[v2] cpufreq/arm-bl-cpufreq: Add simple cpufreq big.LITTLE switcher frontend

Message ID	1332258545-20223-1-git-send-email-dave.martin@linaro.org
State	Not Applicable
Headers	show Return-Path: <patch+caf_=linaro-patchwork=canonical.com@linaro.org> Received-SPF: neutral (google.com: 209.85.214.50 is neither permitted nor denied by best guess record for domain of dave.martin@linaro.org) client-ip=209.85.214.50; From: Dave Martin <dave.martin@linaro.org> To: linaro-big-little@lists.linaro.org Cc: patches@linaro.org, Chris Redpath <Chris.Redpath@arm.com>, Morten Rasmussen <Morten.Rasmussen@arm.com>, Robin Randhawa <Robin.Randhawa@arm.com>, Dave Martin <dave.martin@linaro.org> Subject: [PATCH v2] cpufreq/arm-bl-cpufreq: Add simple cpufreq big.LITTLE switcher frontend Date: Tue, 20 Mar 2012 15:49:05 +0000 Message-Id: <1332258545-20223-1-git-send-email-dave.martin@linaro.org>

diff --git a/Documentation/cpu-freq/cpufreq-arm-bl.txt b/Documentation/cpu-freq/cpufreq-arm-bl.txt new file mode 100644 index 0000000..52e2f3a --- /dev/null +++ b/Documentation/cpu-freq/cpufreq-arm-bl.txt @@ -0,0 +1,47 @@ +Synchronous cluster switching interface for the ARM big.LITTLE switcher +----------------------------------------------------------------------- + +The arm-bl-cpufreq driver provides a simple interface which models two +clusters as two performance points. + +Within each CPU's cpufreq directory in sysfs +(/sys/devices/system/cpu/cpu?/cpufreq/): + +cpuinfo_max_freq: + + reports the dummy frequency value which corresponds to the "big" + cluster. + +cpuinfo_min_freq: + + reports the dummy frequency value which corresponds to the + "little" cluster. + +cpuinfo_cur_freq: + + reports the dummy frequency corresponding to the currently + running cluster. + + +To switch clusters, either the built-in "powersave" or "performance" +governors can be used to force the "little" or "big" cluster +respectively; or alternatively the "userspace" governor can be used, + +The following script fragment demonstrates how the userspace governor +can be used to switch: + + +for x in /sys/devices/system/cpu/cpu[0-9]*; do + echo userspace >$x/cpufreq/scaling_governor +done + +big_freq=`cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq` +little_freq=`cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq` + +switch_to_big () { + echo $big_freq >/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed +} + +switch_to_little () { + echo $little_freq >/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed +} diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 455367d..907d44a 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -301,6 +301,7 @@ config ARCH_VERSATILE config ARCH_VEXPRESS bool "ARM Ltd. Versatile Express family" select ARCH_WANT_OPTIONAL_GPIOLIB + select ARCH_HAS_CPUFREQ select ARM_AMBA select ARM_TIMER_SP804 select CLKDEV_LOOKUP diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm index 72a0044..0e4f6d0 100644 --- a/drivers/cpufreq/Kconfig.arm +++ b/drivers/cpufreq/Kconfig.arm @@ -30,3 +30,21 @@ config ARM_EXYNOS4210_CPUFREQ SoC (S5PV310 or S5PC210). If in doubt, say N. + +config ARM_BL_CPUFREQ + depends on EXPERIMENTAL + depends on ARCH_VEXPRESS_DT + tristate "Simple cpufreq interface for the ARM big.LITTLE switcher" + help + Provides a simple cpufreq interface to control the ARM + big.LITTLE switcher. + + Note that this code is not currently safe unless the + big.LITTLE switcher binary has been loaded separately by an + external bootloader or firmware before entering the kernel. + Otherwise, you can still build this code as a module, + providing that you don't load it. + + Refer to Documentation/cpufreq/cpufreq-arm-bl.txt for details. + + If unsure, say N. diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile index a48bc02..ecf492d 100644 --- a/drivers/cpufreq/Makefile +++ b/drivers/cpufreq/Makefile @@ -40,6 +40,10 @@ obj-$(CONFIG_X86_CPUFREQ_NFORCE2) += cpufreq-nforce2.o ################################################################################## # ARM SoC drivers obj-$(CONFIG_UX500_SOC_DB8500) += db8500-cpufreq.o +obj-$(CONFIG_ARM_BL_CPUFREQ) += arm-bl-cpufreq.o +arm-bl-cpufreq-y += arm-bl-cpufreq_driver.o \ + arm-bl-cpufreq_hvc.o +AFLAGS_arm-bl-cpufreq_hvc.o := -march=armv7-a obj-$(CONFIG_ARM_S3C64XX_CPUFREQ) += s3c64xx-cpufreq.o obj-$(CONFIG_ARM_S5PV210_CPUFREQ) += s5pv210-cpufreq.o obj-$(CONFIG_ARM_EXYNOS4210_CPUFREQ) += exynos4210-cpufreq.o diff --git a/drivers/cpufreq/arm-bl-cpufreq.h b/drivers/cpufreq/arm-bl-cpufreq.h new file mode 100644 index 0000000..2f9b0dc --- /dev/null +++ b/drivers/cpufreq/arm-bl-cpufreq.h @@ -0,0 +1,13 @@ +#ifndef ARM_BL_CPUFREQ_HVC_H +#define ARM_BL_CPUFREQ_HVC_H + +#ifndef __ASSEMBLY__ +int __arm_bl_get_cluster(void); +void __arm_bl_switch_cluster(void); +#endif /* ! __ASSEMBLY__ */ + +/* Hypervisor call numbers for the ARM big.LITTLE switcher: */ +#define ARM_BL_HVC_SWITCH_CLUSTER 1 +#define ARM_BL_HVC_GET_MPIDR 2 + +#endif /* ! ARM_BL_CPUFREQ_HVC_H */ diff --git a/drivers/cpufreq/arm-bl-cpufreq_driver.c b/drivers/cpufreq/arm-bl-cpufreq_driver.c new file mode 100644 index 0000000..faf2fc0 --- /dev/null +++ b/drivers/cpufreq/arm-bl-cpufreq_driver.c @@ -0,0 +1,217 @@ +/* + * arm-bl-cpufreq.c: Simple cpufreq backend for the ARM big.LITTLE switcher + * Copyright (C) 2012 Linaro Limited + * + * 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., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +/* WARNING: This code is experimental and depends on external firmware */ + +#include <linux/bug.h> +#include <linux/cache.h> +#include <linux/cpufreq.h> +#include <linux/cpumask.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/printk.h> +#include <linux/string.h> +#include <linux/spinlock.h> + +#include "arm-bl-cpufreq.h" + +#define DRIVER_NAME "arm-bl" +#define MODULE_NAME "arm-bl-cpufreq" + +#define info(format...) printk(KERN_INFO MODULE_NAME ": " format) +#define warn(format...) printk(KERN_WARNING MODULE_NAME ": " format) + +/* Dummy frequencies representing the big and little clusters: */ +#define FREQ_BIG 1000000 +#define FREQ_LITTLE 100000 + +/* Cluster numbers */ +#define CLUSTER_BIG 0 +#define CLUSTER_LITTLE 1 + +static DEFINE_SPINLOCK(switcher_lock); + +static struct cpufreq_frequency_table __read_mostly bl_freqs[] = { + { CLUSTER_BIG, FREQ_BIG }, + { CLUSTER_LITTLE, FREQ_LITTLE }, + { 0, CPUFREQ_TABLE_END }, +}; + + +/* Miscellaneous helpers */ + +static unsigned int cluster_to_freq(int cluster) +{ + unsigned int i; + + for(i = 0; bl_freqs[i].frequency != CPUFREQ_TABLE_END; i++) + if(bl_freqs[i].index == cluster) + return bl_freqs[i].frequency; + + WARN(1, "%s: %s(): invalid cluster number %d, assuming 0\n", + MODULE_NAME, __func__, cluster); + return bl_freqs[0].frequency; +} + +/* + * Functions to get the current status. + * + * If you intend to use the result (i.e., it's not just for diagnostic + * purposes) then you should be holding switcher_lock ... otherwise + * the current cluster may change unexpectedly. + */ +static int get_current_cluster(void) +{ + return (__arm_bl_get_cluster() >> 8) & 0xF; +} + +static unsigned int get_current_freq(void) +{ + return cluster_to_freq(get_current_cluster()); +} + +/* + * Switch to the requested cluster. + * There is no "switch_to_frequency" function, because the cpufreq frequency + * table helpers can easily look up the appropriate cluster number for us. + */ +static void switch_to_cluster(int cluster) +{ + info("Switching to cluster %d\n", cluster); + + spin_lock(&switcher_lock); + if(cluster != get_current_cluster()) + __arm_bl_switch_cluster(); + spin_unlock(&switcher_lock); +} + + +/* Cpufreq methods and module code */ + +static int bl_cpufreq_init(struct cpufreq_policy *policy) +{ + int err; + + /* + * Set CPU and policy min and max frequencies based on bl_freqs: + */ + err = cpufreq_frequency_table_cpuinfo(policy, bl_freqs); + if (err) + goto error; + + /* + * No need for locking here: + * cpufreq is not active until initialisation has finished. + * Ideally, transition_latency should be calibrated here. + */ + policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL; + policy->cur = get_current_freq(); + + /* + * A b.L switch can be triggered from any CPU, but will affect them all. + * The set of related CPUs should perhaps be determined from the + * system CPU topology, rather than just the set of CPUs present... + */ + policy->shared_type = CPUFREQ_SHARED_TYPE_ANY; + cpumask_copy(policy->related_cpus, cpu_present_mask); + /* + * We do not set ->cpus here, because it doesn't actually matter if + * we try to switch on two CPUs at the same time. Setting ->cpus + * to cpu_present_mask might provide a way to avoid the need to take + * switcher_lock when switching, though. + */ + + info("cpufreq initialised successfully\n"); + return 0; + +error: + warn("%s: cpufreq initialisation failed (%d)\n", __func__, err); + return err; +} + +static int bl_cpufreq_verify(struct cpufreq_policy *policy) +{ + return cpufreq_frequency_table_verify(policy, bl_freqs); +} + +static int bl_cpufreq_target(struct cpufreq_policy *policy, + unsigned int target_freq, + unsigned int relation) +{ + int err; + int index; + + if(cpufreq_frequency_table_target(policy, bl_freqs, target_freq, + relation, &index)) + return err; + + switch_to_cluster(bl_freqs[index].index); + return 0; +} + +static unsigned int bl_cpufreq_get(unsigned int __always_unused cpu) +{ + /* + * The cpu argument is ignored, because all CPUs have the same + * performance point, by definition. + */ + return get_current_freq(); +} + +static struct cpufreq_driver __read_mostly bl_cpufreq_driver = { + .owner = THIS_MODULE, + .name = DRIVER_NAME, + + .init = bl_cpufreq_init, + .verify = bl_cpufreq_verify, + .target = bl_cpufreq_target, + .get = bl_cpufreq_get, + /* what else? */ +}; + +static int __init bl_cpufreq_module_init(void) +{ + int err; + + err = cpufreq_register_driver(&bl_cpufreq_driver); + if(err) + info("cpufreq backend driver registration failed (%d)\n", err); + else + info("cpufreq backend driver registered.\n"); + + return err; +} +module_init(bl_cpufreq_module_init); + +static void __exit bl_cpufreq_module_exit(void) +{ + cpufreq_unregister_driver(&bl_cpufreq_driver); + + /* Restore the "default" cluster: */ + switch_to_cluster(CLUSTER_BIG); + + info("cpufreq backend driver unloaded.\n"); +} +module_exit(bl_cpufreq_module_exit); + + +MODULE_AUTHOR("Dave Martin"); +MODULE_DESCRIPTION("Simple cpufreq interface for the ARM big.LITTLE switcher"); +MODULE_LICENSE("GPL"); diff --git a/drivers/cpufreq/arm-bl-cpufreq_hvc.S b/drivers/cpufreq/arm-bl-cpufreq_hvc.S new file mode 100644 index 0000000..6c7eb6d --- /dev/null +++ b/drivers/cpufreq/arm-bl-cpufreq_hvc.S @@ -0,0 +1,15 @@ +#include <linux/linkage.h> + +#include "arm-bl-cpufreq.h" + +.arch_extension virt + +ENTRY(__arm_bl_get_cluster) + hvc #ARM_BL_HVC_GET_MPIDR + bx lr +ENDPROC(__arm_bl_get_cluster) + +ENTRY(__arm_bl_switch_cluster) + hvc #ARM_BL_HVC_SWITCH_CLUSTER + bx lr +ENDPROC(__arm_bl_switch_cluster)

[v2] cpufreq/arm-bl-cpufreq: Add simple cpufreq big.LITTLE switcher frontend

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