diff options
Diffstat (limited to 'drivers/cpufreq/arm-bl-cpufreq.c')
| -rw-r--r-- | drivers/cpufreq/arm-bl-cpufreq.c | 244 |
1 files changed, 244 insertions, 0 deletions
diff --git a/drivers/cpufreq/arm-bl-cpufreq.c b/drivers/cpufreq/arm-bl-cpufreq.c new file mode 100644 index 00000000000..e37140f0f1b --- /dev/null +++ b/drivers/cpufreq/arm-bl-cpufreq.c @@ -0,0 +1,244 @@ +/* + * 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. + */ + +#define MODULE_NAME "arm-bl-cpufreq" +#define pr_fmt(fmt) MODULE_NAME ": " fmt + +#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 <asm/bL_switcher.h> + + +/* 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 struct cpufreq_frequency_table __read_mostly bl_freqs[] = { + { CLUSTER_BIG, FREQ_BIG }, + { CLUSTER_LITTLE, FREQ_LITTLE }, + { 0, CPUFREQ_TABLE_END }, +}; + +/* Cached current cluster for each CPU to save on IPIs */ +static DEFINE_PER_CPU(unsigned int, cpu_cur_cluster); + + +/* Miscellaneous helpers */ + +static unsigned int entry_to_freq( + struct cpufreq_frequency_table const *entry) +{ + return entry->frequency; +} + +static unsigned int entry_to_cluster( + struct cpufreq_frequency_table const *entry) +{ + return entry->index; +} + +static struct cpufreq_frequency_table const *find_entry_by_cluster(int cluster) +{ + unsigned int i; + + for(i = 0; entry_to_freq(&bl_freqs[i]) != CPUFREQ_TABLE_END; i++) + if(entry_to_cluster(&bl_freqs[i]) == cluster) + return &bl_freqs[i]; + + WARN(1, pr_fmt("%s(): invalid cluster number %d, assuming 0\n"), + __func__, cluster); + return &bl_freqs[0]; +} + +static unsigned int cluster_to_freq(int cluster) +{ + return entry_to_freq(find_entry_by_cluster(cluster)); +} + +/* + * Functions to get the current status. + * + * Beware that the cluster for another CPU may change unexpectedly. + */ + +static unsigned int get_local_cluster(void) +{ + unsigned int mpidr; + asm ("mrc\tp15, 0, %0, c0, c0, 5" : "=r" (mpidr)); + return MPIDR_AFFINITY_LEVEL(mpidr, 1); +} + +static void __get_current_cluster(void *_data) +{ + unsigned int *_cluster = _data; + *_cluster = get_local_cluster(); +} + +static int get_current_cluster(unsigned int cpu) +{ + unsigned int cluster = 0; + smp_call_function_single(cpu, __get_current_cluster, &cluster, 1); + return cluster; +} + +static int get_current_cached_cluster(unsigned int cpu) +{ + return per_cpu(cpu_cur_cluster, cpu); +} + +static unsigned int get_current_freq(unsigned int cpu) +{ + return cluster_to_freq(get_current_cluster(cpu)); +} + +/* + * Switch to the requested cluster. + */ +static void switch_to_entry(unsigned int cpu, + struct cpufreq_frequency_table const *target) +{ + int old_cluster, new_cluster; + struct cpufreq_freqs freqs; + + old_cluster = get_current_cached_cluster(cpu); + new_cluster = entry_to_cluster(target); + + pr_debug("Switching to cluster %d on CPU %d\n", new_cluster, cpu); + + if(new_cluster == old_cluster) + return; + + freqs.cpu = cpu; + freqs.old = cluster_to_freq(old_cluster); + freqs.new = entry_to_freq(target); + + cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE); + bL_switch_request(cpu, new_cluster); + per_cpu(cpu_cur_cluster, cpu) = new_cluster; + cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE); +} + + +/* Cpufreq methods and module code */ + +static int bl_cpufreq_init(struct cpufreq_policy *policy) +{ + unsigned int cluster, cpu = policy->cpu; + 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; + + cluster = get_current_cluster(cpu); + per_cpu(cpu_cur_cluster, cpu) = cluster; + + /* + * Ideally, transition_latency should be calibrated here. + */ + policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL; + policy->cur = cluster_to_freq(cluster); + policy->shared_type = CPUFREQ_SHARED_TYPE_NONE; + + pr_info("cpufreq initialised successfully\n"); + return 0; + +error: + pr_warning("cpufreq initialisation failed (%d)\n", 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; + + err = cpufreq_frequency_table_target(policy, bl_freqs, target_freq, + relation, &index); + if(err) + return err; + + switch_to_entry(policy->cpu, &bl_freqs[index]); + return 0; +} + +static unsigned int bl_cpufreq_get(unsigned int cpu) +{ + return get_current_freq(cpu); +} + +static struct cpufreq_driver __read_mostly bl_cpufreq_driver = { + .owner = THIS_MODULE, + .name = MODULE_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) + pr_info("cpufreq backend driver registration failed (%d)\n", + err); + else + pr_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); + pr_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"); |