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authorDave Martin <dave.martin@linaro.org>2012-03-16 17:53:43 +0000
committerAndrey Konovalov <andrey.konovalov@linaro.org>2013-05-25 12:58:32 +0400
commitfdde7baf98fadd7b7df54242f0403b77e1c55b9c (patch)
treebec597ca7ec5d4b4007f9e61586d1e39b5d7ad32
parent256e5d8c3f7bae348b2115e0323ef9e836eb4d47 (diff)
downloadvexpress-lsk-fdde7baf98fadd7b7df54242f0403b77e1c55b9c.tar.gz
cpufreq/arm-bl-cpufreq: Add simple cpufreq big.LITTLE switcher frontend
This patch adds a very simple cpufreq-based frontend to the ARM big.LITTLE switcher. This driver simply simulates two performance points corresponding to the big and little clusters. There is currently no interface for reporting what the dummy frequencies exposed by the driver actually mean in terms of real cluster / performance point combinations. For the very simple case supported, cpuinfo_max_freq corresponds to big and cpuinfo_min_freq corresponds to LITTLE. Signed-off-by: Dave Martin <dave.martin@linaro.org>
-rw-r--r--Documentation/cpu-freq/cpufreq-arm-bl.txt47
-rw-r--r--drivers/cpufreq/Kconfig.arm12
-rw-r--r--drivers/cpufreq/Makefile3
-rw-r--r--drivers/cpufreq/arm-bl-cpufreq.c244
4 files changed, 305 insertions, 1 deletions
diff --git a/Documentation/cpu-freq/cpufreq-arm-bl.txt b/Documentation/cpu-freq/cpufreq-arm-bl.txt
new file mode 100644
index 00000000000..52e2f3ad761
--- /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 $little_freq >/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
+}
diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 6ef9c7b0691..97dd3fc49a3 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -2,6 +2,18 @@
# ARM CPU Frequency scaling drivers
#
+config ARM_BL_CPUFREQ
+ depends on EXPERIMENTAL
+ depends on BL_SWITCHER
+ tristate "Simple cpufreq interface for the ARM big.LITTLE switcher"
+ help
+ Provides a simple cpufreq interface to control the ARM
+ big.LITTLE switcher.
+
+ Refer to Documentation/cpu-freq/cpufreq-arm-bl.txt for details.
+
+ If unsure, say N.
+
config ARM_OMAP2PLUS_CPUFREQ
bool "TI OMAP2+"
depends on ARCH_OMAP2PLUS
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 6148eac24fc..3bcc6a11589 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -44,7 +44,8 @@ obj-$(CONFIG_X86_INTEL_PSTATE) += intel_pstate.o
##################################################################################
# ARM SoC drivers
-obj-$(CONFIG_UX500_SOC_DB8500) += dbx500-cpufreq.o
+obj-$(CONFIG_UX500_SOC_DB8500) += db8500-cpufreq.o
+obj-$(CONFIG_ARM_BL_CPUFREQ) += arm-bl-cpufreq.o
obj-$(CONFIG_ARM_S3C2416_CPUFREQ) += s3c2416-cpufreq.o
obj-$(CONFIG_ARM_S3C64XX_CPUFREQ) += s3c64xx-cpufreq.o
obj-$(CONFIG_ARM_S5PV210_CPUFREQ) += s5pv210-cpufreq.o
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");