55 +0000 Received: from relais.videotron.ca ([24.201.245.36]) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1Tt5tW-0008T3-Ib for linux-arm-kernel@lists.infradead.org; Thu, 10 Jan 2013 00:21:20 +0000 Received: from yoda.home ([24.202.213.203]) by VL-VM-MR003.ip.videotron.ca (Oracle Communications Messaging Exchange Server 7u4-22.01 64bit (built Apr 21 2011)) with ESMTP id <0MGD00D15VMYNP31@VL-VM-MR003.ip.videotron.ca> for linux-arm-kernel@lists.infradead.org; Wed, 09 Jan 2013 19:20:59 -0500 (EST) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 266452DA01CB for ; Wed, 09 Jan 2013 19:20:59 -0500 (EST) From: Nicolas Pitre To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 11/16] ARM: vexpress/dcscb: add CPU use counts to the power up/down API implementation Date: Wed, 09 Jan 2013 19:20:46 -0500 Message-id: <1357777251-13541-12-git-send-email-nicolas.pitre@linaro.org> X-Mailer: git-send-email 1.8.0 In-reply-to: <1357777251-13541-1-git-send-email-nicolas.pitre@linaro.org> References: <1357777251-13541-1-git-send-email-nicolas.pitre@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130109_192119_080764_8890408B X-CRM114-Status: GOOD ( 16.75 ) 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 It is possible for a CPU to be told to power up before it managed to power itself down. Solve this race with a usage count as mandated by the API definition. Signed-off-by: nicolas Pitre --- arch/arm/mach-vexpress/dcscb.c | 74 +++++++++++++++++++++++++++++++++--------- 1 file changed, 59 insertions(+), 15 deletions(-) diff --git a/arch/arm/mach-vexpress/dcscb.c b/arch/arm/mach-vexpress/dcscb.c index cccd943cd4..81dd443b95 100644 --- a/arch/arm/mach-vexpress/dcscb.c +++ b/arch/arm/mach-vexpress/dcscb.c @@ -43,6 +43,7 @@ static arch_spinlock_t dcscb_lock = __ARCH_SPIN_LOCK_UNLOCKED; static void __iomem *dcscb_base; +static int dcscb_use_count[4][2]; static int dcscb_power_up(unsigned int cpu, unsigned int cluster) { @@ -59,14 +60,27 @@ static int dcscb_power_up(unsigned int cpu, unsigned int cluster) local_irq_disable(); arch_spin_lock(&dcscb_lock); - rst_hold = readl_relaxed(dcscb_base + RST_HOLD0 + cluster * 4); - if (rst_hold & (1 << 8)) { - /* remove cluster reset and add individual CPU's reset */ - rst_hold &= ~(1 << 8); - rst_hold |= 0xf; + dcscb_use_count[cpu][cluster]++; + if (dcscb_use_count[cpu][cluster] == 1) { + rst_hold = readl_relaxed(dcscb_base + RST_HOLD0 + cluster * 4); + if (rst_hold & (1 << 8)) { + /* remove cluster reset and add individual CPU's reset */ + rst_hold &= ~(1 << 8); + rst_hold |= 0xf; + } + rst_hold &= ~(cpumask | (cpumask << 4)); + writel(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4); + } else if (dcscb_use_count[cpu][cluster] != 2) { + /* + * The only possible values are: + * 0 = CPU down + * 1 = CPU (still) up + * 2 = CPU requested to be up before it had a chance + * to actually make itself down. + * Any other value is a bug. + */ + BUG(); } - rst_hold &= ~(cpumask | (cpumask << 4)); - writel(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4); arch_spin_unlock(&dcscb_lock); local_irq_enable(); @@ -76,7 +90,8 @@ static int dcscb_power_up(unsigned int cpu, unsigned int cluster) static void dcscb_power_down(void) { - unsigned int mpidr, cpu, cluster, rst_hold, cpumask, last_man; + unsigned int mpidr, cpu, cluster, rst_hold, cpumask; + bool last_man = false, skip_wfi = false; asm ("mrc p15, 0, %0, c0, c0, 5" : "=r" (mpidr)); cpu = mpidr & 0xff; @@ -87,13 +102,26 @@ static void dcscb_power_down(void) BUG_ON(cpu >= 4 || cluster >= 2); arch_spin_lock(&dcscb_lock); - rst_hold = readl_relaxed(dcscb_base + RST_HOLD0 + cluster * 4); - rst_hold |= cpumask; - if (((rst_hold | (rst_hold >> 4)) & 0xf) == 0xf) - rst_hold |= (1 << 8); - writel(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4); + dcscb_use_count[cpu][cluster]--; + if (dcscb_use_count[cpu][cluster] == 0) { + rst_hold = readl_relaxed(dcscb_base + RST_HOLD0 + cluster * 4); + rst_hold |= cpumask; + if (((rst_hold | (rst_hold >> 4)) & 0xf) == 0xf) { + rst_hold |= (1 << 8); + last_man = true; + } + writel(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4); + } else if (dcscb_use_count[cpu][cluster] == 1) { + /* + * A power_up request went ahead of us. + * Even if we do not want to shut this CPU down, + * the caller expects a certain state as if the WFI + * was aborted. So let's continue with cache cleaning. + */ + skip_wfi = true; + } else + BUG(); arch_spin_unlock(&dcscb_lock); - last_man = (rst_hold & (1 << 8)); /* * Now let's clean our L1 cache and shut ourself down. @@ -124,7 +152,8 @@ static void dcscb_power_down(void) : : : "ip" ); /* Now we are prepared for power-down, do it: */ - wfi(); + if (!skip_wfi) + wfi(); /* Not dead at this point? Let our caller cope. */ } @@ -134,6 +163,19 @@ static const struct bL_platform_power_ops dcscb_power_ops = { .power_down = dcscb_power_down, }; +static void __init dcscb_usage_count_init(void) +{ + unsigned int mpidr, cpu, cluster; + + asm ("mrc p15, 0, %0, c0, c0, 5" : "=r" (mpidr)); + cpu = mpidr & 0xff; + cluster = (mpidr >> 8) & 0xff; + + pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster); + BUG_ON(cpu >= 4 || cluster >= 2); + dcscb_use_count[cpu][cluster] = 1; +} + static int __init dcscb_init(void) { int ret; @@ -142,6 +184,8 @@ static int __init dcscb_init(void) if (!dcscb_base) return -ENOMEM; + dcscb_usage_count_init(); + ret = bL_platform_power_register(&dcscb_power_ops); if (ret) { iounmap(dcscb_base);