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authorNicolas Pitre <nicolas.pitre@linaro.org>2012-07-16 22:07:10 -0400
committerJon Medhurst <tixy@linaro.org>2013-05-03 12:11:40 +0100
commit0f80732f5d51be9c981a78cbcbecdc5b72f7a1e6 (patch)
tree54e071aa421478f2eda19e70a3e1fa9863eacac7
parent22744ffd55b1d0794c265679769d2308c0cb5360 (diff)
downloadvexpress-lsk-0f80732f5d51be9c981a78cbcbecdc5b72f7a1e6.tar.gz
ARM: vexpress/dcscb: add CPU use counts to the power up/down API implementation
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 <nico@linaro.org> Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Acked-by: Pawel Moll <pawel.moll@arm.com>
-rw-r--r--arch/arm/mach-vexpress/dcscb.c77
1 files changed, 61 insertions, 16 deletions
diff --git a/arch/arm/mach-vexpress/dcscb.c b/arch/arm/mach-vexpress/dcscb.c
index ad44881adae..946b332ab99 100644
--- a/arch/arm/mach-vexpress/dcscb.c
+++ b/arch/arm/mach-vexpress/dcscb.c
@@ -44,6 +44,7 @@
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)
{
@@ -60,14 +61,27 @@ 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_relaxed(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_relaxed(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4);
arch_spin_unlock(&dcscb_lock);
local_irq_enable();
@@ -77,7 +91,8 @@ 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;
mpidr = read_cpuid_mpidr();
cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
@@ -88,13 +103,26 @@ 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_relaxed(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_relaxed(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.
@@ -121,8 +149,10 @@ static void dcscb_power_down(void)
set_auxcr(get_auxcr() & ~(1 << 6));
/* Now we are prepared for power-down, do it: */
- dsb();
- wfi();
+ if (!skip_wfi) {
+ dsb();
+ wfi();
+ }
/* Not dead at this point? Let our caller cope. */
}
@@ -132,6 +162,19 @@ static const struct mcpm_platform_ops dcscb_power_ops = {
.power_down = dcscb_power_down,
};
+static void __init dcscb_usage_count_init(void)
+{
+ unsigned int mpidr, cpu, cluster;
+
+ mpidr = read_cpuid_mpidr();
+ cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
+ cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
+
+ 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)
{
struct device_node *node;
@@ -144,6 +187,8 @@ static int __init dcscb_init(void)
if (!dcscb_base)
return -EADDRNOTAVAIL;
+ dcscb_usage_count_init();
+
ret = mcpm_platform_register(&dcscb_power_ops);
if (ret) {
iounmap(dcscb_base);