Subject: [PATCH V3 4/7] cpufreq: add generic cpufreq driver

From: [email-masked] (Richard Zhao)
Date: Mon, 19 Dec 2011 22:19:29 +0800

On Mon, Dec 19, 2011 at 10:05:12AM +0000, Jamie Iles wrote:
> Hi Richard,
> 
> On Mon, Dec 19, 2011 at 11:21:40AM +0800, Richard Zhao wrote:
> > It support single core and multi-core ARM SoCs. But currently it assume
> > all cores share the same frequency and voltage.
> > 
> > Signed-off-by: Richard Zhao <[email-masked]>
> > ---
> >  .../devicetree/bindings/cpufreq/generic-cpufreq    |    7 +
> >  drivers/cpufreq/Kconfig                            |    8 +
> >  drivers/cpufreq/Makefile                           |    2 +
> >  drivers/cpufreq/generic-cpufreq.c                  |  251 ++++++++++++++++++++
> >  4 files changed, 268 insertions(+), 0 deletions(-)
> >  create mode 100644 Documentation/devicetree/bindings/cpufreq/generic-cpufreq
> >  create mode 100644 drivers/cpufreq/generic-cpufreq.c
> > 
> > diff --git a/Documentation/devicetree/bindings/cpufreq/generic-cpufreq b/Documentation/devicetree/bindings/cpufreq/generic-cpufreq
> > new file mode 100644
> > index 0000000..15dd780
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/cpufreq/generic-cpufreq
> > @@ -0,0 +1,7 @@
> > +Generic cpufreq driver
> > +
> > +Required properties in /cpus/cpu at 0:
> > +- compatible : "generic-cpufreq"
> 
> I'm not convinced this is the best way to do this.  By requiring a 
> generic-cpufreq compatible string we're encoding Linux driver 
> information into the hardware description.  The only way I can see to 
> avoid this is to provide a generic_clk_cpufreq_init() function that 
> platforms can call in their machine init code to use the driver.
It'll prevent the driver from being a kernel module.

Hi Grant & Rob,

Could you comment?

> 
> > +- cpu-freqs : cpu frequency points it support
> > +- cpu-volts : cpu voltages required by the frequency point at the same index
> > +- trans-latency :  transition_latency
> > diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> > index e24a2a1..216eecd 100644
> > --- a/drivers/cpufreq/Kconfig
> > +++ b/drivers/cpufreq/Kconfig
> > @@ -179,6 +179,14 @@ config CPU_FREQ_GOV_CONSERVATIVE
> >  
> >  	  If in doubt, say N.
> >  
> > +config GENERIC_CPUFREQ_DRIVER
> > +	bool "Generic cpufreq driver using clock/regulator/devicetree"
> > +	help
> > +	  This adds generic CPUFreq driver. It assumes all
> > +	  cores of the CPU share the same clock and voltage.
> > +
> > +	  If in doubt, say N.
> 
> I think this needs dependencies on HAVE_CLK, OF and REGULATOR.
right, Thanks. I can not check clk before generic clock framework
come in.
Added:
	depends on OF && REGULATOR
	select CPU_FREQ_TABLE
> 
> > +
> >  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 ce75fcb..2dbdab1 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_DRIVER)	+= generic-cpufreq.o
> > +
> >  ##################################################################################
> >  # x86 drivers.
> >  # Link order matters. K8 is preferred to ACPI because of firmware bugs in early
> > diff --git a/drivers/cpufreq/generic-cpufreq.c b/drivers/cpufreq/generic-cpufreq.c
> > new file mode 100644
> > index 0000000..781bb9b
> > --- /dev/null
> > +++ b/drivers/cpufreq/generic-cpufreq.c
> > @@ -0,0 +1,251 @@
> > +/*
> > + * 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>
> > +
> > +static u32 *cpu_freqs; /* HZ */
> > +static u32 *cpu_volts; /* uV */
> > +static u32 trans_latency; /* ns */
> > +static int cpu_op_nr;
> > +
> > +static struct clk *cpu_clk;
> > +static struct regulator *cpu_reg;
> > +static struct cpufreq_frequency_table *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) {
> > +		pr_err("generic-cpufreq: cannot set CPU clock rate\n");
> > +		return ret;
> > +	}
> > +
> > +	if (!higher && cpu_reg)
> > +		regulator_set_voltage(cpu_reg,
> > +				cpu_volts[index], cpu_volts[index]);
> > +
> > +	return ret;
> > +}
> > +
> > +static int generic_verify_speed(struct cpufreq_policy *policy)
> > +{
> > +	return cpufreq_frequency_table_verify(policy, freq_table);
> > +}
> > +
> > +static unsigned int generic_get_speed(unsigned int cpu)
> > +{
> > +	return clk_get_rate(cpu_clk) / 1000;
> > +}
> > +
> > +static int generic_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, 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 = freq_Hz / 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));
> 
> If this fails then we'll still be notifying the transition at the 
> requested rate even though it didn't work.  I guess we should really get 
> the rate of the clk and put that into freqs for the POSTCHANGE 
> notification.
right, Thanks.
Added:
	if (ret)
		freq.new = clk_get_rate(cpu_clk) / 1000;

> 
> > +
> > +	for_each_possible_cpu(cpu) {
> > +		freqs.cpu = cpu;
> > +		cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static int generic_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, freq_table);
> > +
> > +	if (ret < 0) {
> > +		pr_err("%s: invalid frequency table for cpu %d\n",
> > +		       __func__, policy->cpu);
> > +		return ret;
> > +	}
> > +
> > +	cpufreq_frequency_table_get_attr(freq_table, policy->cpu);
> > +	return 0;
> > +}
> > +
> > +static int generic_cpufreq_exit(struct cpufreq_policy *policy)
> > +{
> > +	cpufreq_frequency_table_put_attr(policy->cpu);
> > +	return 0;
> > +}
> > +
> > +static struct cpufreq_driver generic_cpufreq_driver = {
> > +	.flags = CPUFREQ_STICKY,
> > +	.verify = generic_verify_speed,
> > +	.target = generic_set_target,
> > +	.get = generic_get_speed,
> > +	.init = generic_cpufreq_init,
> > +	.exit = generic_cpufreq_exit,
> > +	.name = "generic",
> 
> This may be a little too generic?  "generic-reg-clk"?
I ever thought about it. If it's exact, it'll be "generic-reg-clk-dt".
Is "generic-reg-clk" or "generic-reg-clk-dt" too long for file name?
> 
> > +};
> > +
> > +static int __devinit generic_cpufreq_driver_init(void)
> > +{
> > +	struct device_node *cpu0;
> > +	const struct property *pp;
> > +	int i, ret;
> > +
> > +	pr_info("Generic CPU frequency driver\n");
> > +
> > +	cpu0 = of_find_node_by_path("/cpus/cpu at 0");
> > +	if (!cpu0)
> > +		return -ENODEV;
> > +
> > +	if (!of_device_is_compatible(cpu0, "generic-cpufreq"))
> > +		return -ENODEV;
> 
> As above, I'd personally rather not use compatible strings, 
I still think checking compatible is better. So I need device tree
maintainer's comments.
> but if you 
> do, then I think return 0 here rather than -ENODEV else I believe you'll 
> get a potentially confusing message on the console for platforms that 
> don't use this.
I should let it be tristate. If it's not compatible, I don't need
the module any more.
> 
> > +
> > +	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
> > +			pr_warn("%s: invalid cpu_volts!\n", __func__);
> > +	}
> > +
> > +	if (of_property_read_u32(cpu0, "trans-latency", &trans_latency))
> > +		trans_latency = CPUFREQ_ETERNAL;
> > +
> > +	freq_table = kmalloc(sizeof(struct cpufreq_frequency_table)
> > +				* (cpu_op_nr + 1), GFP_KERNEL);
> > +	if (!freq_table)
> > +		goto free_cpu_volts;
> > +
> > +	for (i = 0; i < cpu_op_nr; i++) {
> > +		freq_table[i].index = i;
> > +		freq_table[i].frequency = cpu_freqs[i] / 1000;
> > +	}
> > +
> > +	freq_table[i].index = i;
> > +	freq_table[i].frequency = CPUFREQ_TABLE_END;
> > +
> > +	cpu_clk = clk_get(NULL, "cpu");
> > +	if (IS_ERR(cpu_clk)) {
> > +		pr_err("%s: failed to get cpu clock\n", __func__);
> > +		ret = PTR_ERR(cpu_clk);
> > +		goto free_freq_table;
> > +	}
> > +
> > +	if (cpu_volts) {
> > +		cpu_reg = regulator_get(NULL, "cpu");
> > +		if (IS_ERR(cpu_reg)) {
> > +			pr_warn("%s: regulator cpu get failed.\n", __func__);
> > +			cpu_reg = NULL;
> > +		}
> > +	}
> > +
> > +	ret = cpufreq_register_driver(&generic_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(freq_table);
> > +free_cpu_volts:
> > +	kfree(cpu_volts);
> > +free_cpu_freqs:
> > +	kfree(cpu_freqs);
> > +put_node:
> > +	of_node_put(cpu0);
> > +
> > +	return ret;
> > +}
> > +
> > +static void generic_cpufreq_driver_exit(void)
> > +{
> > +	cpufreq_unregister_driver(&generic_cpufreq_driver);
> > +	kfree(cpu_freqs);
> > +	kfree(cpu_volts);
> > +	kfree(freq_table);
> > +	clk_put(cpu_clk);
> 
> Should this do something with the regulator too?
right.
Added:
	if (cpu_reg)
		regulator_put(cpu_reg);

Thanks very much for your review!
Richard
> Jamie