From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicolas.pitre@linaro.org (Nicolas Pitre) Date: Wed, 09 Jan 2013 19:20:46 -0500 Subject: [PATCH 11/16] ARM: vexpress/dcscb: add CPU use counts to the power up/down API implementation In-Reply-To: <1357777251-13541-1-git-send-email-nicolas.pitre@linaro.org> References: <1357777251-13541-1-git-send-email-nicolas.pitre@linaro.org> Message-ID: <1357777251-13541-12-git-send-email-nicolas.pitre@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.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@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); -- 1.8.0