Hi,
On 11.11.2013 11:58, Tarek Dakhran wrote:
On Thu, Nov 07, 2013 at 11:51:49AM -0500, Nicolas Pitre wrote:
Samsung people: could you give us more info on the behavior of the power
controller please?
Nicolas
This is how the power controller works on exynos5410. For example for
CORE0.
ARM_CORE0_STATUS register indicates the power state of Core 0 part of
processor core.
0x3 indicates that power to Core 0 is turned-on. 0x0 indicates that
power to Core 0 is turned-off.
All other values indicate that the power On/Off sequence of Core 0 in
progress.
To turn Off the power of Core 0 power domain:
1. Set the LOCAL_POWER_CFG field of ARM_CORE0_CONFIGURATION register
to 0x3.
2. After PMU detects a change in the LOCAL_POWER_CFG field, it waits
for the execution of WFI.
3. After Core 0 executes the WFI instruction, PMU starts the
power-down sequence.
4. The Status field of ARM_CORE0_STATUS register indicates the
completion of the sequence.
That's why in the v1 of this patch exynos_core_power_control function
was implemented as:
static int exynos_core_power_control(unsigned int cpu, unsigned int
cluster, int enable)
{
unsigned long timeout = jiffies + msecs_to_jiffies(10);
unsigned int offset = cluster * MAX_CPUS_PER_CLUSTER + cpu;
int value = enable ? S5P_CORE_LOCAL_PWR_EN : 0;
if ((__raw_readl(EXYNOS5410_CORE_STATUS(offset)) & 0x3) == value)
return 0;
__raw_writel(value, EXYNOS5410_CORE_CONFIGURATION(offset));
do {
if ((__raw_readl(EXYNOS5410_CORE_STATUS(offset)) & 0x3)
== value)
return 0;
} while (time_before(jiffies, timeout));
return -EDEADLK;
}
But, as i mentioned, this is no good using while here.
Now thinking about the problem.
Thank you,
Tarek Dakhran
What do you think about this way of solving the problem with races?
Add new edcs_power_controller_wait function.
static void edcs_power_controller_wait(unsigned int cpu, unsigned int
cluster){
unsigned long timeout = jiffies + msecs_to_jiffies(10);
unsigned int offset = cluster * EDCS_CPUS_PER_CLUSTER + cpu;
void __iomem *status_reg = EDCS_CORE_STATUS(offset);
/* wait till core power controller finish the work */
do {
if ((readl_relaxed(status_reg) & 3) ==
edcs_use_count[cpu][cluster] ? 3 : 0)
return;
} while (time_before(jiffies, timeout));
/* Should never get here */
BUG();
}
Use it in:
static void exynos_core_power_up(unsigned int cpu, unsigned int cluster)
{
exynos_core_power_control(cpu, cluster, true);
edcs_power_controller_wait(cpu, cluster);
}
and in:
static void exynos_power_down(void)
{
bool last_man = false, skip_wfi = false;
unsigned int mpidr = read_cpuid_mpidr();
unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
pr_debug("%s: CORE%d on CLUSTER %d\n", __func__, cpu, cluster);
BUG_ON(cpu >= EDCS_CPUS_PER_CLUSTER || cluster >= EDCS_CLUSTERS);
__mcpm_cpu_going_down(cpu, cluster);
arch_spin_lock(&edcs_lock);
BUG_ON(__mcpm_cluster_state(cluster) != CLUSTER_UP);
edcs_use_count[cpu][cluster]--;
if (edcs_use_count[cpu][cluster] == 0) {
exynos_core_power_down(cpu, cluster);
--core_count[cluster];
if (core_count[cluster] == 0)
last_man = true;
[snip]
__mcpm_cpu_down(cpu, cluster);
if (!skip_wfi){
wfi();
}
edcs_power_controller_wait(cpu, cluster);
}
Comments appreciated. Thanks.
Best regards,
Tarek Dakhran.
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