Re: [PATCH v2 5/5] cpufreq: arm_big_little: add SCPI interface driver

[Rafael J. Wysocki]

On Thursday, May 14, 2015 04:42:35 PM Sudeep Holla wrote:
> 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@xxxxxxx>
> Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx
> ---
>  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..443570801229
> --- /dev/null
> +++ b/drivers/cpufreq/scpi-cpufreq.c
> @@ -0,0 +1,124 @@
> +/*
> + * SCPI CPUFreq Interface driver

It would be good to expand the TLA here IMO.

The rest I'm leaving to Viresh. :-)

> + *
> + * It provides necessary ops to arm_big_little cpufreq driver.
> + *
> + * Copyright (C) 2015 ARM Ltd.
> + * Sudeep Holla <sudeep.holla@xxxxxxx>
> + *
> + * 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@xxxxxxx>");
> +MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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