[PATCH V2 1/4] cpufreq: add arm soc generic cpufreq driver
Jamie Iles
jamie at jamieiles.com
Fri Dec 16 05:52:29 EST 2011
Hi Richard,
A couple of questions inline, but otherwise looks nice!
Jamie
On Fri, Dec 16, 2011 at 06:30:59PM +0800, Richard Zhao wrote:
> It support single core and multi-core ARM SoCs. But it assume
> all cores share the same frequency and voltage.
>
> Signed-off-by: Richard Zhao <richard.zhao at linaro.org>
> ---
[...]
> diff --git a/drivers/cpufreq/arm-cpufreq.c b/drivers/cpufreq/arm-cpufreq.c
> new file mode 100644
> index 0000000..e4d20da
> --- /dev/null
> +++ b/drivers/cpufreq/arm-cpufreq.c
> @@ -0,0 +1,269 @@
> +/*
> + * Copyright (C) 2011 Freescale Semiconductor, Inc.
> + */
> +
> +/*
> + * 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
> + */
> +
> +#include <linux/module.h>
> +#include <linux/cpufreq.h>
> +#include <linux/clk.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/err.h>
> +#include <linux/slab.h>
> +#include <linux/of.h>
> +#include <asm/cpu.h>
> +
> +static u32 *cpu_freqs; /* HZ */
> +static u32 *cpu_volts; /* uV */
> +static u32 trans_latency; /* ns */
> +static int cpu_op_nr;
> +
> +static DEFINE_PER_CPU(unsigned long, l_p_j_ref);
> +static unsigned long l_p_j_ref_freq;
> +
> +static struct clk *cpu_clk;
This assumes that all CPU's share the same clk and run at the same rate.
Is that a fair/safe assumption? I honestly don't know the answer to
this so it's just a question!!!
> +static struct regulator *cpu_reg;
> +static struct cpufreq_frequency_table *arm_freq_table;
> +
> +static int set_cpu_freq(unsigned long freq, int index, int higher)
> +{
> + int ret = 0;
> +
> + if (higher && cpu_reg)
> + regulator_set_voltage(cpu_reg,
> + cpu_volts[index], cpu_volts[index]);
> +
> + ret = clk_set_rate(cpu_clk, freq);
> + if (ret != 0) {
> + printk(KERN_DEBUG "cannot set CPU clock rate\n");
Perhaps use pr_debug() and friends throughout this driver?
> + return ret;
> + }
> +
> + if (!higher && cpu_reg)
> + regulator_set_voltage(cpu_reg,
> + cpu_volts[index], cpu_volts[index]);
> +
> + return ret;
> +}
> +
> +static int arm_verify_speed(struct cpufreq_policy *policy)
> +{
> + return cpufreq_frequency_table_verify(policy, arm_freq_table);
> +}
> +
> +static unsigned int arm_get_speed(unsigned int cpu)
> +{
> + return clk_get_rate(cpu_clk) / 1000;
> +}
> +
> +static int arm_set_target(struct cpufreq_policy *policy,
> + unsigned int target_freq, unsigned int relation)
> +{
> + struct cpufreq_freqs freqs;
> + unsigned long freq_Hz;
> + int cpu;
> + int ret = 0;
> + unsigned int index;
> +
> + cpufreq_frequency_table_target(policy, arm_freq_table,
> + target_freq, relation, &index);
> + freq_Hz = clk_round_rate(cpu_clk, cpu_freqs[index]);
> + freq_Hz = freq_Hz ? freq_Hz : cpu_freqs[index];
> + freqs.old = clk_get_rate(cpu_clk) / 1000;
> + freqs.new = clk_round_rate(cpu_clk, cpu_freqs[index]);
> + freqs.new = freq_Hz / 1000;
Why round the rate then overwrite it? Should this be freqs.new /= 1000?
> + freqs.flags = 0;
> +
> + if (freqs.old == freqs.new)
> + return 0;
> +
> + for_each_possible_cpu(cpu) {
> + freqs.cpu = cpu;
> + cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
> + }
> +
> + ret = set_cpu_freq(freq_Hz, index, (freqs.new > freqs.old));
> +
> +#ifdef CONFIG_SMP
> + /* loops_per_jiffy is not updated by the cpufreq core for SMP systems.
> + * So update it for all CPUs.
> + */
> + for_each_possible_cpu(cpu)
> + per_cpu(cpu_data, cpu).loops_per_jiffy =
> + cpufreq_scale(per_cpu(l_p_j_ref, cpu), l_p_j_ref_freq,
> + freqs.new);
> +#endif
> +
> + for_each_possible_cpu(cpu) {
> + freqs.cpu = cpu;
> + cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
> + }
> +
> + return ret;
> +}
> +
> +static int arm_cpufreq_init(struct cpufreq_policy *policy)
> +{
> + int ret;
> +
> + if (policy->cpu >= num_possible_cpus())
> + return -EINVAL;
> +
> + policy->cur = clk_get_rate(cpu_clk) / 1000;
> + policy->shared_type = CPUFREQ_SHARED_TYPE_ANY;
> + cpumask_setall(policy->cpus);
> + /* Manual states, that PLL stabilizes in two CLK32 periods */
> + policy->cpuinfo.transition_latency = trans_latency;
> +
> + ret = cpufreq_frequency_table_cpuinfo(policy, arm_freq_table);
> +
> + if (ret < 0) {
> + printk(KERN_ERR "%s: invalid frequency table for cpu %d\n",
> + __func__, policy->cpu);
> + return ret;
> + }
> +
> + cpufreq_frequency_table_get_attr(arm_freq_table, policy->cpu);
> + return 0;
> +}
> +
> +static int arm_cpufreq_exit(struct cpufreq_policy *policy)
> +{
> + cpufreq_frequency_table_put_attr(policy->cpu);
> + return 0;
> +}
> +
> +static struct cpufreq_driver arm_cpufreq_driver = {
> + .flags = CPUFREQ_STICKY,
> + .verify = arm_verify_speed,
> + .target = arm_set_target,
> + .get = arm_get_speed,
> + .init = arm_cpufreq_init,
> + .exit = arm_cpufreq_exit,
> + .name = "arm",
Is this really just for ARM or can it be a generic-clk driver? I can't
see any ARM specifics here.
> +};
> +
> +static int __devinit arm_cpufreq_driver_init(void)
> +{
> + struct device_node *cpu0;
> + const struct property *pp;
> + int cpu, i, ret;
> +
> + printk(KERN_INFO "ARM SoC generic CPU frequency driver\n");
> +
> + cpu0 = of_find_node_by_path("/cpus/cpu at 0");
> + if (!cpu0)
> + return -ENODEV;
> +
> + pp = of_find_property(cpu0, "cpu-freqs", NULL);
> + if (!pp) {
> + ret = -ENODEV;
> + goto put_node;
> + }
> + cpu_op_nr = pp->length / sizeof(u32);
> + if (!cpu_op_nr) {
> + ret = -ENODEV;
> + goto put_node;
> + }
> + ret = -ENOMEM;
> + cpu_freqs = kzalloc(sizeof(*cpu_freqs) * cpu_op_nr, GFP_KERNEL);
> + if (!cpu_freqs)
> + goto put_node;
> + of_property_read_u32_array(cpu0, "cpu-freqs", cpu_freqs, cpu_op_nr);
> +
> + pp = of_find_property(cpu0, "cpu-volts", NULL);
> + if (pp) {
> + if (cpu_op_nr == pp->length / sizeof(u32)) {
> + cpu_volts = kzalloc(sizeof(*cpu_freqs) * cpu_op_nr,
> + GFP_KERNEL);
> + if (!cpu_volts)
> + goto free_cpu_freqs;
> + of_property_read_u32_array(cpu0, "cpu-volts",
> + cpu_volts, cpu_op_nr);
> + } else
> + printk(KERN_WARNING "cpufreq: invalid cpu_volts!\n");
> + }
> +
> + if (of_property_read_u32(cpu0, "trans-latency", &trans_latency))
> + trans_latency = CPUFREQ_ETERNAL;
> +
> + arm_freq_table = kmalloc(sizeof(struct cpufreq_frequency_table)
> + * (cpu_op_nr + 1), GFP_KERNEL);
> + if (!arm_freq_table)
> + goto free_cpu_volts;
> +
> + for (i = 0; i < cpu_op_nr; i++) {
> + arm_freq_table[i].index = i;
> + arm_freq_table[i].frequency = cpu_freqs[i] / 1000;
> + }
> +
> + arm_freq_table[i].index = i;
> + arm_freq_table[i].frequency = CPUFREQ_TABLE_END;
> +
> + cpu_clk = clk_get(NULL, "cpu");
> + if (IS_ERR(cpu_clk)) {
> + printk(KERN_ERR "%s: failed to get cpu clock\n", __func__);
> + ret = PTR_ERR(cpu_clk);
> + goto free_freq_table;
> + }
Should there be a clk_prepare() + clk_enable() pair here? I can't see
it would really be needed but maybe for completeness? Again, just a
question!
> +
> + if (cpu_volts) {
> + cpu_reg = regulator_get(NULL, "cpu");
> + if (IS_ERR(cpu_reg)) {
> + printk(KERN_WARNING
> + "cpufreq: regulator cpu get failed.\n");
> + cpu_reg = NULL;
> + }
> + }
> +
> + l_p_j_ref_freq = clk_get_rate(cpu_clk);
> + for_each_possible_cpu(cpu)
> + per_cpu(l_p_j_ref, cpu) =
> + per_cpu(cpu_data, cpu).loops_per_jiffy;
> +
> + ret = cpufreq_register_driver(&arm_cpufreq_driver);
> + if (ret)
> + goto reg_put;
> +
> + of_node_put(cpu0);
> +
> + return 0;
> +
> +reg_put:
> + if (cpu_reg)
> + regulator_put(cpu_reg);
> + clk_put(cpu_clk);
> +free_freq_table:
> + kfree(arm_freq_table);
> +free_cpu_volts:
> + kfree(cpu_volts);
> +free_cpu_freqs:
> + kfree(cpu_freqs);
> +put_node:
> + of_node_put(cpu0);
> +
> + return ret;
> +}
> +
> +static void arm_cpufreq_driver_exit(void)
> +{
> + cpufreq_unregister_driver(&arm_cpufreq_driver);
> + kfree(cpu_freqs);
> + kfree(cpu_volts);
> + kfree(arm_freq_table);
> + clk_put(cpu_clk);
> +}
> +
> +module_init(arm_cpufreq_driver_init);
> +module_exit(arm_cpufreq_driver_exit);
Are there any ARM platforms that wouldn't be able to use this driver?
If there are then should platforms "opt-in" by calling a register
function rather than having it auto registering as when we have multiple
platforms in a single zImage the probe errors might not be too nice.
> +
> +MODULE_AUTHOR("Freescale Semiconductor Inc. Richard Zhao <richard.zhao at freescale.com>");
> +MODULE_DESCRIPTION("ARM SoC generic CPUFreq driver");
> +MODULE_LICENSE("GPL");
> --
> 1.7.5.4
>
>
>
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