[RFC PATCH 2/6] cpufreq: cpufreq-cpu0: use clk rate-change notifiers

[Nishanth Menon]

From: Mike Turquette <mturquette@xxxxxxxxxx>

Removes directly handling of OPP tables and voltage regulators by
calling of_clk_cpufreq_notifier_handler, introduced by commit "clk:
cpufreq helper for voltage scaling".

In the future this can help consolidate code found across similar
CPUfreq drivers.

[nm@xxxxxx: updates to keep the OPP logic still in cpufreq-cpu0 -
optimization to generalize that for cpufreq is to be done in a later
series]
Signed-off-by: Nishanth Menon <nm@xxxxxx>
Signed-off-by: Mike Turquette <mturquette@xxxxxxxxxx>
---
 drivers/cpufreq/Kconfig        |    1 +
 drivers/cpufreq/cpufreq-cpu0.c |  140 ++++++++++++----------------------------
 2 files changed, 42 insertions(+), 99 deletions(-)

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 4b029c0..70b07ab 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -187,6 +187,7 @@ config GENERIC_CPUFREQ_CPU0
 	tristate "Generic CPU0 cpufreq driver"
 	depends on HAVE_CLK && REGULATOR && OF && THERMAL && CPU_THERMAL
 	select PM_OPP
+	select VOLTAGE_DOMAIN
 	help
 	  This adds a generic cpufreq driver for CPU0 frequency management.
 	  It supports both uniprocessor (UP) and symmetric multiprocessor (SMP)
diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cpu0.c
index 0c12ffc..32719d3 100644
--- a/drivers/cpufreq/cpufreq-cpu0.c
+++ b/drivers/cpufreq/cpufreq-cpu0.c
@@ -21,23 +21,20 @@
 #include <linux/of.h>
 #include <linux/pm_opp.h>
 #include <linux/platform_device.h>
-#include <linux/regulator/consumer.h>
+#include <linux/pm_voltage_domain.h>
 #include <linux/slab.h>
 #include <linux/thermal.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 struct thermal_cooling_device *cdev;
+static struct notifier_block *clk_nb;
 
 static int cpu0_set_target(struct cpufreq_policy *policy, unsigned int index)
 {
-	struct dev_pm_opp *opp;
-	unsigned long volt = 0, volt_old = 0, tol = 0;
 	unsigned int old_freq, new_freq;
 	long freq_Hz, freq_exact;
 	int ret;
@@ -50,50 +47,14 @@ static int cpu0_set_target(struct cpufreq_policy *policy, unsigned int index)
 	new_freq = freq_Hz / 1000;
 	old_freq = clk_get_rate(cpu_clk) / 1000;
 
-	if (!IS_ERR(cpu_reg)) {
-		rcu_read_lock();
-		opp = dev_pm_opp_find_freq_ceil(cpu_dev, &freq_Hz);
-		if (IS_ERR(opp)) {
-			rcu_read_unlock();
-			pr_err("failed to find OPP for %ld\n", freq_Hz);
-			return PTR_ERR(opp);
-		}
-		volt = dev_pm_opp_get_voltage(opp);
-		rcu_read_unlock();
-		tol = volt * voltage_tolerance / 100;
-		volt_old = regulator_get_voltage(cpu_reg);
-	}
-
-	pr_debug("%u MHz, %ld mV --> %u MHz, %ld mV\n",
-		 old_freq / 1000, volt_old ? volt_old / 1000 : -1,
-		 new_freq / 1000, volt ? volt / 1000 : -1);
-
-	/* scaling up?  scale voltage before frequency */
-	if (!IS_ERR(cpu_reg) && new_freq > old_freq) {
-		ret = regulator_set_voltage_tol(cpu_reg, volt, tol);
-		if (ret) {
-			pr_err("failed to scale voltage up: %d\n", ret);
-			return ret;
-		}
-	}
+	pr_debug("%u MHz --> %u MHz\n", old_freq / 1000, new_freq / 1000);
 
 	ret = clk_set_rate(cpu_clk, freq_exact);
 	if (ret) {
 		pr_err("failed to set clock rate: %d\n", ret);
-		if (!IS_ERR(cpu_reg))
-			regulator_set_voltage_tol(cpu_reg, volt_old, tol);
 		return ret;
 	}
 
-	/* scaling down?  scale voltage after frequency */
-	if (!IS_ERR(cpu_reg) && new_freq < old_freq) {
-		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, old_freq * 1000);
-		}
-	}
-
 	return ret;
 }
 
@@ -117,33 +78,24 @@ static struct cpufreq_driver cpu0_cpufreq_driver = {
 static int cpu0_cpufreq_probe(struct platform_device *pdev)
 {
 	struct device_node *np;
+	unsigned int voltage_latency;
 	int ret;
 
-	cpu_dev = get_cpu_device(0);
 	if (!cpu_dev) {
-		pr_err("failed to get cpu0 device\n");
-		return -ENODEV;
-	}
-
-	np = of_node_get(cpu_dev->of_node);
-	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");
+			return -ENODEV;
+		}
 
-	cpu_reg = devm_regulator_get_optional(cpu_dev, "cpu0");
-	if (IS_ERR(cpu_reg)) {
-		/*
-		 * If cpu0 regulator supply node is present, but regulator is
-		 * not yet registered, we should try defering probe.
-		 */
-		if (PTR_ERR(cpu_reg) == -EPROBE_DEFER) {
-			dev_err(cpu_dev, "cpu0 regulator not ready, retry\n");
-			ret = -EPROBE_DEFER;
-			goto out_put_node;
+		np = of_node_get(cpu_dev->of_node);
+		ret = of_init_opp_table(cpu_dev);
+		if (ret) {
+			pr_err("failed to init OPP table: %d\n", ret);
+			return ret;
 		}
-		pr_warn("failed to get cpu0 regulator: %ld\n",
-			PTR_ERR(cpu_reg));
+	} else {
+		np = of_node_get(cpu_dev->of_node);
 	}
 
 	cpu_clk = devm_clk_get(cpu_dev, NULL);
@@ -153,11 +105,8 @@ static int cpu0_cpufreq_probe(struct platform_device *pdev)
 		goto out_put_node;
 	}
 
-	ret = of_init_opp_table(cpu_dev);
-	if (ret) {
-		pr_err("failed to init OPP table: %d\n", ret);
-		goto out_put_node;
-	}
+	if (of_property_read_u32(np, "clock-latency", &transition_latency))
+		transition_latency = CPUFREQ_ETERNAL;
 
 	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
 	if (ret) {
@@ -165,40 +114,30 @@ static int cpu0_cpufreq_probe(struct platform_device *pdev)
 		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 (!IS_ERR(cpu_reg)) {
-		struct dev_pm_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++)
-			;
-		rcu_read_lock();
-		opp = dev_pm_opp_find_freq_exact(cpu_dev,
-				freq_table[0].frequency * 1000, true);
-		min_uV = dev_pm_opp_get_voltage(opp);
-		opp = dev_pm_opp_find_freq_exact(cpu_dev,
-				freq_table[i-1].frequency * 1000, true);
-		max_uV = dev_pm_opp_get_voltage(opp);
-		rcu_read_unlock();
-		ret = regulator_set_voltage_time(cpu_reg, min_uV, max_uV);
-		if (ret > 0)
-			transition_latency += ret * 1000;
+	clk_nb = of_pm_voltdm_notifier_register(cpu_dev, np, cpu_clk, "cpu0",
+					       &voltage_latency);
+
+	if (IS_ERR(clk_nb)) {
+		ret = PTR_ERR(clk_nb);
+		/* defer probe if regulator is not yet registered */
+		if (ret == -EPROBE_DEFER) {
+			dev_err(cpu_dev,
+				"cpu0 clock notifier not ready, retry\n");
+		} else {
+			dev_err(cpu_dev,
+				"Failed to register cpu0 clock notifier: %d\n",
+				ret);
+		}
+		goto out_freq_table_free;
 	}
 
+	if (voltage_latency > 0)
+		transition_latency += voltage_latency;
+
 	ret = cpufreq_register_driver(&cpu0_cpufreq_driver);
 	if (ret) {
 		pr_err("failed register driver: %d\n", ret);
-		goto out_free_table;
+		goto out_notifier_unregister;
 	}
 
 	/*
@@ -215,7 +154,9 @@ static int cpu0_cpufreq_probe(struct platform_device *pdev)
 	of_node_put(np);
 	return 0;
 
-out_free_table:
+out_notifier_unregister:
+	of_pm_voltdm_notifier_unregister(clk_nb);
+out_freq_table_free:
 	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
 out_put_node:
 	of_node_put(np);
@@ -226,6 +167,7 @@ static int cpu0_cpufreq_remove(struct platform_device *pdev)
 {
 	cpufreq_cooling_unregister(cdev);
 	cpufreq_unregister_driver(&cpu0_cpufreq_driver);
+	of_pm_voltdm_notifier_unregister(clk_nb);
 	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
 
 	return 0;
-- 
1.7.9.5

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