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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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      Last update: 2017-09-28 15:16    [W:7.593 / U:0.460 seconds]
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