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Message-ID: <20140528043856.15676.35844.stgit@preeti.in.ibm.com>
Date: Wed, 28 May 2014 10:08:56 +0530
From: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To: benh@...nel.crashing.org, linux-kernel@...r.kernel.org,
svaidyan@...ibm.com, paulus@...ba.org,
srivatsa.bhat@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 2/6] powerpc, powernv,
CPU hotplug: Put offline CPUs in Fast-Sleep instead of Nap
From: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
The offline cpus are put to fast sleep if the idle state is discovered in the
device tree. This is to gain maximum powersavings in the offline state.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
[ Changelog added by <preeti@...ux.vnet.ibm.com> ]
Signed-off-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
---
arch/powerpc/include/asm/processor.h | 8 +++++
arch/powerpc/kernel/idle.c | 52 ++++++++++++++++++++++++++++++++++
arch/powerpc/platforms/powernv/smp.c | 12 +++++++-
3 files changed, 71 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index d922e5c..c5256db 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -449,6 +449,14 @@ static inline unsigned long get_clean_sp(unsigned long sp, int is_32)
#define IDLE_INST_NAP 0x00010000 /* nap instruction can be used */
#define IDLE_INST_SLEEP 0x00020000 /* sleep instruction can be used */
+/* Flags to indicate which of the CPU idle states are available for use */
+
+#define IDLE_USE_NAP (1UL << 0)
+#define IDLE_USE_SLEEP (1UL << 1)
+
+extern unsigned int supported_cpuidle_states;
+extern unsigned int pnv_get_supported_cpuidle_states(void);
+
extern unsigned long cpuidle_disable;
enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};
diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c
index d7216c9..e51d574 100644
--- a/arch/powerpc/kernel/idle.c
+++ b/arch/powerpc/kernel/idle.c
@@ -25,6 +25,7 @@
#include <linux/cpu.h>
#include <linux/sysctl.h>
#include <linux/tick.h>
+#include <linux/of.h>
#include <asm/processor.h>
#include <asm/cputable.h>
@@ -32,6 +33,7 @@
#include <asm/machdep.h>
#include <asm/runlatch.h>
#include <asm/smp.h>
+#include <asm/firmware.h>
unsigned long cpuidle_disable = IDLE_NO_OVERRIDE;
@@ -79,6 +81,56 @@ void arch_cpu_idle(void)
ppc64_runlatch_on();
}
+#ifdef CONFIG_PPC_POWERNV
+
+unsigned int supported_cpuidle_states = 0;
+
+unsigned int pnv_get_supported_cpuidle_states(void)
+{
+ return supported_cpuidle_states;
+}
+
+static int __init pnv_probe_idle_states(void)
+{
+ struct device_node *power_mgt;
+ struct property *prop;
+ int dt_idle_states;
+ u32 *flags;
+ int i;
+
+ if (!firmware_has_feature(FW_FEATURE_OPALv3))
+ return 0;
+
+ power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
+ if (!power_mgt) {
+ pr_warn("opal: PowerMgmt Node not found\n");
+ return 0;
+ }
+
+ prop = of_find_property(power_mgt, "ibm,cpu-idle-state-flags", NULL);
+ if (!prop) {
+ pr_warn("DT-PowerMgmt: missing ibm,cpu-idle-state-flags\n");
+ return 0;
+ }
+
+ dt_idle_states = prop->length / sizeof(u32);
+ flags = (u32 *) prop->value;
+
+ for (i = 0; i < dt_idle_states; i++) {
+ if (flags[i] & IDLE_INST_NAP)
+ supported_cpuidle_states |= IDLE_USE_NAP;
+
+ if (flags[i] & IDLE_INST_SLEEP)
+ supported_cpuidle_states |= IDLE_USE_SLEEP;
+ }
+
+ return 0;
+}
+
+__initcall(pnv_probe_idle_states);
+#endif
+
+
int powersave_nap;
#ifdef CONFIG_SYSCTL
diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index bf5fcd4..fc83006 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -31,6 +31,7 @@
#include <asm/xics.h>
#include <asm/opal.h>
#include <asm/runlatch.h>
+#include <asm/processor.h>
#include "powernv.h"
@@ -142,6 +143,7 @@ static int pnv_smp_cpu_disable(void)
static void pnv_smp_cpu_kill_self(void)
{
unsigned int cpu;
+ unsigned long idle_states;
/* Standard hot unplug procedure */
local_irq_disable();
@@ -152,13 +154,21 @@ static void pnv_smp_cpu_kill_self(void)
generic_set_cpu_dead(cpu);
smp_wmb();
+ idle_states = pnv_get_supported_cpuidle_states();
+
/* We don't want to take decrementer interrupts while we are offline,
* so clear LPCR:PECE1. We keep PECE2 enabled.
*/
mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1);
while (!generic_check_cpu_restart(cpu)) {
ppc64_runlatch_off();
- power7_nap();
+
+ /* If sleep is supported, go to sleep, instead of nap */
+ if (idle_states & IDLE_USE_SLEEP)
+ power7_sleep();
+ else
+ power7_nap();
+
ppc64_runlatch_on();
if (!generic_check_cpu_restart(cpu)) {
DBG("CPU%d Unexpected exit while offline !\n", cpu);
--
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