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Subject[PATCH v3 21/22] cpufreq: add support for CPU DVFS based on SCMI message protocol
Date
On some ARM based systems, a separate Cortex-M based System Control
Processor(SCP) provides the overall power, clock, reset and system
control including CPU DVFS. SCMI Message Protocol is used to
communicate with the SCP.

This patch adds a cpufreq driver for such systems using SCMI interface
to drive CPU DVFS.

Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
MAINTAINERS | 2 +-
drivers/cpufreq/Kconfig.arm | 11 ++
drivers/cpufreq/Makefile | 1 +
drivers/cpufreq/scmi-cpufreq.c | 271 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 284 insertions(+), 1 deletion(-)
create mode 100644 drivers/cpufreq/scmi-cpufreq.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 32c184391aee..1733813c52d9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12942,7 +12942,7 @@ L: linux-arm-kernel@lists.infradead.org
S: Maintained
F: Documentation/devicetree/bindings/arm/arm,sc[mp]i.txt
F: drivers/clk/clk-sc[mp]i.c
-F: drivers/cpufreq/scpi-cpufreq.c
+F: drivers/cpufreq/sc[mp]i-cpufreq.c
F: drivers/firmware/arm_scpi.c
F: drivers/firmware/arm_scmi/
F: include/linux/sc[mp]i_protocol.h
diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index bdce4488ded1..e21f84cbd9b4 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -205,6 +205,17 @@ config ARM_SA1100_CPUFREQ
config ARM_SA1110_CPUFREQ
bool

+config ARM_SCMI_CPUFREQ
+ tristate "SCMI based CPUfreq driver"
+ depends on ARM_SCMI_PROTOCOL || COMPILE_TEST
+ select PM_OPP
+ help
+ This adds the CPUfreq driver support for ARM platforms using SCMI
+ protocol for CPU power management.
+
+ This driver uses SCMI Message Protocol driver to interact with the
+ firmware providing the CPU DVFS functionality.
+
config ARM_SCPI_CPUFREQ
tristate "SCPI based CPUfreq driver"
depends on ARM_BIG_LITTLE_CPUFREQ && ARM_SCPI_PROTOCOL && COMMON_CLK_SCPI
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index c7af9b2a255e..1206207f9b62 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -71,6 +71,7 @@ obj-$(CONFIG_ARM_S3C64XX_CPUFREQ) += s3c64xx-cpufreq.o
obj-$(CONFIG_ARM_S5PV210_CPUFREQ) += s5pv210-cpufreq.o
obj-$(CONFIG_ARM_SA1100_CPUFREQ) += sa1100-cpufreq.o
obj-$(CONFIG_ARM_SA1110_CPUFREQ) += sa1110-cpufreq.o
+obj-$(CONFIG_ARM_SCMI_CPUFREQ) += scmi-cpufreq.o
obj-$(CONFIG_ARM_SCPI_CPUFREQ) += scpi-cpufreq.o
obj-$(CONFIG_ARM_SPEAR_CPUFREQ) += spear-cpufreq.o
obj-$(CONFIG_ARM_STI_CPUFREQ) += sti-cpufreq.o
diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
new file mode 100644
index 000000000000..bc5385638eb4
--- /dev/null
+++ b/drivers/cpufreq/scmi-cpufreq.c
@@ -0,0 +1,271 @@
+/*
+ * System Control and Power Interface (SCMI) based CPUFreq Interface driver
+ *
+ * Copyright (C) 2017 ARM Ltd.
+ * Sudeep Holla <sudeep.holla@arm.com>
+ *
+ * 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/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/cpumask.h>
+#include <linux/cpu_cooling.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/slab.h>
+#include <linux/scmi_protocol.h>
+#include <linux/types.h>
+
+struct scmi_data {
+ int domain_id;
+ struct device *cpu_dev;
+ struct thermal_cooling_device *cdev;
+};
+
+static const struct scmi_handle *handle;
+
+unsigned int scmi_cpufreq_get_rate(unsigned int cpu)
+{
+ struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
+ struct scmi_perf_ops *perf_ops = handle->perf_ops;
+ struct scmi_data *priv = policy->driver_data;
+ unsigned long rate;
+ int ret;
+
+ ret = perf_ops->freq_get(handle, priv->domain_id, &rate, false);
+ if (ret)
+ return 0;
+ return rate / 1000;
+}
+
+/*
+ * perf_ops->freq_set is not a synchronous, the actual OPP change will
+ * happen asynchronously and can get notified if the events are
+ * subscribed for by the SCMI firmware
+ */
+static int
+scmi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
+{
+ struct scmi_data *priv = policy->driver_data;
+ struct scmi_perf_ops *perf_ops = handle->perf_ops;
+ u64 freq = policy->freq_table[index].frequency * 1000;
+
+ return perf_ops->freq_set(handle, priv->domain_id, freq, false);
+}
+
+static int
+scmi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
+{
+ int cpu, domain, tdomain;
+ struct device *tcpu_dev;
+
+ domain = handle->perf_ops->device_domain_id(cpu_dev);
+ if (domain < 0)
+ return domain;
+
+ for_each_possible_cpu(cpu) {
+ if (cpu == cpu_dev->id)
+ continue;
+
+ tcpu_dev = get_cpu_device(cpu);
+ if (!tcpu_dev)
+ continue;
+
+ tdomain = handle->perf_ops->device_domain_id(tcpu_dev);
+ if (tdomain == domain)
+ cpumask_set_cpu(cpu, cpumask);
+ }
+
+ return 0;
+}
+
+static int scmi_cpufreq_init(struct cpufreq_policy *policy)
+{
+ int ret;
+ unsigned int latency;
+ struct device *cpu_dev;
+ struct scmi_data *priv;
+ struct cpufreq_frequency_table *freq_table;
+
+ cpu_dev = get_cpu_device(policy->cpu);
+ if (!cpu_dev) {
+ pr_err("failed to get cpu%d device\n", policy->cpu);
+ return -ENODEV;
+ }
+
+ ret = handle->perf_ops->add_opps_to_device(cpu_dev);
+ if (ret) {
+ dev_warn(cpu_dev, "failed to add opps to the device\n");
+ return ret;
+ }
+
+ ret = scmi_get_sharing_cpus(cpu_dev, policy->cpus);
+ if (ret) {
+ dev_warn(cpu_dev, "failed to get sharing cpumask\n");
+ return ret;
+ }
+
+ ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
+ if (ret) {
+ dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
+ __func__, ret);
+ return ret;
+ }
+
+ /*
+ * We need OPP table to function and since OPPs are added by the
+ * platform, let's wait for the same.
+ */
+ ret = dev_pm_opp_get_opp_count(cpu_dev);
+ if (ret <= 0) {
+ dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
+ ret = -EPROBE_DEFER;
+ goto out_free_opp;
+ }
+
+ priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+ if (!priv) {
+ ret = -ENOMEM;
+ goto out_free_opp;
+ }
+
+ ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
+ if (ret) {
+ dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
+ goto out_free_priv;
+ }
+
+ priv->cpu_dev = cpu_dev;
+ priv->domain_id = handle->perf_ops->device_domain_id(cpu_dev);
+
+ policy->driver_data = priv;
+
+ ret = cpufreq_table_validate_and_show(policy, freq_table);
+ if (ret) {
+ dev_err(cpu_dev, "%s: invalid frequency table: %d\n", __func__,
+ ret);
+ goto out_free_cpufreq_table;
+ }
+
+ /* SCMI allows DVFS request for any domain from any CPU */
+ policy->dvfs_possible_from_any_cpu = true;
+
+ latency = handle->perf_ops->get_transition_latency(cpu_dev);
+ if (!latency)
+ latency = CPUFREQ_ETERNAL;
+
+ policy->cpuinfo.transition_latency = latency;
+
+ return 0;
+
+out_free_cpufreq_table:
+ dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
+out_free_priv:
+ kfree(priv);
+out_free_opp:
+ dev_pm_opp_cpumask_remove_table(policy->cpus);
+
+ return ret;
+}
+
+static int scmi_cpufreq_exit(struct cpufreq_policy *policy)
+{
+ struct scmi_data *priv = policy->driver_data;
+
+ cpufreq_cooling_unregister(priv->cdev);
+ dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
+ kfree(priv);
+ dev_pm_opp_cpumask_remove_table(policy->related_cpus);
+
+ return 0;
+}
+
+static void scmi_cpufreq_ready(struct cpufreq_policy *policy)
+{
+ struct scmi_data *priv = policy->driver_data;
+ struct device_node *np = of_node_get(priv->cpu_dev->of_node);
+
+ if (WARN_ON(!np))
+ return;
+
+ if (of_find_property(np, "#cooling-cells", NULL)) {
+ u32 pcoeff = 0;
+
+ of_property_read_u32(np, "dynamic-power-coefficient",
+ &pcoeff);
+
+ priv->cdev = of_cpufreq_power_cooling_register(np, policy,
+ pcoeff, NULL);
+ if (IS_ERR(priv->cdev)) {
+ dev_err(priv->cpu_dev,
+ "running cpufreq without cooling device: %ld\n",
+ PTR_ERR(priv->cdev));
+
+ priv->cdev = NULL;
+ }
+ }
+
+ of_node_put(np);
+}
+
+static struct cpufreq_driver scmi_cpufreq_driver = {
+ .name = "scmi",
+ .flags = CPUFREQ_STICKY | CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
+ CPUFREQ_NEED_INITIAL_FREQ_CHECK,
+ .verify = cpufreq_generic_frequency_table_verify,
+ .attr = cpufreq_generic_attr,
+ .target_index = scmi_cpufreq_set_target,
+ .get = scmi_cpufreq_get_rate,
+ .init = scmi_cpufreq_init,
+ .exit = scmi_cpufreq_exit,
+ .ready = scmi_cpufreq_ready,
+};
+
+static int scmi_cpufreq_probe(struct platform_device *pdev)
+{
+ int ret;
+
+ handle = devm_scmi_handle_get(&pdev->dev);
+
+ if (IS_ERR_OR_NULL(handle) || !handle->perf_ops)
+ return -EPROBE_DEFER;
+
+ ret = cpufreq_register_driver(&scmi_cpufreq_driver);
+ if (ret) {
+ dev_err(&pdev->dev, "%s: registering cpufreq failed, err: %d\n",
+ __func__, ret);
+ }
+
+ return ret;
+}
+
+static int scmi_cpufreq_remove(struct platform_device *pdev)
+{
+ cpufreq_unregister_driver(&scmi_cpufreq_driver);
+ return 0;
+}
+
+static struct platform_driver scmi_cpufreq_platdrv = {
+ .driver = {
+ .name = "scmi-cpufreq",
+ },
+ .probe = scmi_cpufreq_probe,
+ .remove = scmi_cpufreq_remove,
+};
+module_platform_driver(scmi_cpufreq_platdrv);
+
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
+MODULE_DESCRIPTION("ARM SCMI CPUFreq interface driver");
+MODULE_LICENSE("GPL v2");
--
2.7.4
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