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.
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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