[PATCH v3 3/3] cpufreq: Add a generic cpufreq-cpu0 driver
Rafael J. Wysocki
rjw at sisk.pl
Tue Sep 4 19:18:38 EDT 2012
On Friday, August 10, 2012, 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 at linaro.org>
I seem to recall that this has been discussed with several people and
undergone some changes as a result of comments. Would it be possible
to get some ACKs from the people involved?
> ---
> .../devicetree/bindings/cpufreq/cpufreq-cpu0.txt | 55 ++++
> drivers/cpufreq/Kconfig | 11 +
> drivers/cpufreq/Makefile | 2 +
> drivers/cpufreq/cpufreq-cpu0.c | 271 ++++++++++++++++++++
> 4 files changed, 339 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..4416ccc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
> @@ -0,0 +1,55 @@
> +Generic CPU0 cpufreq driver
> +
> +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 at 0.
> +
> +Required properties:
> +- operating-points: Refer to Documentation/devicetree/bindings/power/opp.txt
> + for details
> +
> +Optional properties:
> +- clock-latency: Specify the possible maximum transition latency for clock,
> + in unit of nanoseconds.
> +- voltage-tolerance: Specify the CPU voltage tolerance in percentage.
> +
> +Examples:
> +
> +cpus {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + cpu at 0 {
> + compatible = "arm,cortex-a9";
> + reg = <0>;
> + next-level-cache = <&L2>;
> + operating-points = <
> + /* kHz uV */
> + 792000 1100000
> + 396000 950000
> + 198000 850000
> + >;
> + transition-latency = <61036>; /* two CLK32 periods */
> + };
> +
> + cpu at 1 {
> + compatible = "arm,cortex-a9";
> + reg = <1>;
> + next-level-cache = <&L2>;
> + };
> +
> + cpu at 2 {
> + compatible = "arm,cortex-a9";
> + reg = <2>;
> + next-level-cache = <&L2>;
> + };
> +
> + cpu at 3 {
> + compatible = "arm,cortex-a9";
> + reg = <3>;
> + next-level-cache = <&L2>;
> + };
> +};
> diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> index e24a2a1..ea512f4 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 CPU0 cpufreq driver"
> + 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..fd3bac6
> --- /dev/null
> +++ b/drivers/cpufreq/cpufreq-cpu0.c
> @@ -0,0 +1,271 @@
> +/*
> + * Copyright (C) 2012 Freescale Semiconductor, Inc.
> + *
> + * Reuse some codes from drivers/cpufreq/omap-cpufreq.c
What do you mean by "reuse" here?
> + *
> + * 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:
The kernel is just GPLv2 (not later) and it will stay this way. Please
update this comment accordingly.
> + *
> + * 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>
> +
> +static unsigned int transition_latency;
> +static unsigned int voltage_tolerance; /* in percentage */
> +
> +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;
> +
> + 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_online_cpu(cpu) {
> + 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) {
> + ret = regulator_set_voltage_tol(cpu_reg, volt, tol);
> + if (ret) {
> + pr_err("failed to scale voltage up: %d\n", ret);
> + freqs.new = freqs.old;
> + return ret;
> + }
> + }
> +
> + ret = clk_set_rate(cpu_clk, freqs.new * 1000);
> + if (ret) {
> + pr_err("failed to set clock rate: %d\n", ret);
> + if (cpu_reg)
> + regulator_set_voltage_tol(cpu_reg, volt_old, tol);
> + return ret;
> + }
> +
> + /* scaling down? scale voltage after frequency */
> + if (cpu_reg && freqs.new < freqs.old) {
> + ret = regulator_set_voltage_tol(cpu_reg, volt, tol);
> + if (ret) {
> + pr_err("failed to scale voltage down: %d\n", ret);
> + clk_set_rate(cpu_clk, freqs.old * 1000);
> + freqs.new = freqs.old;
> + return ret;
> + }
> + }
> +
> + for_each_online_cpu(cpu) {
> + freqs.cpu = cpu;
> + cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
> + }
> +
> + return 0;
> +}
> +
> +static int cpu0_cpufreq_init(struct cpufreq_policy *policy)
> +{
> + int ret;
> +
> + if (policy->cpu != 0)
> + return -EINVAL;
> +
> + ret = cpufreq_frequency_table_cpuinfo(policy, freq_table);
> + if (ret) {
> + pr_err("invalid frequency table: %d\n", ret);
> + return ret;
> + }
> +
> + policy->cpuinfo.transition_latency = transition_latency;
> + policy->cur = clk_get_rate(cpu_clk) / 1000;
> +
> + /*
> + * 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);
> +
> + return 0;
> +}
> +
> +static int cpu0_cpufreq_exit(struct cpufreq_policy *policy)
> +{
> + cpufreq_frequency_table_put_attr(policy->cpu);
> +
> + 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 int __devinit cpu0_cpufreq_driver_init(void)
> +{
> + struct device_node *np;
> + int ret;
> +
> + np = of_find_node_by_path("/cpus/cpu at 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;
> +
> + cpu_clk = clk_get(cpu_dev, NULL);
> + if (IS_ERR(cpu_clk)) {
> + ret = PTR_ERR(cpu_clk);
> + pr_err("failed to get cpu0 clock: %d\n", ret);
> + goto out_put_node;
> + }
> +
> + cpu_reg = regulator_get(cpu_dev, "cpu0");
> + if (IS_ERR(cpu_reg)) {
> + pr_warn("failed to get cpu0 regulator\n");
> + cpu_reg = NULL;
> + }
> +
> + ret = of_init_opp_table(cpu_dev);
> + if (ret) {
> + pr_err("failed to init OPP table: %d\n", ret);
> + goto out_put_node;
> + }
> +
> + ret = opp_init_cpufreq_table(cpu_dev, &freq_table);
> + if (ret) {
> + pr_err("failed to init cpufreq table: %d\n", ret);
> + goto out_put_node;
> + }
> +
> + of_property_read_u32(np, "voltage-tolerance", &voltage_tolerance);
> +
> + if (of_property_read_u32(np, "clock-latency", &transition_latency))
> + transition_latency = CPUFREQ_ETERNAL;
> +
> + if (cpu_reg) {
> + struct opp *opp;
> + unsigned long min_uV, max_uV;
> + int i;
> +
> + /*
> + * OPP is maintained in order of increasing frequency, and
> + * freq_table initialised from OPP is therefore sorted in the
> + * same order.
> + */
> + for (i = 0; freq_table[i].frequency != CPUFREQ_TABLE_END; i++)
> + ;
> + opp = opp_find_freq_exact(cpu_dev,
> + freq_table[0].frequency * 1000, true);
> + min_uV = opp_get_voltage(opp);
> + opp = opp_find_freq_exact(cpu_dev,
> + freq_table[i-1].frequency * 1000, true);
> + max_uV = opp_get_voltage(opp);
> + ret = regulator_set_voltage_time(cpu_reg, min_uV, max_uV);
> + if (ret > 0)
> + transition_latency += ret * 1000;
> + }
> +
> + ret = cpufreq_register_driver(&cpu0_cpufreq_driver);
> + if (ret) {
> + pr_err("failed register driver: %d\n", ret);
> + goto out_free_table;
> + }
> +
> + 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;
> +}
> +late_initcall(cpu0_cpufreq_driver_init);
> +
> +MODULE_AUTHOR("Shawn Guo <shawn.guo at linaro.org>");
> +MODULE_DESCRIPTION("Generic CPU0 cpufreq driver");
> +MODULE_LICENSE("GPL");
Thanks,
Rafael
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