[PATCH 2/3] ARM: OMAP4: cpuidle: Use coupled cpuidle states to implement SMP cpuidle.
Shilimkar, Santosh
santosh.shilimkar at ti.com
Sat Mar 31 02:37:14 EDT 2012
On Sat, Mar 31, 2012 at 1:13 AM, Colin Cross <ccross at android.com> wrote:
> On Fri, Mar 30, 2012 at 6:27 AM, Santosh Shilimkar
> <santosh.shilimkar at ti.com> wrote:
>> OMAP4 CPUDILE driver is converted mainly based on notes from the
>> coupled cpuidle patch series.
>>
>> The changes include :
>> - Register both CPUs and C-states to cpuidle driver.
>> - Set struct cpuidle_device.coupled_cpus
>> - Set struct cpuidle_device.safe_state to non coupled state.
>> - Set CPUIDLE_FLAG_COUPLED in struct cpuidle_state.flags for each
>> state that affects multiple cpus.
>> - Separate ->enter hooks for coupled & simple idle.
>> - CPU0 wait loop for CPU1 power transition.
>> - CPU1 wakeup mechanism for the idle exit.
>> - Enabling ARCH_NEEDS_CPU_IDLE_COUPLED for OMAP4.
>>
>> Thanks to Kevin Hilman and Colin Cross on the suggestions/fixes
>> on the intermediate version of this patch.
>>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
>> CC: Kevin Hilman <khilman at ti.com>
>> Cc: Colin Cross <ccross at android.com>
>> ---
>> arch/arm/mach-omap2/Kconfig | 1 +
>> arch/arm/mach-omap2/cpuidle44xx.c | 167 ++++++++++++++++++++++---------------
>> 2 files changed, 101 insertions(+), 67 deletions(-)
>>
>> diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
>> index e20c8ab..250786e 100644
>> --- a/arch/arm/mach-omap2/Kconfig
>> +++ b/arch/arm/mach-omap2/Kconfig
>> @@ -54,6 +54,7 @@ config ARCH_OMAP4
>> select PM_OPP if PM
>> select USB_ARCH_HAS_EHCI
>> select ARM_CPU_SUSPEND if PM
>> + select ARCH_NEEDS_CPU_IDLE_COUPLED if CPU_IDLE
> The "if CPU_IDLE" is not necessary, ARCH_NEEDS_CPU_IDLE_COUPLED is
> designed to have no effect if CPU_IDLE is not set.
>
OK. Will drop that if then.
>>
>> comment "OMAP Core Type"
>> depends on ARCH_OMAP2
>> diff --git a/arch/arm/mach-omap2/cpuidle44xx.c b/arch/arm/mach-omap2/cpuidle44xx.c
>> index f386cbe..5724393 100644
>> --- a/arch/arm/mach-omap2/cpuidle44xx.c
>> +++ b/arch/arm/mach-omap2/cpuidle44xx.c
>> @@ -21,6 +21,7 @@
>> #include "common.h"
>> #include "pm.h"
>> #include "prm.h"
>> +#include "clockdomain.h"
>>
>> #ifdef CONFIG_CPU_IDLE
>>
>> @@ -44,10 +45,11 @@ static struct cpuidle_params cpuidle_params_table[] = {
>> #define OMAP4_NUM_STATES ARRAY_SIZE(cpuidle_params_table)
>>
>> struct omap4_idle_statedata omap4_idle_data[OMAP4_NUM_STATES];
>> -static struct powerdomain *mpu_pd, *cpu0_pd, *cpu1_pd;
>> +static struct powerdomain *mpu_pd, *cpu_pd[NR_CPUS];
>> +static struct clockdomain *cpu_clkdm[NR_CPUS];
>>
>> /**
>> - * omap4_enter_idle - Programs OMAP4 to enter the specified state
>> + * omap4_enter_idle_coupled_[simple/coupled] - OMAP4 cpuidle entry functions
>> * @dev: cpuidle device
>> * @drv: cpuidle driver
>> * @index: the index of state to be entered
>> @@ -56,34 +58,40 @@ static struct powerdomain *mpu_pd, *cpu0_pd, *cpu1_pd;
>> * specified low power state selected by the governor.
>> * Returns the amount of time spent in the low power state.
>> */
>> -static int omap4_enter_idle(struct cpuidle_device *dev,
>> +static int omap4_enter_idle_simple(struct cpuidle_device *dev,
>> + struct cpuidle_driver *drv,
>> + int index)
>> +{
>> + local_fiq_disable();
>> + omap_do_wfi();
>> + local_fiq_enable();
>> +
>> + return index;
>> +}
>> +
>> +static int omap4_enter_idle_coupled(struct cpuidle_device *dev,
>> struct cpuidle_driver *drv,
>> int index)
>> {
>> struct omap4_idle_statedata *cx =
>> cpuidle_get_statedata(&dev->states_usage[index]);
>> - u32 cpu1_state;
>> int cpu_id = smp_processor_id();
>>
>> local_fiq_disable();
>>
>> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu_id);
>> +
>> /*
>> - * CPU0 has to stay ON (i.e in C1) until CPU1 is OFF state.
>> + * CPU0 has to wait and stay ON until CPU1 is OFF state.
>> * This is necessary to honour hardware recommondation
>> * of triggeing all the possible low power modes once CPU1 is
>> * out of coherency and in OFF mode.
>> - * Update dev->last_state so that governor stats reflects right
>> - * data.
>> */
>> - cpu1_state = pwrdm_read_pwrst(cpu1_pd);
>> - if (cpu1_state != PWRDM_POWER_OFF) {
>> - index = drv->safe_state_index;
>> - cx = cpuidle_get_statedata(&dev->states_usage[index]);
>> + if (dev->cpu == 0) {
>> + while (pwrdm_read_pwrst(cpu_pd[1]) != PWRDM_POWER_OFF)
>> + cpu_relax();
> If something goes wrong in the core coupled code or in the cpu 1 power
> state transition, this will hang forever and be hard to debug. It
> might be worth adding a timeout with a BUG_ON.
>
This condition is handled in patch 3/3
>> }
>>
>> - if (index > 0)
>> - clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu_id);
>> -
>> /*
>> * Call idle CPU PM enter notifier chain so that
>> * VFP and per CPU interrupt context is saved.
>> @@ -91,25 +99,35 @@ static int omap4_enter_idle(struct cpuidle_device *dev,
>> if (cx->cpu_state == PWRDM_POWER_OFF)
>> cpu_pm_enter();
> This should never get called without cpu_state == PWRDM_POWER_OFF, and
> even if it did, calling cpu_pm_enter shouldn't hurt anything. It
> would be clearer to unconditionally call cpu_pm_enter().
>
Actually coupled state is called only for CPU mode, so the check can be removed.
>>
>> - pwrdm_set_logic_retst(mpu_pd, cx->mpu_logic_state);
>> - omap_set_pwrdm_state(mpu_pd, cx->mpu_state);
>> -
>> - /*
>> - * Call idle CPU cluster PM enter notifier chain
>> - * to save GIC and wakeupgen context.
>> - */
>> - if ((cx->mpu_state == PWRDM_POWER_RET) &&
>> - (cx->mpu_logic_state == PWRDM_POWER_OFF))
>> - cpu_cluster_pm_enter();
>> + if (dev->cpu == 0) {
>> + pwrdm_set_logic_retst(mpu_pd, cx->mpu_logic_state);
>> + omap_set_pwrdm_state(mpu_pd, cx->mpu_state);
>> +
>> + /*
>> + * Call idle CPU cluster PM enter notifier chain
>> + * to save GIC and wakeupgen context.
>> + */
>> + if ((cx->mpu_state == PWRDM_POWER_RET) &&
>> + (cx->mpu_logic_state == PWRDM_POWER_OFF))
>> + cpu_cluster_pm_enter();
>> + }
>>
>> omap4_enter_lowpower(dev->cpu, cx->cpu_state);
>>
>> + if (dev->cpu == 0) {
>> + /* Wakeup CPU1 only if it is not offlined */
>> + if (cpumask_test_cpu(1, cpu_online_mask)) {
>> + clkdm_wakeup(cpu_clkdm[1]);
>> + clkdm_allow_idle(cpu_clkdm[1]);
>> + }
>> + }
>> +
>> /*
>> * Call idle CPU PM exit notifier chain to restore
>> * VFP and per CPU IRQ context. Only CPU0 state is
>> * considered since CPU1 is managed by CPU hotplug.
>> */
> This comment is no longer accurate? cpu_pm_enter is called on cpu 1 above.
>
Yep. Didn't pay much attention on the comments. Will fix it.
>> - if (pwrdm_read_prev_pwrst(cpu0_pd) == PWRDM_POWER_OFF)
>> + if (pwrdm_read_prev_pwrst(cpu_pd[dev->cpu]) == PWRDM_POWER_OFF)
>> cpu_pm_exit();
> This should get called unconditionally. It's not explicitly stated,
> but the cpu_pm_* api expects cpu_pm_exit() to be called after
> cpu_pm_enter(), even if the low power state was not entered.
> Otherwise, a cpu_pm_enter notifier that disables the hardware will not
> get a chance to re-enable it.
I know what you mean now. the hardware like CPU interface can be
disabled/enabled in the notifiers so would make sense to call them
unconditionally. Will remove the check in both cases.
Regards
Santosh
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