Subject: Re: [v10 PATCH 8/9]: pSeries: implement pSeries processor idle module

From: Benjamin Herrenschmidt <[email-masked]>
Date: Fri, 04 Dec 2009 13:47:38 +1100

On Wed, 2009-12-02 at 15:32 +0530, Arun R Bharadwaj wrote:
> * Arun R Bharadwaj <[email-masked]> [2009-12-02 15:24:27]:
> 
> 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.

So unless I'm mistaken, you removed our powerpc "generic" idle loop that
calls into ppc_md.power_save(), and replaced it by some pseries specific
idle loops... Now what about all the other powerpc platforms ? native
970 (aka G5) ? 6xx ? Cell ? Or are you still calling ppc_md.power_save
somewhere that I missed ?

Cheers,
Ben.

> Signed-off-by: Arun R Bharadwaj <[email-masked]>
> ---
>  arch/powerpc/include/asm/system.h               |    6 
>  arch/powerpc/kernel/sysfs.c                     |    2 
>  arch/powerpc/platforms/pseries/Makefile         |    1 
>  arch/powerpc/platforms/pseries/processor_idle.c |  196 ++++++++++++++++++++++++
>  arch/powerpc/platforms/pseries/pseries.h        |    6 
>  5 files changed, 211 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_CPU_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 +42,8 @@ extern unsigned long rtas_poweron_auto;
>  
>  extern void find_udbg_vterm(void);
>  
> +DECLARE_PER_CPU(unsigned long, smt_snooze_delay);
> +
> +extern struct cpuidle_driver pseries_idle_driver;
> +
>  #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 +1,196 @@
> +/*
> + *  processor_idle - idle state cpuidle driver.
> + *  Adapted from drivers/acpi/processor_idle.c
> + *
> + *  Arun R Bharadwaj <[email-masked]>
> + *
> + *  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 void pseries_cpuidle_loop(struct cpuidle_device *dev,
> +				struct cpuidle_state *st)
> +{
> +	unsigned long in_purr, out_purr;
> +
> +	get_lppaca()->idle = 1;
> +	get_lppaca()->donate_dedicated_cpu = 1;
> +	in_purr = mfspr(SPRN_PURR);
> +
> +	if (st->flags & PSERIES_SHARED_CEDE)
> +		shared_cede_loop();
> +	else if (st->flags & PSERIES_DEDICATED_SNOOZE)
> +		dedicated_snooze_loop();
> +	else
> +		dedicated_cede_loop();
> +
> +	out_purr = mfspr(SPRN_PURR);
> +	get_lppaca()->wait_state_cycles += out_purr - in_purr;
> +	get_lppaca()->donate_dedicated_cpu = 0;
> +	get_lppaca()->idle = 0;
> +}
> +
> +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;
> +
> +	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
> @@ -549,5 +549,11 @@ extern struct dentry *powerpc_debugfs_ro
>  
>  void cpu_idle_wait(void);
>  
> +#ifdef CONFIG_CPU_IDLE
> +extern void update_smt_snooze_delay(int snooze);
> +#else
> +static inline void update_smt_snooze_delay(int snooze) {}
> +#endif
> +
>  #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;
>  }