Re: [PATCH 3/3] cpufreq: Add a generic cpufreq-cpu0 driver

[Richard Zhao <richard.zhao@freescale.com>]

On Thu, Jul 19, 2012 at 11:54:41PM +0800, Shawn Guo wrote:
> It adds a generic cpufreq driver for CPU0 frequency management based on
> clk, regulator, OPP and device tree support.  It can support both
> uniprocessor (UP) and those symmetric multiprocessor (SMP) systems which
> share clock and voltage across all CPUs.
> 
> Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
> ---
>  .../devicetree/bindings/cpufreq/cpufreq-cpu0.txt   |   58 +++++
>  drivers/cpufreq/Kconfig                            |   11 +
>  drivers/cpufreq/Makefile                           |    2 +
>  drivers/cpufreq/cpufreq-cpu0.c                     |  235 ++++++++++++++++++++
>  4 files changed, 306 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
>  create mode 100644 drivers/cpufreq/cpufreq-cpu0.c
> 
> diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
> new file mode 100644
> index 0000000..94799bc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
> @@ -0,0 +1,58 @@
> +Generic cpufreq driver for CPU0
It's going to have generic name if it will become more generic.

> +
> +It is a generic cpufreq driver for CPU0 frequency management.  It
> +supports both uniprocessor (UP) and symmetric multiprocessor (SMP)
> +systems which share clock and voltage across all CPUs.
> +
> +Both required and optional properties listed below must be defined
> +under node /cpus/cpu@0.
> +
> +Required properties:
> +- operating-points: Refer to Documentation/devicetree/bindings/power/opp.txt
> +  for details
> +
> +Optional properties:
> +- transition-latency: Specify the possible maximum transition latency,
> +  in unit of nanoseconds.
> +- voltage-tolerance: Specify the CPU voltage tolerance in percentage.
Why do we have the same tolerance for all points? I think you can
either remove tolerance or add it to opps.
> +
> +Examples:
> +
> +cpus {
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +
> +	cpu@0 {
> +		compatible = "arm,cortex-a9";
> +		reg = <0>;
> +		next-level-cache = <&L2>;
> +		operating-points = <
> +			/* kHz    uV    en */
> +			1200000 1275000 0
> +			996000  1225000 1
> +			792000  1100000 1
> +			672000  1100000 0
> +			396000  950000  1
> +			198000  850000  1
> +		>;
> +		transition-latency = <61036>; /* two CLK32 periods */
> +	};
> +
> +	cpu@1 {
> +		compatible = "arm,cortex-a9";
> +		reg = <1>;
> +		next-level-cache = <&L2>;
> +	};
> +
> +	cpu@2 {
> +		compatible = "arm,cortex-a9";
> +		reg = <2>;
> +		next-level-cache = <&L2>;
> +	};
> +
> +	cpu@3 {
> +		compatible = "arm,cortex-a9";
> +		reg = <3>;
> +		next-level-cache = <&L2>;
> +	};
> +};
> diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> index e24a2a1..e77a1e0 100644
> --- a/drivers/cpufreq/Kconfig
> +++ b/drivers/cpufreq/Kconfig
> @@ -179,6 +179,17 @@ config CPU_FREQ_GOV_CONSERVATIVE
>  
>  	  If in doubt, say N.
>  
> +config GENERIC_CPUFREQ_CPU0
> +	bool "Generic cpufreq driver for CPU0"
> +	depends on HAVE_CLK && REGULATOR && PM_OPP && OF
> +	select CPU_FREQ_TABLE
> +	help
> +	  This adds a generic cpufreq driver for CPU0 frequency management.
> +	  It supports both uniprocessor (UP) and symmetric multiprocessor (SMP)
> +	  systems which share clock and voltage across all CPUs.
> +
> +	  If in doubt, say N.
> +
>  menu "x86 CPU frequency scaling drivers"
>  depends on X86
>  source "drivers/cpufreq/Kconfig.x86"
> diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> index 9531fc2..a378ed2 100644
> --- a/drivers/cpufreq/Makefile
> +++ b/drivers/cpufreq/Makefile
> @@ -13,6 +13,8 @@ obj-$(CONFIG_CPU_FREQ_GOV_CONSERVATIVE)	+= cpufreq_conservative.o
>  # CPUfreq cross-arch helpers
>  obj-$(CONFIG_CPU_FREQ_TABLE)		+= freq_table.o
>  
> +obj-$(CONFIG_GENERIC_CPUFREQ_CPU0)	+= cpufreq-cpu0.o
> +
>  ##################################################################################
>  # x86 drivers.
>  # Link order matters. K8 is preferred to ACPI because of firmware bugs in early
> diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cpu0.c
> new file mode 100644
> index 0000000..f1bb7f37
> --- /dev/null
> +++ b/drivers/cpufreq/cpufreq-cpu0.c
> @@ -0,0 +1,235 @@
> +/*
> + * Copyright (C) 2012 Freescale Semiconductor, Inc.
> + *
> + * Reuse some codes from drivers/cpufreq/omap-cpufreq.c
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html
> + */
> +
> +#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
> +
> +#include <linux/clk.h>
> +#include <linux/cpu.h>
> +#include <linux/cpufreq.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/opp.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/slab.h>
> +
> +/* voltage tolerance in percentage */
> +static unsigned int voltage_tolerance;
> +
> +static struct device *cpu_dev;
> +static struct clk *cpu_clk;
> +static struct regulator *cpu_reg;
> +static struct cpufreq_frequency_table *freq_table;
> +
> +static int cpu0_verify_speed(struct cpufreq_policy *policy)
> +{
> +	return cpufreq_frequency_table_verify(policy, freq_table);
> +}
> +
> +static unsigned int cpu0_get_speed(unsigned int cpu)
> +{
> +	return clk_get_rate(cpu_clk) / 1000;
> +}
> +
> +static int cpu0_set_target(struct cpufreq_policy *policy,
> +			   unsigned int target_freq, unsigned int relation)
> +{
> +	struct cpufreq_freqs freqs;
> +	struct opp *opp;
> +	unsigned long freq_Hz, volt = 0, volt_old = 0, tol = 0;
> +	unsigned int index, cpu;
> +	int ret = 0;
> +
> +	ret = cpufreq_frequency_table_target(policy, freq_table, target_freq,
> +					     relation, &index);
> +	if (ret) {
> +		pr_err("failed to match target freqency %d: %d\n",
> +		       target_freq, ret);
> +		return ret;
> +	}
> +
> +	freq_Hz = clk_round_rate(cpu_clk, freq_table[index].frequency * 1000);
> +	if (freq_Hz < 0)
> +		freq_Hz = freq_table[index].frequency * 1000;
> +	freqs.new = freq_Hz / 1000;
> +	freqs.old = clk_get_rate(cpu_clk) / 1000;
> +
> +	if (freqs.old == freqs.new)
> +		return 0;
> +
> +	for_each_cpu(cpu, policy->cpus) {
> +		freqs.cpu = cpu;
> +		cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
> +	}
> +
> +	if (cpu_reg) {
> +		opp = opp_find_freq_ceil(cpu_dev, &freq_Hz);
> +		if (IS_ERR(opp)) {
> +			pr_err("failed to find OPP for %ld\n", freq_Hz);
> +			return PTR_ERR(opp);
> +		}
> +		volt = opp_get_voltage(opp);
> +		tol = volt * voltage_tolerance / 100;
> +		volt_old = regulator_get_voltage(cpu_reg);
> +	}
> +
> +	pr_debug("%u MHz, %ld mV --> %u MHz, %ld mV\n",
> +		 freqs.old / 1000, volt_old ? volt_old / 1000 : -1,
> +		 freqs.new / 1000, volt ? volt / 1000 : -1);
> +
> +	/* scaling up?  scale voltage before frequency */
> +	if (cpu_reg && freqs.new > freqs.old) {
> +		if (regulator_set_voltage(cpu_reg, volt - tol, volt + tol)) {
> +			pr_warn("Unable to scale voltage up\n");
> +			freqs.new = freqs.old;
> +			goto done;
> +		}
> +	}
> +
> +	ret = clk_set_rate(cpu_clk, freqs.new * 1000);
Check return value and fall back to previous point if it needs?
> +
> +	/* scaling down?  scale voltage after frequency */
> +	if (cpu_reg && (freqs.new < freqs.old)) {
> +		if (regulator_set_voltage(cpu_reg, volt - tol, volt + tol)) {
> +			pr_warn("Unable to scale voltage down\n");
> +			ret = clk_set_rate(cpu_clk, freqs.old * 1000);
> +			freqs.new = freqs.old;
> +			goto done;
> +		}
> +	}
> +
> +done:
> +	for_each_cpu(cpu, policy->cpus) {
> +		freqs.cpu = cpu;
> +		cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
> +	}
> +
> +	return ret;
> +}
> +
> +static int cpu0_cpufreq_init(struct cpufreq_policy *policy)
> +{
> +	struct device_node *np;
> +	int ret;
> +
> +	/* Initialize resources via CPU0 */
> +	if (policy->cpu != 0)
> +		return -EINVAL;
> +
> +	np = of_find_node_by_path("/cpus/cpu@0");
> +	if (!np) {
> +		pr_err("failed to find cpu0 node\n");
> +		return -ENOENT;
> +	}
> +
> +	cpu_dev = get_cpu_device(0);
> +	if (!cpu_dev) {
> +		pr_err("failed to get cpu0 device\n");
> +		ret = -ENODEV;
> +		goto out_put_node;
> +	}
> +
> +	cpu_dev->of_node = np;
hmm.. sys dev can not set of_node when populate it?
And why not do it in module init? 
> +	ret = of_init_opp_table(cpu_dev);
> +	if (ret) {
> +		pr_err("failed to init OPP table\n");
> +		goto out_put_node;
> +	}
> +
> +	ret = opp_init_cpufreq_table(cpu_dev, &freq_table);
> +	if (ret) {
> +		pr_err("failed to init cpufreq table\n");
> +		goto out_put_node;
> +	}
> +
> +	ret = cpufreq_frequency_table_cpuinfo(policy, freq_table);
> +	if (ret) {
> +		pr_err("invalid frequency table for cpu0\n");
> +		goto out_free_table;
> +	}
> +
> +	if (of_property_read_u32(np, "transition-latency",
> +				 &policy->cpuinfo.transition_latency))
> +		policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
> +
> +	of_property_read_u32(np, "voltage-tolerance", &voltage_tolerance);
> +
> +	cpu_clk = clk_get(cpu_dev, NULL);
> +	if (IS_ERR(cpu_clk)) {
> +		pr_err("failed to get cpu0 clock\n");
> +		ret = PTR_ERR(cpu_clk);
> +		goto out_free_table;
> +	}
> +	policy->cur = clk_get_rate(cpu_clk) / 1000;
> +
> +	cpu_reg = regulator_get(cpu_dev, "cpu0");
> +	if (IS_ERR(cpu_reg)) {
> +		pr_warn("failed to get cpu0 regulator\n");
> +		cpu_reg = NULL;
> +	}
> +
> +	/*
> +	 * The driver only supports the SMP configuartion where all processors
> +	 * share the clock and voltage and clock.  Use cpufreq affected_cpus
> +	 * interface to have all CPUs scaled together.
> +	 */
> +	policy->shared_type = CPUFREQ_SHARED_TYPE_ANY;
> +	cpumask_setall(policy->cpus);
> +
> +	cpufreq_frequency_table_get_attr(freq_table, policy->cpu);
> +
> +	of_node_put(np);
> +	return 0;
> +
> +out_free_table:
> +	opp_free_cpufreq_table(cpu_dev, &freq_table);
> +out_put_node:
> +	of_node_put(np);
> +	return ret;
> +}
> +
> +static int cpu0_cpufreq_exit(struct cpufreq_policy *policy)
> +{
> +	cpufreq_frequency_table_put_attr(policy->cpu);
> +	regulator_put(cpu_reg);
> +	clk_put(cpu_clk);
> +	opp_free_cpufreq_table(cpu_dev, &freq_table);
> +
> +	return 0;
> +}
> +
> +static struct freq_attr *cpu0_cpufreq_attr[] = {
> +	&cpufreq_freq_attr_scaling_available_freqs,
> +	NULL,
> +};
> +
> +static struct cpufreq_driver cpu0_cpufreq_driver = {
> +	.flags = CPUFREQ_STICKY,
> +	.verify = cpu0_verify_speed,
> +	.target = cpu0_set_target,
> +	.get = cpu0_get_speed,
> +	.init = cpu0_cpufreq_init,
> +	.exit = cpu0_cpufreq_exit,
> +	.name = "generic_cpu0",
> +	.attr = cpu0_cpufreq_attr,
> +};
static u32 max_freq = UINT_MAX / 1000; /* kHz */
module_param(max_freq, uint, 0);
MODULE_PARM_DESC(max_freq, "max cpu frequency in unit of kHz");

It's for debug. Make sense?

Thanks
Richard
> +
> +static int __devinit cpu0_cpufreq_driver_init(void)
> +{
> +	return cpufreq_register_driver(&cpu0_cpufreq_driver);
> +}
> +late_initcall(cpu0_cpufreq_driver_init);
> +
> +MODULE_AUTHOR("Shawn Guo <shawn.guo@linaro.org>");
> +MODULE_DESCRIPTION("Generic cpufreq driver for CPU0");
> +MODULE_LICENSE("GPL");
> -- 
> 1.7.5.4
>