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    SubjectRe: [RFC PATCH V1 5/7] cpuidle: (POWER) cpuidle driver for pSeries
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    On Tue, 2011-06-07 at 22:00 +0530, Trinabh Gupta wrote:

    > +static int snooze_loop(struct cpuidle_device *dev,
    > + struct cpuidle_driver *drv,
    > + int index)
    > +{
    > + unsigned long in_purr, out_purr;
    > + ktime_t kt_before, kt_after;
    > + s64 usec_delta;
    > +
    > + /*
    > + * Indicate to the HV that we are idle. Now would be
    > + * a good time to find other work to dispatch.
    > + */
    > + get_lppaca()->idle = 1;
    > + get_lppaca()->donate_dedicated_cpu = 1;
    > + in_purr = mfspr(SPRN_PURR);
    > +
    > + kt_before = ktime_get_real();

    Don't you want to timestamp before you tell the HV that you are idle ?
    Or is the above stuff only polled by phyp when partition interrupts are
    enabled ?

    > + local_irq_enable();
    > + set_thread_flag(TIF_POLLING_NRFLAG);
    > + while (!need_resched()) {
    > + ppc64_runlatch_off();
    > + HMT_low();
    > + HMT_very_low();
    > + }
    > + HMT_medium();
    > + clear_thread_flag(TIF_POLLING_NRFLAG);
    > + smp_mb();
    > + local_irq_disable();
    > +
    > + kt_after = ktime_get_real();
    > + usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
    > +
    > + out_purr = mfspr(SPRN_PURR);
    > + get_lppaca()->wait_state_cycles += out_purr - in_purr;
    > + get_lppaca()->donate_dedicated_cpu = 0;
    > + get_lppaca()->idle = 0;
    > +
    > + dev->last_residency = (int)usec_delta;
    > +
    > + return index;
    > +}
    > +
    > +static int dedicated_cede_loop(struct cpuidle_device *dev,
    > + struct cpuidle_driver *drv,
    > + int index)
    > +{
    > + unsigned long in_purr, out_purr;
    > + ktime_t kt_before, kt_after;
    > + s64 usec_delta;
    > +
    > + /*
    > + * Indicate to the HV that we are idle. Now would be
    > + * a good time to find other work to dispatch.
    > + */
    > + get_lppaca()->idle = 1;
    > + get_lppaca()->donate_dedicated_cpu = 1;
    > + in_purr = mfspr(SPRN_PURR);
    > +
    > + kt_before = ktime_get_real();

    There's a bit too much code duplication for my taste here between the
    two functions. Not sure if it can be helped, maybe with some inlines
    for the prolog/epilogue ... Looks like stuff that's easy to "fix" in one
    place and forget the other...

    > + ppc64_runlatch_off();
    > + HMT_medium();
    > + cede_processor();
    > +
    > + kt_after = ktime_get_real();
    > + usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
    > +
    > + out_purr = mfspr(SPRN_PURR);
    > + get_lppaca()->wait_state_cycles += out_purr - in_purr;
    > + get_lppaca()->donate_dedicated_cpu = 0;
    > + get_lppaca()->idle = 0;
    > +
    > + dev->last_residency = (int)usec_delta;
    > +
    > + return index;
    > +}
    > +
    > +static int shared_cede_loop(struct cpuidle_device *dev,
    > + struct cpuidle_driver *drv,
    > + int index)
    > +{
    > + unsigned long in_purr, out_purr;
    > + ktime_t kt_before, kt_after;
    > + s64 usec_delta;
    > +
    > + /*
    > + * Indicate to the HV that we are idle. Now would be
    > + * a good time to find other work to dispatch.
    > + */
    > + get_lppaca()->idle = 1;
    > + get_lppaca()->donate_dedicated_cpu = 1;
    > + in_purr = mfspr(SPRN_PURR);
    > +
    > + kt_before = ktime_get_real();
    > + /*
    > + * Yield the processor to the hypervisor. We return if
    > + * an external interrupt occurs (which are driven prior
    > + * to returning here) or if a prod occurs from another
    > + * processor. When returning here, external interrupts
    > + * are enabled.
    > + */
    > + cede_processor();
    > +
    > + kt_after = ktime_get_real();
    > +
    > + usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
    > +
    > + out_purr = mfspr(SPRN_PURR);
    > + get_lppaca()->wait_state_cycles += out_purr - in_purr;
    > + get_lppaca()->donate_dedicated_cpu = 0;
    > + get_lppaca()->idle = 0;
    > +
    > + dev->last_residency = (int)usec_delta;
    > +
    > + return index;
    > +}
    > +
    > +/*
    > + * States for dedicated partition case.
    > + */
    > +static struct cpuidle_state dedicated_states[MAX_IDLE_STATE_COUNT] = {
    > + { /* Snooze */
    > + .name = "snooze",
    > + .desc = "snooze",
    > + .flags = CPUIDLE_FLAG_TIME_VALID,
    > + .exit_latency = 0,
    > + .target_residency = 0,
    > + .enter = &snooze_loop },
    > + { /* CEDE */
    > + .name = "CEDE",
    > + .desc = "CEDE",
    > + .flags = CPUIDLE_FLAG_TIME_VALID,
    > + .exit_latency = 1,
    > + .target_residency = 10,
    > + .enter = &dedicated_cede_loop },
    > +};
    > +
    > +/*
    > + * States for shared partition case.
    > + */
    > +static struct cpuidle_state shared_states[MAX_IDLE_STATE_COUNT] = {
    > + { /* Shared Cede */
    > + .name = "Shared Cede",
    > + .desc = "Shared Cede",
    > + .flags = CPUIDLE_FLAG_TIME_VALID,
    > + .exit_latency = 0,
    > + .target_residency = 0,
    > + .enter = &shared_cede_loop },
    > +};
    > +
    > +int pseries_notify_cpuidle_add_cpu(int cpu)
    > +{
    > + struct cpuidle_device *dev =
    > + per_cpu_ptr(pseries_idle_cpuidle_devices, cpu);
    > + if (dev && cpuidle_get_driver()) {
    > + cpuidle_disable_device(dev);
    > + cpuidle_enable_device(dev);
    > + }
    > + return 0;
    > +}
    > +
    > +/*
    > + * pseries_idle_cpuidle_driver_init()
    > + */
    > +static int pseries_idle_cpuidle_driver_init(void)
    > +{
    > + int cstate;
    > + struct cpuidle_driver *drv = &pseries_idle_driver;
    > +
    > + drv->state_count = 0;
    > +
    > + for (cstate = 0; cstate < MAX_IDLE_STATE_COUNT; ++cstate) {
    > +
    > + if (cstate > max_cstate)
    > + break;
    > +
    > + /* is the state not enabled? */
    > + if (cpuidle_state_table[cstate].enter == NULL)
    > + continue;
    > +
    > + drv->states[drv->state_count] = /* structure copy */
    > + cpuidle_state_table[cstate];
    > +
    > + if (cpuidle_state_table == dedicated_states)
    > + drv->states[drv->state_count].target_residency =
    > + __get_cpu_var(smt_snooze_delay);
    > +
    > + drv->state_count += 1;
    > + }
    > +
    > + return 0;
    > +}
    > +
    > +/* pseries_idle_devices_uninit(void)
    > + * unregister cpuidle devices and de-allocate memory
    > + */
    > +static void pseries_idle_devices_uninit(void)
    > +{
    > + int i;
    > + struct cpuidle_device *dev;
    > +
    > + for_each_possible_cpu(i) {
    > + dev = per_cpu_ptr(pseries_idle_cpuidle_devices, i);
    > + cpuidle_unregister_device(dev);
    > + }
    > +
    > + free_percpu(pseries_idle_cpuidle_devices);
    > + return;
    > +}
    > +
    > +/* pseries_idle_devices_init()
    > + * allocate, initialize and register cpuidle device
    > + */
    > +static int pseries_idle_devices_init(void)
    > +{
    > + int i;
    > + struct cpuidle_driver *drv = &pseries_idle_driver;
    > + struct cpuidle_device *dev;
    > +
    > + pseries_idle_cpuidle_devices = alloc_percpu(struct cpuidle_device);
    > + if (pseries_idle_cpuidle_devices == NULL)
    > + return -ENOMEM;
    > +
    > + for_each_possible_cpu(i) {
    > + dev = per_cpu_ptr(pseries_idle_cpuidle_devices, i);
    > + dev->state_count = drv->state_count;
    > + dev->cpu = i;
    > + if (cpuidle_register_device(dev)) {
    > + printk(KERN_DEBUG "cpuidle_register_device %d failed!\n",
    > + i);
    > + return -EIO;
    > + }
    > + }
    > +
    > + return 0;
    > +}
    > +
    > +/*
    > + * pseries_idle_probe()
    > + * Choose state table for shared versus dedicated partition
    > + */
    > +static int pseries_idle_probe(void)
    > +{
    > + if (max_cstate == 0) {
    > + printk(KERN_DEBUG "pseries processor idle disabled.\n");
    > + return -EPERM;
    > + }
    > +
    > + if (!firmware_has_feature(FW_FEATURE_SPLPAR)) {
    > + printk(KERN_DEBUG "Using default idle\n");
    > + return -ENODEV;
    > + }
    > +
    > + if (get_lppaca()->shared_proc)
    > + cpuidle_state_table = shared_states;
    > + else
    > + cpuidle_state_table = dedicated_states;
    > +
    > + return 0;
    > +}
    > +
    > +static int __init pseries_processor_idle_init(void)
    > +{
    > + int retval;
    > +
    > + retval = pseries_idle_probe();
    > + if (retval)
    > + return retval;
    > +
    > + pseries_idle_cpuidle_driver_init();
    > + retval = cpuidle_register_driver(&pseries_idle_driver);
    > + if (retval) {
    > + printk(KERN_DEBUG "Registration of pseries driver failed.\n");
    > + return retval;
    > + }
    > +
    > + retval = pseries_idle_devices_init();
    > + if (retval) {
    > + pseries_idle_devices_uninit();
    > + cpuidle_unregister_driver(&pseries_idle_driver);
    > + return retval;
    > + }
    > +
    > + printk(KERN_DEBUG "pseries_idle_driver registered\n");
    > +
    > + return 0;
    > +}
    > +
    > +device_initcall(pseries_processor_idle_init);
    > diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h
    > index e9f6d28..7c60380 100644
    > --- a/arch/powerpc/platforms/pseries/pseries.h
    > +++ b/arch/powerpc/platforms/pseries/pseries.h
    > @@ -56,4 +56,7 @@ extern struct device_node *dlpar_configure_connector(u32);
    > extern int dlpar_attach_node(struct device_node *);
    > extern int dlpar_detach_node(struct device_node *);
    >
    > +/* Snooze Delay, pseries_idle */
    > +DECLARE_PER_CPU(long, smt_snooze_delay);
    > +
    > #endif /* _PSERIES_PSERIES_H */
    > diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
    > index 593acce..6893a0c 100644
    > --- a/arch/powerpc/platforms/pseries/setup.c
    > +++ b/arch/powerpc/platforms/pseries/setup.c
    > @@ -584,9 +584,6 @@ static int __init pSeries_probe(void)
    > return 1;
    > }
    >
    > -
    > -DECLARE_PER_CPU(long, smt_snooze_delay);
    > -
    > static void pseries_dedicated_idle_sleep(void)
    > {
    > unsigned int cpu = smp_processor_id();
    > diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
    > index fbffd7e..2e46883 100644
    > --- a/arch/powerpc/platforms/pseries/smp.c
    > +++ b/arch/powerpc/platforms/pseries/smp.c
    > @@ -150,6 +150,7 @@ static void __devinit smp_xics_setup_cpu(int cpu)
    > set_cpu_current_state(cpu, CPU_STATE_ONLINE);
    > set_default_offline_state(cpu);
    > #endif
    > + pseries_notify_cpuidle_add_cpu(cpu);
    > }
    >
    > static int __devinit smp_pSeries_kick_cpu(int nr)
    >
    > _______________________________________________
    > Linuxppc-dev mailing list
    > Linuxppc-dev@lists.ozlabs.org
    > https://lists.ozlabs.org/listinfo/linuxppc-dev




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