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    Subject[PATCH v4 5/8] cpufreq: arm_big_little: add SCPI interface driver
    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. SCPI Message Protocol is used to
    communicate with the SCPI.

    This patch adds a interface driver for adding OPPs and registering
    the arm_big_little cpufreq driver for such systems.

    Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
    Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
    Cc: Viresh Kumar <viresh.kumar@linaro.org>
    Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
    Cc: linux-pm@vger.kernel.org
    ---
    drivers/cpufreq/Kconfig.arm | 9 +++
    drivers/cpufreq/Makefile | 1 +
    drivers/cpufreq/scpi-cpufreq.c | 124 +++++++++++++++++++++++++++++++++++++++++
    3 files changed, 134 insertions(+)
    create mode 100644 drivers/cpufreq/scpi-cpufreq.c

    diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
    index 611cb09239eb..6419b17b89dd 100644
    --- a/drivers/cpufreq/Kconfig.arm
    +++ b/drivers/cpufreq/Kconfig.arm
    @@ -24,6 +24,15 @@ config ARM_VEXPRESS_SPC_CPUFREQ
    This add the CPUfreq driver support for Versatile Express
    big.LITTLE platforms using SPC for power management.

    +config ARM_SCPI_CPUFREQ
    + tristate "SCPI based CPUfreq driver"
    + depends on ARM_BIG_LITTLE_CPUFREQ && ARM_SCPI_PROTOCOL
    + help
    + This adds the CPUfreq driver support for ARM big.LITTLE platforms
    + using SCPI protocol for CPU power management.
    +
    + This driver uses SCPI Message Protocol driver to interact with the
    + firmware providing the CPU DVFS functionality.

    config ARM_EXYNOS_CPUFREQ
    tristate "SAMSUNG EXYNOS CPUfreq Driver"
    diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
    index cdce92ae2e8b..02fc9f849d4b 100644
    --- a/drivers/cpufreq/Makefile
    +++ b/drivers/cpufreq/Makefile
    @@ -79,6 +79,7 @@ obj-$(CONFIG_ARM_SA1110_CPUFREQ) += sa1110-cpufreq.o
    obj-$(CONFIG_ARM_SPEAR_CPUFREQ) += spear-cpufreq.o
    obj-$(CONFIG_ARM_TEGRA_CPUFREQ) += tegra-cpufreq.o
    obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ) += vexpress-spc-cpufreq.o
    +obj-$(CONFIG_ARM_SCPI_CPUFREQ) += scpi-cpufreq.o

    ##################################################################################
    # PowerPC platform drivers
    diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
    new file mode 100644
    index 000000000000..2c3b16fd3a01
    --- /dev/null
    +++ b/drivers/cpufreq/scpi-cpufreq.c
    @@ -0,0 +1,124 @@
    +/*
    + * System Control and Power Interface (SCPI) based CPUFreq Interface driver
    + *
    + * It provides necessary ops to arm_big_little cpufreq driver.
    + *
    + * Copyright (C) 2015 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/cpufreq.h>
    +#include <linux/module.h>
    +#include <linux/platform_device.h>
    +#include <linux/pm_opp.h>
    +#include <linux/scpi_protocol.h>
    +#include <linux/types.h>
    +
    +#include "arm_big_little.h"
    +
    +static struct scpi_ops *scpi_ops;
    +
    +static struct scpi_dvfs_info *scpi_get_dvfs_info(struct device *cpu_dev)
    +{
    + u8 domain = topology_physical_package_id(cpu_dev->id);
    +
    + if (domain < 0)
    + return ERR_PTR(-EINVAL);
    + return scpi_ops->dvfs_get_info(domain);
    +}
    +
    +static int scpi_opp_table_ops(struct device *cpu_dev, bool remove)
    +{
    + int idx, ret = 0;
    + struct scpi_opp *opp;
    + struct scpi_dvfs_info *info = scpi_get_dvfs_info(cpu_dev);
    +
    + if (IS_ERR(info))
    + return PTR_ERR(info);
    +
    + if (!info->opps)
    + return -EIO;
    +
    + for (opp = info->opps, idx = 0; idx < info->count; idx++, opp++) {
    + if (remove)
    + dev_pm_opp_remove(cpu_dev, opp->freq);
    + else
    + ret = dev_pm_opp_add(cpu_dev, opp->freq,
    + opp->m_volt * 1000);
    + if (ret) {
    + dev_warn(cpu_dev, "failed to add opp %uHz %umV\n",
    + opp->freq, opp->m_volt);
    + while (idx-- > 0)
    + dev_pm_opp_remove(cpu_dev, (--opp)->freq);
    + return ret;
    + }
    + }
    + return ret;
    +}
    +
    +static int scpi_get_transition_latency(struct device *cpu_dev)
    +{
    + struct scpi_dvfs_info *info = scpi_get_dvfs_info(cpu_dev);
    +
    + if (IS_ERR(info))
    + return PTR_ERR(info);
    + return info->latency;
    +}
    +
    +static int scpi_init_opp_table(struct device *cpu_dev)
    +{
    + return scpi_opp_table_ops(cpu_dev, false);
    +}
    +
    +static void scpi_free_opp_table(struct device *cpu_dev)
    +{
    + scpi_opp_table_ops(cpu_dev, true);
    +}
    +
    +static struct cpufreq_arm_bL_ops scpi_cpufreq_ops = {
    + .name = "scpi",
    + .get_transition_latency = scpi_get_transition_latency,
    + .init_opp_table = scpi_init_opp_table,
    + .free_opp_table = scpi_free_opp_table,
    +};
    +
    +static int scpi_cpufreq_probe(struct platform_device *pdev)
    +{
    + scpi_ops = get_scpi_ops();
    + if (!scpi_ops)
    + return -EIO;
    +
    + return bL_cpufreq_register(&scpi_cpufreq_ops);
    +}
    +
    +static int scpi_cpufreq_remove(struct platform_device *pdev)
    +{
    + bL_cpufreq_unregister(&scpi_cpufreq_ops);
    + scpi_ops = NULL;
    + return 0;
    +}
    +
    +static struct platform_driver scpi_cpufreq_platdrv = {
    + .driver = {
    + .name = "scpi-cpufreq",
    + .owner = THIS_MODULE,
    + },
    + .probe = scpi_cpufreq_probe,
    + .remove = scpi_cpufreq_remove,
    +};
    +module_platform_driver(scpi_cpufreq_platdrv);
    +
    +MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
    +MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
    +MODULE_LICENSE("GPL v2");
    --
    1.9.1


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