[PATCH v2 1/3] powerpc/powernv: Enable Offline CPUs to enter deep idle states

[Shreyas B. Prabhu]

From: "Srivatsa S. Bhat" <srivatsa@xxxxxxx>

The offline cpus should enter deep idle states so as to gain maximum
powersavings when the entire core is offline. To do so the offline path
must be made aware of the available deepest idle state. Hence probe the
device tree for the possible idle states in powernv core code and
expose the deepest idle state through flags.

Since the  device tree is probed by the cpuidle driver as well, move
the parameters required to discover the idle states into an appropriate
common place to both the driver and the powernv core code.

Another point is that fastsleep idle state may require workarounds in
the kernel to function properly. This workaround is introduced in the
subsequent patches. However neither the cpuidle driver or the hotplug
path need be bothered about this workaround.

They will be taken care of by the core powernv code.

Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Signed-off-by: Srivatsa S. Bhat <srivatsa@xxxxxxx>
Signed-off-by: Shreyas B. Prabhu <shreyas@xxxxxxxxxxxxxxxxxx>
[ Changelog modified by preeti@xxxxxxxxxxxxxxxxxx ]
Signed-off-by: Preeti U. Murthy <preeti@xxxxxxxxxxxxxxxxxx>
---
 arch/powerpc/include/asm/opal.h          |  4 +++
 arch/powerpc/platforms/powernv/powernv.h |  7 +++++
 arch/powerpc/platforms/powernv/setup.c   | 51 ++++++++++++++++++++++++++++++++
 arch/powerpc/platforms/powernv/smp.c     | 11 ++++++-
 drivers/cpuidle/cpuidle-powernv.c        |  7 ++---
 5 files changed, 75 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 86055e5..28b8342 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -772,6 +772,10 @@ extern struct kobject *opal_kobj;
 /* /ibm,opal */
 extern struct device_node *opal_node;
 
+/* Flags used for idle state discovery from the device tree */
+#define IDLE_INST_NAP	0x00010000 /* nap instruction can be used */
+#define IDLE_INST_SLEEP	0x00020000 /* sleep instruction can be used */
+
 /* API functions */
 int64_t opal_invalid_call(void);
 int64_t opal_console_write(int64_t term_number, __be64 *length,
diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
index 75501bf..31ece13 100644
--- a/arch/powerpc/platforms/powernv/powernv.h
+++ b/arch/powerpc/platforms/powernv/powernv.h
@@ -23,6 +23,13 @@ static inline int pnv_pci_dma_set_mask(struct pci_dev *pdev, u64 dma_mask)
 }
 #endif
 
+/* 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 pnv_get_supported_cpuidle_states(void);
+
 extern void pnv_lpc_init(void);
 
 bool cpu_core_split_required(void);
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 5a0e2dc..2dca1d8 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -282,6 +282,57 @@ static void __init pnv_setup_machdep_rtas(void)
 }
 #endif /* CONFIG_PPC_POWERNV_RTAS */
 
+static unsigned int supported_cpuidle_states;
+
+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;
+
+	supported_cpuidle_states = 0;
+
+	if (cpuidle_disable != IDLE_NO_OVERRIDE)
+		return 0;
+
+	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;
+}
+
+subsys_initcall(pnv_probe_idle_states);
+
 static int __init pnv_probe(void)
 {
 	unsigned long root = of_get_flat_dt_root();
diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index 5fcfcf4..3ad31d2 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -149,6 +149,7 @@ 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();
@@ -159,13 +160,21 @@ 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(1);
+
+		/* If sleep is supported, go to sleep, instead of nap */
+		if (idle_states & IDLE_USE_SLEEP)
+			power7_sleep();
+		else
+			power7_nap(1);
+
 		ppc64_runlatch_on();
 
 		/* Reenable IRQs briefly to clear the IPI that woke us */
diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index a64be57..23d2743 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -16,13 +16,12 @@
 
 #include <asm/machdep.h>
 #include <asm/firmware.h>
+#include <asm/opal.h>
 #include <asm/runlatch.h>
 
 /* Flags and constants used in PowerNV platform */
 
 #define MAX_POWERNV_IDLE_STATES	8
-#define IDLE_USE_INST_NAP	0x00010000 /* Use nap instruction */
-#define IDLE_USE_INST_SLEEP	0x00020000 /* Use sleep instruction */
 
 struct cpuidle_driver powernv_idle_driver = {
 	.name             = "powernv_idle",
@@ -185,7 +184,7 @@ static int powernv_add_idle_states(void)
 	for (i = 0; i < dt_idle_states; i++) {
 
 		flags = be32_to_cpu(idle_state_flags[i]);
-		if (flags & IDLE_USE_INST_NAP) {
+		if (flags & IDLE_INST_NAP) {
 			/* Add NAP state */
 			strcpy(powernv_states[nr_idle_states].name, "Nap");
 			strcpy(powernv_states[nr_idle_states].desc, "Nap");
@@ -196,7 +195,7 @@ static int powernv_add_idle_states(void)
 			nr_idle_states++;
 		}
 
-		if (flags & IDLE_USE_INST_SLEEP) {
+		if (flags & IDLE_INST_SLEEP) {
 			/* Add FASTSLEEP state */
 			strcpy(powernv_states[nr_idle_states].name, "FastSleep");
 			strcpy(powernv_states[nr_idle_states].desc, "FastSleep");
-- 
1.9.3

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