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Subject[PATCH] cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue
Date
big LITTLE is ARM's new Architecture focussing power/performance needs of modern
world. More information about big LITTLE can be found here:

http://www.arm.com/products/processors/technologies/biglittleprocessing.php
http://lwn.net/Articles/481055/

In order to keep cpufreq support for all big LITTLE platforms simple/generic,
this patch tries to add a generic cpufreq driver layer for all big LITTLE
platforms.

The driver is divided into two parts:
- Core driver: Generic and shared across all big LITTLE SoC's
- Glue drivers: Per platform drivers providing ops to the core driver

This patch adds in a generic glue driver which would extract information from
Device Tree.

Future SoC's can either reuse the DT glue or write their own depending on the
need.

Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
This is pushed here:

http://git.linaro.org/gitweb?p=people/vireshk/linux.git;a=shortlog;h=refs/heads/cpufreq-biglittle

.../bindings/cpufreq/arm_big_little_dt.txt | 29 +++
MAINTAINERS | 11 +
drivers/cpufreq/Kconfig.arm | 13 +
drivers/cpufreq/Makefile | 4 +
drivers/cpufreq/arm_big_little.c | 278 +++++++++++++++++++++
drivers/cpufreq/arm_big_little.h | 40 +++
drivers/cpufreq/arm_big_little_dt.c | 125 +++++++++
7 files changed, 500 insertions(+)
create mode 100644 Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt
create mode 100644 drivers/cpufreq/arm_big_little.c
create mode 100644 drivers/cpufreq/arm_big_little.h
create mode 100644 drivers/cpufreq/arm_big_little_dt.c
diff --git a/Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt b/Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt
new file mode 100644
index 0000000..6f534eb
--- /dev/null
+++ b/Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt
@@ -0,0 +1,29 @@
+Generic ARM big LITTLE cpufreq driver's DT glue
+-----------------------------------------------
+
+It is DT specific glue layer for generic cpufreq driver for big LITTLE systems.
+
+Both required and optional properties listed below must be defined under node
+cluster*. * can be 0 or 1.
+
+Required properties:
+- freqs: List of all supported frequencies.
+
+Optional properties:
+- clock-latency: Specify the possible maximum transition latency for clock, in
+ unit of nanoseconds.
+
+Examples:
+
+cluster0: cluster@0 {
+ ..
+
+ freqs = <500000000 600000000 700000000 800000000 900000000 1000000000 1100000000 1200000000>;
+ clock-latency = <200000>;
+
+ ..
+
+ cores {
+ ..
+ };
+};
diff --git a/MAINTAINERS b/MAINTAINERS
index 554fd30..b14b749 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2206,6 +2206,17 @@ S: Maintained
F: drivers/cpufreq/
F: include/linux/cpufreq.h

+CPU FREQUENCY DRIVERS - ARM BIG LITTLE
+M: Viresh Kumar <viresh.kumar@linaro.org>
+M: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
+L: cpufreq@vger.kernel.org
+L: linux-pm@vger.kernel.org
+W: http://www.arm.com/products/processors/technologies/biglittleprocessing.php
+S: Maintained
+F: drivers/cpufreq/arm_big_little.h
+F: drivers/cpufreq/arm_big_little.c
+F: drivers/cpufreq/arm_big_little_dt.c
+
CPUID/MSR DRIVER
M: "H. Peter Anvin" <hpa@zytor.com>
S: Maintained
diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 030ddf6..fdf54a9 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -2,6 +2,19 @@
# ARM CPU Frequency scaling drivers
#

+config ARM_BIG_LITTLE_CPUFREQ
+ tristate
+ depends on ARM_CPU_TOPOLOGY
+
+config ARM_DT_BL_CPUFREQ
+ tristate "Generic ARM big LITTLE CPUfreq driver probed via DT"
+ select ARM_BIG_LITTLE_CPUFREQ
+ depends on OF
+ default n
+ help
+ This enables the Generic CPUfreq driver for ARM big.LITTLE platform.
+ This gets frequency tables from DT.
+
config ARM_OMAP2PLUS_CPUFREQ
bool "TI OMAP2+"
depends on ARCH_OMAP2PLUS
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 863fd18..d1b0832 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -44,6 +44,10 @@ obj-$(CONFIG_X86_INTEL_PSTATE) += intel_pstate.o

##################################################################################
# ARM SoC drivers
+obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ) += arm_big_little.o
+# big LITTLE per platform glues. Keep DT_BL_CPUFREQ as the last entry in all big
+# LITTLE drivers, so that it is probed last.
+obj-$(CONFIG_ARM_DT_BL_CPUFREQ) += arm_big_little_dt.o
obj-$(CONFIG_UX500_SOC_DB8500) += dbx500-cpufreq.o
obj-$(CONFIG_ARM_S3C2416_CPUFREQ) += s3c2416-cpufreq.o
obj-$(CONFIG_ARM_S3C64XX_CPUFREQ) += s3c64xx-cpufreq.o
diff --git a/drivers/cpufreq/arm_big_little.c b/drivers/cpufreq/arm_big_little.c
new file mode 100644
index 0000000..0d6de0e
--- /dev/null
+++ b/drivers/cpufreq/arm_big_little.c
@@ -0,0 +1,278 @@
+/*
+ * ARM big.LITTLE Platforms CPUFreq support
+ *
+ * Copyright (C) 2013 ARM Ltd.
+ * Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
+ *
+ * Copyright (C) 2013 Linaro.
+ * Viresh Kumar <viresh.kumar@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/clk.h>
+#include <linux/cpufreq.h>
+#include <linux/cpumask.h>
+#include <linux/export.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+#include <linux/topology.h>
+#include <linux/types.h>
+
+#include "arm_big_little.h"
+
+/* Currently we support only two clusters */
+#define MAX_CLUSTERS 2
+
+static struct cpufreq_arm_bL_ops *arm_bL_ops;
+static struct clk *clk[MAX_CLUSTERS];
+static struct cpufreq_frequency_table *freq_table[MAX_CLUSTERS];
+static atomic_t cluster_usage[MAX_CLUSTERS] = {ATOMIC_INIT(0), ATOMIC_INIT(0)};
+
+static int cpu_to_cluster(int cpu)
+{
+ return topology_physical_package_id(cpu);
+}
+
+static unsigned int bL_cpufreq_get(unsigned int cpu)
+{
+ u32 cur_cluster = cpu_to_cluster(cpu);
+
+ return clk_get_rate(clk[cur_cluster]) / 1000;
+}
+
+/* Validate policy frequency range */
+static int bL_cpufreq_verify_policy(struct cpufreq_policy *policy)
+{
+ u32 cur_cluster = cpu_to_cluster(policy->cpu);
+
+ return cpufreq_frequency_table_verify(policy, freq_table[cur_cluster]);
+}
+
+/* Set clock frequency */
+static int bL_cpufreq_set_target(struct cpufreq_policy *policy,
+ unsigned int target_freq, unsigned int relation)
+{
+ struct cpufreq_freqs freqs;
+ u32 cpu = policy->cpu, freq_tab_idx, cur_cluster;
+ int ret = 0;
+
+ cur_cluster = cpu_to_cluster(policy->cpu);
+
+ freqs.old = bL_cpufreq_get(policy->cpu);
+
+ /* Determine valid target frequency using freq_table */
+ cpufreq_frequency_table_target(policy, freq_table[cur_cluster],
+ target_freq, relation, &freq_tab_idx);
+ freqs.new = freq_table[cur_cluster][freq_tab_idx].frequency;
+
+ freqs.cpu = policy->cpu;
+
+ pr_debug("%s: cpu: %d, cluster: %d, oldfreq: %d, target freq: %d, new freq: %d\n",
+ __func__, cpu, cur_cluster, freqs.old, target_freq,
+ freqs.new);
+
+ if (freqs.old == freqs.new)
+ return 0;
+
+ for_each_cpu(freqs.cpu, policy->cpus)
+ cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+
+ ret = clk_set_rate(clk[cur_cluster], freqs.new * 1000);
+ if (ret) {
+ pr_err("clk_set_rate failed: %d\n", ret);
+ return ret;
+ }
+
+ policy->cur = freqs.new;
+
+ for_each_cpu(freqs.cpu, policy->cpus)
+ cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+
+ return ret;
+}
+
+/* translate the integer array into cpufreq_frequency_table entries */
+struct cpufreq_frequency_table *
+arm_bL_copy_table_from_array(unsigned int *table, int count)
+{
+ int i;
+
+ struct cpufreq_frequency_table *freq_table;
+
+ pr_debug("%s: table: %p, count: %d\n", __func__, table, count);
+
+ freq_table = kmalloc(sizeof(*freq_table) * (count + 1), GFP_KERNEL);
+ if (!freq_table)
+ return NULL;
+
+ for (i = 0; i < count; i++) {
+ pr_debug("%s: index: %d, freq: %d\n", __func__, i, table[i]);
+ freq_table[i].index = i;
+ freq_table[i].frequency = table[i]; /* in kHZ */
+ }
+
+ freq_table[i].index = count;
+ freq_table[i].frequency = CPUFREQ_TABLE_END;
+
+ return freq_table;
+}
+EXPORT_SYMBOL_GPL(arm_bL_copy_table_from_array);
+
+void arm_bL_free_freq_table(u32 cluster)
+{
+ pr_debug("%s: free freq table\n", __func__);
+
+ kfree(freq_table[cluster]);
+}
+EXPORT_SYMBOL_GPL(arm_bL_free_freq_table);
+
+static void put_cluster_clk_and_freq_table(u32 cluster)
+{
+ if (!atomic_dec_return(&cluster_usage[cluster])) {
+ clk_put(clk[cluster]);
+ clk[cluster] = NULL;
+ arm_bL_ops->put_freq_tbl(cluster);
+ freq_table[cluster] = NULL;
+ pr_debug("%s: cluster: %d\n", __func__, cluster);
+ }
+}
+
+static int get_cluster_clk_and_freq_table(u32 cluster)
+{
+ char name[9] = "cluster";
+ int count;
+
+ if (atomic_inc_return(&cluster_usage[cluster]) != 1)
+ return 0;
+
+ freq_table[cluster] = arm_bL_ops->get_freq_tbl(cluster, &count);
+ if (!freq_table[cluster])
+ goto atomic_dec;
+
+ name[7] = cluster + '0';
+ clk[cluster] = clk_get(NULL, name);
+ if (!IS_ERR_OR_NULL(clk[cluster])) {
+ pr_debug("%s: clk: %p & freq table: %p, cluster: %d\n",
+ __func__, clk[cluster], freq_table[cluster],
+ cluster);
+ return 0;
+ }
+
+ arm_bL_ops->put_freq_tbl(cluster);
+
+atomic_dec:
+ atomic_dec(&cluster_usage[cluster]);
+ pr_err("%s: Failed to get data for cluster: %d\n", __func__, cluster);
+ return -ENODATA;
+}
+
+/* Per-CPU initialization */
+static int bL_cpufreq_init(struct cpufreq_policy *policy)
+{
+ u32 cur_cluster = cpu_to_cluster(policy->cpu);
+ int result;
+
+ result = get_cluster_clk_and_freq_table(cur_cluster);
+ if (result)
+ return result;
+
+ result = cpufreq_frequency_table_cpuinfo(policy,
+ freq_table[cur_cluster]);
+ if (result) {
+ pr_err("CPU %d, cluster: %d invalid freq table\n", policy->cpu,
+ cur_cluster);
+ put_cluster_clk_and_freq_table(cur_cluster);
+ return result;
+ }
+
+ cpufreq_frequency_table_get_attr(freq_table[cur_cluster], policy->cpu);
+
+ policy->cpuinfo.transition_latency =
+ arm_bL_ops->get_transition_latency(cur_cluster);
+ policy->cur = bL_cpufreq_get(policy->cpu);
+
+ cpumask_copy(policy->cpus, topology_core_cpumask(policy->cpu));
+
+ pr_info("CPU %d initialized\n", policy->cpu);
+ return 0;
+}
+
+static int bL_cpufreq_exit(struct cpufreq_policy *policy)
+{
+ put_cluster_clk_and_freq_table(cpu_to_cluster(policy->cpu));
+ pr_debug("%s: Exited, cpu: %d\n", __func__, policy->cpu);
+
+ return 0;
+}
+
+/* Export freq_table to sysfs */
+static struct freq_attr *bL_cpufreq_attr[] = {
+ &cpufreq_freq_attr_scaling_available_freqs,
+ NULL,
+};
+
+static struct cpufreq_driver bL_cpufreq_driver = {
+ .name = "arm-big-little",
+ .flags = CPUFREQ_STICKY,
+ .verify = bL_cpufreq_verify_policy,
+ .target = bL_cpufreq_set_target,
+ .get = bL_cpufreq_get,
+ .init = bL_cpufreq_init,
+ .exit = bL_cpufreq_exit,
+ .attr = bL_cpufreq_attr,
+};
+
+int bL_cpufreq_register(struct cpufreq_arm_bL_ops *ops)
+{
+ int ret;
+
+ if (arm_bL_ops) {
+ pr_debug("%s: Already registered: %s, exiting\n", __func__,
+ arm_bL_ops->name);
+ return -EBUSY;
+ }
+
+ if (!ops || !strlen(ops->name) || !ops->get_freq_tbl) {
+ pr_err("%s: Invalid arm_bL_ops, exiting\n", __func__);
+ return -ENODEV;
+ }
+
+ arm_bL_ops = ops;
+
+ ret = cpufreq_register_driver(&bL_cpufreq_driver);
+ if (ret) {
+ pr_info("%s: Failed registering platform driver: %s, err: %d\n",
+ __func__, ops->name, ret);
+ arm_bL_ops = NULL;
+ } else {
+ pr_info("%s: Registered platform driver: %s\n", __func__,
+ ops->name);
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(bL_cpufreq_register);
+
+void bL_cpufreq_unregister(struct cpufreq_arm_bL_ops *ops)
+{
+ if (arm_bL_ops != ops) {
+ pr_info("%s: Registered with: %s, can't unregister, exiting\n",
+ __func__, arm_bL_ops->name);
+ }
+
+ cpufreq_unregister_driver(&bL_cpufreq_driver);
+ pr_info("%s: Un-registered platform driver: %s\n", __func__,
+ arm_bL_ops->name);
+ arm_bL_ops = NULL;
+}
+EXPORT_SYMBOL_GPL(bL_cpufreq_unregister);
diff --git a/drivers/cpufreq/arm_big_little.h b/drivers/cpufreq/arm_big_little.h
new file mode 100644
index 0000000..049e15d
--- /dev/null
+++ b/drivers/cpufreq/arm_big_little.h
@@ -0,0 +1,40 @@
+/*
+ * ARM big.LITTLE platform's CPUFreq header file
+ *
+ * Copyright (C) 2013 ARM Ltd.
+ * Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
+ *
+ * Copyright (C) 2013 Linaro.
+ * Viresh Kumar <viresh.kumar@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+#ifndef CPUFREQ_ARM_BIG_LITTLE_H
+#define CPUFREQ_ARM_BIG_LITTLE_H
+
+#include <linux/cpufreq.h>
+#include <linux/types.h>
+
+struct cpufreq_arm_bL_ops {
+ char name[CPUFREQ_NAME_LEN];
+ u32 (*get_transition_latency)(u32 cluster);
+ struct cpufreq_frequency_table *(*get_freq_tbl)(u32 cluster,
+ int *count);
+ void (*put_freq_tbl)(u32 cluster);
+};
+
+struct cpufreq_frequency_table *
+arm_bL_copy_table_from_array(unsigned int *table, int count);
+void arm_bL_free_freq_table(u32 cluster);
+
+int bL_cpufreq_register(struct cpufreq_arm_bL_ops *ops);
+void bL_cpufreq_unregister(struct cpufreq_arm_bL_ops *ops);
+
+#endif /* CPUFREQ_ARM_BIG_LITTLE_H */
diff --git a/drivers/cpufreq/arm_big_little_dt.c b/drivers/cpufreq/arm_big_little_dt.c
new file mode 100644
index 0000000..c1eee50
--- /dev/null
+++ b/drivers/cpufreq/arm_big_little_dt.c
@@ -0,0 +1,125 @@
+/*
+ * Generic big.LITTLE CPUFreq Interface driver
+ *
+ * It provides necessary ops to arm_big_little cpufreq driver and gets
+ * Frequency information from Device Tree. Freq table in DT must be in KHz.
+ *
+ * Copyright (C) 2013 Linaro.
+ * Viresh Kumar <viresh.kumar@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cpufreq.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include "arm_big_little.h"
+
+static struct cpufreq_frequency_table *generic_get_freq_tbl(u32 cluster,
+ int *count)
+{
+ struct device_node *np = NULL;
+ const struct property *pp;
+ unsigned int *table = NULL;
+ int cluster_id;
+ struct cpufreq_frequency_table *cpufreq_table;
+
+ while ((np = of_find_node_by_name(np, "cluster"))) {
+ if (of_property_read_u32(np, "reg", &cluster_id))
+ continue;
+
+ if (cluster_id != cluster)
+ continue;
+
+ pp = of_find_property(np, "freqs", NULL);
+ if (!pp)
+ continue;
+
+ *count = pp->length / sizeof(u32);
+ if (!*count)
+ continue;
+
+ table = kmalloc(sizeof(*table) * (*count), GFP_KERNEL);
+ if (!table) {
+ pr_err("%s: Failed to allocate memory for table\n",
+ __func__);
+ return NULL;
+ }
+
+ of_property_read_u32_array(np, "freqs", table, *count);
+ break;
+ }
+
+ if (!table) {
+ pr_err("%s: Unable to retrieve Freq table from Device Tree",
+ __func__);
+ return NULL;
+ }
+
+ cpufreq_table = arm_bL_copy_table_from_array(table, *count);
+ kfree(table);
+
+ return cpufreq_table;
+}
+
+static void generic_put_freq_tbl(u32 cluster)
+{
+ arm_bL_free_freq_table(cluster);
+}
+
+static u32 get_transition_latency(u32 cluster)
+{
+ struct device_node *np = NULL;
+ u32 transition_latency = CPUFREQ_ETERNAL;
+ int cluster_id;
+
+ while ((np = of_find_node_by_name(np, "cluster"))) {
+ if (of_property_read_u32(np, "reg", &cluster_id))
+ continue;
+
+ if (cluster_id != cluster)
+ continue;
+
+ of_property_read_u32(np, "clock-latency", &transition_latency);
+ return transition_latency;
+ }
+
+ pr_err("%s: Unable to get clock-latency from DT, use CPUFREQ_ETERNAL",
+ __func__);
+
+ return transition_latency;
+}
+
+static struct cpufreq_arm_bL_ops generic_bL_ops = {
+ .name = "generic-bl",
+ .get_transition_latency = get_transition_latency,
+ .get_freq_tbl = generic_get_freq_tbl,
+ .put_freq_tbl = generic_put_freq_tbl,
+};
+
+static int generic_bL_init(void)
+{
+ return bL_cpufreq_register(&generic_bL_ops);
+}
+module_init(generic_bL_init);
+
+static void generic_bL_exit(void)
+{
+ return bL_cpufreq_unregister(&generic_bL_ops);
+}
+module_exit(generic_bL_exit);
+
+MODULE_DESCRIPTION("Generic ARM big LITTLE cpufreq driver");
+MODULE_LICENSE("GPL");
--
1.7.12.rc2.18.g61b472e


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