On Fri, Dec 16, 2011 at 10:52:29AM +0000, Jamie Iles wrote:

Hi Richard,

A couple of questions inline, but otherwise looks nice!

Thanks for your review.

Jamie

On Fri, Dec 16, 2011 at 06:30:59PM +0800, Richard Zhao wrote:

quoted

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 <redacted>
---

[...]

quoted

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!!!

As I know, most share the same clk/volt. From the code:
IMX6: yes
Tegra: Yes, but strange it sets CPUFREQ_SHARED_TYPE_ALL.

MSM is an exception. I can support the case, but I have to make sure it's
handy to use.

quoted

+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?

ok. Thanks.

quoted

+		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]);

I forgot to delete this line.

quoted

+	freqs.new = freq_Hz / 1000;

Why round the rate then overwrite it?  Should this be freqs.new /= 1000?

quoted

+	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.

If we make recalculating smp loops_per_jiffy portable, this driver will
be portable too.

quoted

+};
+
+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!

The cpu clock should already be prepared/enabled. The same to the regulator.
IMHO, cpufreq is not used to handle cpu clk/power gating. The gating should be
handled by cpu hotplug, idle and suspend/resume.
Please correct me if I'm wrong.

quoted

+
+	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.

Good point. But would it be better to check cpu node compatible property?

Thanks
Richard

quoted

+
+MODULE_AUTHOR("Freescale Semiconductor Inc. Richard Zhao [off-list ref]");
+MODULE_DESCRIPTION("ARM SoC generic CPUFreq driver");
+MODULE_LICENSE("GPL");
-- 
1.7.5.4



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