On Wed, 2013-08-14 at 17:26 +0530, Preeti U Murthy wrote:
> This patch hooks into the existing broadcast framework along with the support
> that this patchset introduces for ppc, and the cpuidle driver backend
> for powernv(posted out by Deepthi Dharwar:https://lkml.org/lkml/2013/7/23/128)
> to add sleep state as one of the deep idle states, in which the decrementer
> is switched off.
>
> However in this patch, we only emulate sleep by going into a state which does
> a nap with the decrementer interrupts disabled, termed as longnap. This
> enables
> focus on the timer broadcast framework for ppc in this series of patches ,
> which is required as a first step to enable sleep on ppc.
This is only for debug / proof of concept right ? We should use a real
sleep here.
If we need to know whether the FW supports it (PORE etc...) we shall add
a device-tree property from the FW to indicate that fact.
Cheers,
Ben.
> Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com>
> ---
>
> arch/powerpc/platforms/powernv/processor_idle.c | 48
> +++++++++++++++++++++++
> 1 file changed, 47 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/processor_idle.c
> b/arch/powerpc/platforms/powernv/processor_idle.c
> index f43ad91a..9aca502 100644
> --- a/arch/powerpc/platforms/powernv/processor_idle.c
> +++ b/arch/powerpc/platforms/powernv/processor_idle.c
> @@ -9,16 +9,18 @@
> #include <linux/cpuidle.h>
> #include <linux/cpu.h>
> #include <linux/notifier.h>
> +#include <linux/clockchips.h>
>
> #include <asm/machdep.h>
> #include <asm/runlatch.h>
> +#include <asm/time.h>
>
> struct cpuidle_driver powernv_idle_driver = {
> .name = "powernv_idle",
> .owner = THIS_MODULE,
> };
>
> -#define MAX_IDLE_STATE_COUNT 2
> +#define MAX_IDLE_STATE_COUNT 3
>
> static int max_idle_state = MAX_IDLE_STATE_COUNT - 1;
> static struct cpuidle_device __percpu *powernv_cpuidle_devices;
> @@ -54,6 +56,43 @@ static int nap_loop(struct cpuidle_device *dev,
> return index;
> }
>
> +/* Emulate sleep, with long nap.
> + * During sleep, the core does not receive decrementer interrupts.
> + * Emulate sleep using long nap with decrementers interrupts disabled.
> + * This is an initial prototype to test the timer offload framework for ppc.
> + * We will eventually introduce the sleep state once the timer offload
> framework
> + * for ppc is stable.
> + */
> +static int longnap_loop(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int index)
> +{
> + int cpu = dev->cpu;
> +
> + unsigned long lpcr = mfspr(SPRN_LPCR);
> +
> + lpcr &= ~(LPCR_MER | LPCR_PECE); /* lpcr[mer] must be 0 */
> +
> + /* exit powersave upon external interrupt, but not decrementer
> + * interrupt, Emulate sleep.
> + */
> + lpcr |= LPCR_PECE0;
> +
> + if (cpu != bc_cpu) {
> + mtspr(SPRN_LPCR, lpcr);
> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
> + power7_nap();
> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
> + } else {
> + /* Wakeup on a decrementer interrupt, Do a nap */
> + lpcr |= LPCR_PECE1;
> + mtspr(SPRN_LPCR, lpcr);
> + power7_nap();
> + }
> +
> + return index;
> +}
> +
> /*
> * States for dedicated partition case.
> */
> @@ -72,6 +111,13 @@ static struct cpuidle_state
> powernv_states[MAX_IDLE_STATE_COUNT] = {
> .exit_latency = 10,
> .target_residency = 100,
> .enter = &nap_loop },
> + { /* LongNap */
> + .name = "LongNap",
> + .desc = "LongNap",
> + .flags = CPUIDLE_FLAG_TIME_VALID,
> + .exit_latency = 10,
> + .target_residency = 100,
> + .enter = &longnap_loop },
> };
>
> static int powernv_cpuidle_add_cpu_notifier(struct notifier_block *n,
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