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ARM: vexpress/dcscb: add CPU use counts to the power up/down API implementation

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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 to deal
with this possibility as mandated by the MCPM 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>
This commit is contained in:
Nicolas Pitre 2012-07-16 22:07:10 -04:00
parent 1e904e1bf6
commit 13eae144ec
1 changed files with 59 additions and 15 deletions
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74
arch/arm/mach-vexpress/dcscb.c
View file

@ -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.
@ -122,7 +150,8 @@ static void dcscb_power_down(void)
/* Now we are prepared for power-down, do it: */
dsb();
wfi();
if (!skip_wfi)
wfi();
/* Not dead at this point? Let our caller cope. */
}
@ -132,6 +161,19 @@ 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 +186,8 @@ 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);