Re: [v7 PATCH 7/7]: pSeries: implement pSeries processor idle module.

[Arun R Bharadwaj <arun@linux.vnet.ibm.com>]

* Arun R Bharadwaj <arun@linux.vnet.ibm.com> [2009-10-06 21:05:22]:

> * Arun R Bharadwaj <arun@linux.vnet.ibm.com> [2009-10-06 20:54:21]:

Please consider this updated PATCH 7/7 instead of the earlier one.
The earlier one had a late_initcall(pseries_processor_idle_init),
which caused a panic when cpuidle_enable_device() was called from
cpuidle_switch_governor(). This is because registration of cpuidle
devices was happening at a later stage. So change this to a
device_initcall() to get rid of the panic.

---

This patch creates arch/powerpc/platforms/pseries/processor_idle.c,
which implements the cpuidle infrastructure for pseries.
It implements a pseries_cpuidle_loop() which would be the main idle loop
called from cpu_idle(). It makes decision of entering either
dedicated_snooze_loop or dedicated_cede_loop for dedicated lpar and
shared_cede_loop for shared lpar processor based on the
decision taken by the cpuidle governor.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/system.h               |    1 
 arch/powerpc/kernel/sysfs.c                     |    2 
 arch/powerpc/platforms/pseries/Makefile         |    1 
 arch/powerpc/platforms/pseries/processor_idle.c |  208 ++++++++++++++++++++++++
 arch/powerpc/platforms/pseries/pseries.h        |    8 
 5 files changed, 220 insertions(+)

Index: linux.trees.git/arch/powerpc/platforms/pseries/Makefile
===================================================================
--- linux.trees.git.orig/arch/powerpc/platforms/pseries/Makefile
+++ linux.trees.git/arch/powerpc/platforms/pseries/Makefile
@@ -26,3 +26,4 @@ obj-$(CONFIG_HCALL_STATS)	+= hvCall_inst
 obj-$(CONFIG_PHYP_DUMP)	+= phyp_dump.o
 obj-$(CONFIG_CMM)		+= cmm.o
 obj-$(CONFIG_DTL)		+= dtl.o
+obj-$(CONFIG_PSERIES_PROCESSOR_IDLE)	+= processor_idle.o
Index: linux.trees.git/arch/powerpc/platforms/pseries/pseries.h
===================================================================
--- linux.trees.git.orig/arch/powerpc/platforms/pseries/pseries.h
+++ linux.trees.git/arch/powerpc/platforms/pseries/pseries.h
@@ -10,6 +10,8 @@
 #ifndef _PSERIES_PSERIES_H
 #define _PSERIES_PSERIES_H
 
+#include <linux/cpuidle.h>
+
 extern void __init fw_feature_init(const char *hypertas, unsigned long len);
 
 struct pt_regs;
@@ -40,4 +42,10 @@ extern unsigned long rtas_poweron_auto;
 
 extern void find_udbg_vterm(void);
 
+DECLARE_PER_CPU(unsigned long, smt_snooze_delay);
+
+#ifdef CONFIG_PSERIES_PROCESSOR_IDLE
+extern struct cpuidle_driver pseries_idle_driver;
+#endif
+
 #endif /* _PSERIES_PSERIES_H */
Index: linux.trees.git/arch/powerpc/platforms/pseries/processor_idle.c
===================================================================
--- /dev/null
+++ linux.trees.git/arch/powerpc/platforms/pseries/processor_idle.c
@@ -0,0 +1,208 @@
+/*
+ *  processor_idle - idle state cpuidle driver.
+ *  Adapted from drivers/acpi/processor_idle.c
+ *
+ *  Arun R Bharadwaj <arun@linux.vnet.ibm.com>
+ *
+ *  Copyright (C) 2009 IBM Corporation.
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or (at
+ *  your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/moduleparam.h>
+#include <linux/cpuidle.h>
+
+#include <asm/paca.h>
+#include <asm/reg.h>
+#include <asm/system.h>
+#include <asm/machdep.h>
+#include <asm/firmware.h>
+
+#include "plpar_wrappers.h"
+#include "pseries.h"
+
+MODULE_AUTHOR("Arun R Bharadwaj");
+MODULE_DESCRIPTION("pSeries Idle State Driver");
+MODULE_LICENSE("GPL");
+
+struct cpuidle_driver pseries_idle_driver = {
+	.name =		"pseries_idle",
+	.owner =	THIS_MODULE,
+};
+
+DEFINE_PER_CPU(struct cpuidle_device, pseries_dev);
+
+#define IDLE_STATE_COUNT	2
+
+/* pSeries Idle state Flags */
+#define	PSERIES_DEDICATED_SNOOZE	(0x01)
+#define	PSERIES_DEDICATED_CEDE		(0x02)
+#define	PSERIES_SHARED_CEDE		(0x03)
+
+static int pseries_idle_init(struct cpuidle_device *dev)
+{
+	return cpuidle_register_device(dev);
+}
+
+static void shared_cede_loop(void)
+{
+	get_lppaca()->idle = 1;
+	cede_processor();
+	get_lppaca()->idle = 0;
+}
+
+static void dedicated_snooze_loop(void)
+{
+	local_irq_enable();
+	set_thread_flag(TIF_POLLING_NRFLAG);
+	while (!need_resched()) {
+		ppc64_runlatch_off();
+		HMT_low();
+		HMT_very_low();
+	}
+	HMT_medium();
+	clear_thread_flag(TIF_POLLING_NRFLAG);
+	smp_mb();
+	local_irq_disable();
+}
+
+static void dedicated_cede_loop(void)
+{
+	ppc64_runlatch_off();
+	HMT_medium();
+	cede_processor();
+}
+
+static int pseries_cpuidle_loop(struct cpuidle_device *dev,
+				struct cpuidle_state *st)
+{
+	ktime_t t1, t2;
+	s64 diff;
+	int ret;
+	unsigned long in_purr, out_purr;
+
+	get_lppaca()->idle = 1;
+	get_lppaca()->donate_dedicated_cpu = 1;
+	in_purr = mfspr(SPRN_PURR);
+
+	t1 = ktime_get();
+
+	if (st->flags & PSERIES_SHARED_CEDE)
+		shared_cede_loop();
+	else if (st->flags & PSERIES_DEDICATED_SNOOZE)
+		dedicated_snooze_loop();
+	else
+		dedicated_cede_loop();
+
+	t2 = ktime_get();
+	diff = ktime_to_us(ktime_sub(t2, t1));
+	if (diff > INT_MAX)
+		diff = INT_MAX;
+
+	ret = (int) diff;
+
+	out_purr = mfspr(SPRN_PURR);
+	get_lppaca()->wait_state_cycles += out_purr - in_purr;
+	get_lppaca()->donate_dedicated_cpu = 0;
+	get_lppaca()->idle = 0;
+
+	return ret;
+}
+
+static int pseries_setup_cpuidle(struct cpuidle_device *dev, int cpu)
+{
+	int i;
+	struct cpuidle_state *state;
+
+	dev->cpu = cpu;
+
+	if (get_lppaca()->shared_proc) {
+		state = &dev->states[0];
+		snprintf(state->name, CPUIDLE_NAME_LEN, "IDLE");
+		state->enter = pseries_cpuidle_loop;
+		strncpy(state->desc, "shared_cede", CPUIDLE_DESC_LEN);
+		state->flags = PSERIES_SHARED_CEDE;
+		state->exit_latency = 0;
+		state->target_residency = 0;
+		return 0;
+	}
+
+	for (i = 0; i < IDLE_STATE_COUNT; i++) {
+		state = &dev->states[i];
+
+		snprintf(state->name, CPUIDLE_NAME_LEN, "CEDE%d", i);
+		state->enter = pseries_cpuidle_loop;
+
+		switch (i) {
+		case 0:
+			strncpy(state->desc, "snooze", CPUIDLE_DESC_LEN);
+			state->flags = PSERIES_DEDICATED_SNOOZE;
+			state->exit_latency = 0;
+			state->target_residency = 0;
+			break;
+
+		case 1:
+			strncpy(state->desc, "cede", CPUIDLE_DESC_LEN);
+			state->flags = PSERIES_DEDICATED_CEDE;
+			state->exit_latency = 1;
+			state->target_residency =
+					__get_cpu_var(smt_snooze_delay);
+			break;
+		}
+	}
+	dev->state_count = IDLE_STATE_COUNT;
+
+	return 0;
+}
+
+void update_smt_snooze_delay(int snooze)
+{
+	int cpu;
+	for_each_online_cpu(cpu)
+		per_cpu(pseries_dev, cpu).states[0].target_residency = snooze;
+}
+
+static int __init pseries_processor_idle_init(void)
+{
+	int cpu;
+	int result = cpuidle_register_driver(&pseries_idle_driver);
+
+	if (result < 0)
+		return result;
+
+	printk(KERN_DEBUG "pSeries idle driver registered\n");
+
+	if (!firmware_has_feature(FW_FEATURE_SPLPAR)) {
+		printk(KERN_DEBUG "Using default idle\n");
+		return 0;
+	}
+
+	for_each_online_cpu(cpu) {
+		pseries_setup_cpuidle(&per_cpu(pseries_dev, cpu), cpu);
+		pseries_idle_init(&per_cpu(pseries_dev, cpu));
+	}
+
+	printk(KERN_DEBUG "Using cpuidle idle loop\n");
+
+	return 0;
+}
+
+device_initcall(pseries_processor_idle_init);
Index: linux.trees.git/arch/powerpc/include/asm/system.h
===================================================================
--- linux.trees.git.orig/arch/powerpc/include/asm/system.h
+++ linux.trees.git/arch/powerpc/include/asm/system.h
@@ -548,6 +548,7 @@ extern void account_system_vtime(struct 
 extern struct dentry *powerpc_debugfs_root;
 
 void cpu_idle_wait(void);
+extern void update_smt_snooze_delay(int snooze);
 
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_SYSTEM_H */
Index: linux.trees.git/arch/powerpc/kernel/sysfs.c
===================================================================
--- linux.trees.git.orig/arch/powerpc/kernel/sysfs.c
+++ linux.trees.git/arch/powerpc/kernel/sysfs.c
@@ -18,6 +18,7 @@
 #include <asm/machdep.h>
 #include <asm/smp.h>
 #include <asm/pmc.h>
+#include <asm/system.h>
 
 #include "cacheinfo.h"
 
@@ -51,6 +52,7 @@ static ssize_t store_smt_snooze_delay(st
 		return -EINVAL;
 
 	per_cpu(smt_snooze_delay, cpu->sysdev.id) = snooze;
+	update_smt_snooze_delay(snooze);
 
 	return count;
 }