On Wednesday, June 24, 2015 01:48:01 AM Preeti U Murthy wrote:
> On some archs, the local clockevent device stops in deep cpuidle states.
> The broadcast framework is used to wakeup cpus in these idle states, in
> which either an external clockevent device is used to send wakeup ipis
> or the hrtimer broadcast framework kicks in in the absence of such a
> device. One cpu is nominated as the broadcast cpu and this cpu sends
> wakeup ipis to sleeping cpus at the appropriate time. This is the
> implementation in the oneshot mode of broadcast.
>
> In periodic mode of broadcast however, the presence of such cpuidle
> states results in the cpuidle driver calling tick_broadcast_enable()
> which shuts down the local clockevent devices of all the cpus and
> appoints the tick broadcast device as the clockevent device for each of
> them. This works on those archs where the tick broadcast device is a
> real clockevent device. But on archs which depend on the hrtimer mode
> of broadcast, the tick broadcast device hapens to be a pseudo device.
> The consequence is that the local clockevent devices of all cpus are
> shutdown and the kernel hangs at boot time in periodic mode.
>
> Let us thus not register the cpuidle states which have
> CPUIDLE_FLAG_TIMER_STOP flag set, on archs which depend on the hrtimer
> mode of broadcast in periodic mode. This patch takes care of doing this
> on powerpc. The cpus would not have entered into such deep cpuidle
> states in periodic mode on powerpc anyway. So there is no loss here.
>
> Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com>
4.2 material I suppose?
> ---
> drivers/cpuidle/cpuidle-powernv.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-powernv.c
> b/drivers/cpuidle/cpuidle-powernv.c
> index 5937207..3442764 100644
> --- a/drivers/cpuidle/cpuidle-powernv.c
> +++ b/drivers/cpuidle/cpuidle-powernv.c
> @@ -60,6 +60,8 @@ static int nap_loop(struct cpuidle_device *dev,
> return index;
> }
>
> +/* Register for fastsleep only in oneshot mode of broadcast */
> +#ifdef CONFIG_TICK_ONESHOT
> static int fastsleep_loop(struct cpuidle_device *dev,
> struct cpuidle_driver *drv,
> int index)
> @@ -83,7 +85,7 @@ static int fastsleep_loop(struct cpuidle_device *dev,
>
> return index;
> }
> -
> +#endif
> /*
> * States for dedicated partition case.
> */
> @@ -209,7 +211,14 @@ static int powernv_add_idle_states(void)
> powernv_states[nr_idle_states].flags = 0;
> powernv_states[nr_idle_states].target_residency = 100;
> powernv_states[nr_idle_states].enter = &nap_loop;
> - } else if (flags[i] & OPAL_PM_SLEEP_ENABLED ||
> + }
> +
> + /*
> + * All cpuidle states with CPUIDLE_FLAG_TIMER_STOP set must come
> + * within this config dependency check.
> + */
> +#ifdef CONFIG_TICK_ONESHOT
> + if (flags[i] & OPAL_PM_SLEEP_ENABLED ||
> flags[i] & OPAL_PM_SLEEP_ENABLED_ER1) {
> /* Add FASTSLEEP state */
> strcpy(powernv_states[nr_idle_states].name,
> "FastSleep");
> @@ -218,7 +227,7 @@ static int powernv_add_idle_states(void)
> powernv_states[nr_idle_states].target_residency =
> 300000;
> powernv_states[nr_idle_states].enter = &fastsleep_loop;
> }
> -
> +#endif
> powernv_states[nr_idle_states].exit_latency =
> ((unsigned int)latency_ns[i]) / 1000;
>
>
> --
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--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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