cpufreq: OMAP: scale voltage along with frequency

Use the regulator framework to get the voltage regulator associated
with the MPU voltage domain and use it to scale voltage along with
frequency.

While here, CONFIG_CPU_FREQ_DEBUG doesn't exist anymore, so move
debug prints to use dev_dbg().

Special thanks to Afzal Mohammed for suggestions on more robust error
checking.

Cc: Afzal Mohammed  <afzal@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>

drivers/cpufreq/omap-cpufreq.c

@@ -25,6 +25,7 @@
 #include <linux/opp.h>
 #include <linux/cpu.h>
 #include <linux/module.h>
+#include <linux/regulator/consumer.h>
 
 #include <asm/system.h>
 #include <asm/smp_plat.h>
@@ -52,6 +53,7 @@ static atomic_t freq_table_users = ATOMIC_INIT(0);
 static struct clk *mpu_clk;
 static char *mpu_clk_name;
 static struct device *mpu_dev;
+static struct regulator *mpu_reg;
 
 static int omap_verify_speed(struct cpufreq_policy *policy)
 {
@@ -76,8 +78,10 @@ static int omap_target(struct cpufreq_policy *policy,
 		       unsigned int relation)
 {
 	unsigned int i;
-	int ret = 0;
+	int r, ret = 0;
 	struct cpufreq_freqs freqs;
+	struct opp *opp;
+	unsigned long freq, volt = 0, volt_old = 0;
 
 	if (!freq_table) {
 		dev_err(mpu_dev, "%s: cpu%d: no freq table!\n", __func__,
@@ -111,13 +115,49 @@ static int omap_target(struct cpufreq_policy *policy,
 		cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
 	}
 
-#ifdef CONFIG_CPU_FREQ_DEBUG
-	pr_info("cpufreq-omap: transition: %u --> %u\n", freqs.old, freqs.new);
-#endif
+	freq = freqs.new * 1000;
+
+	if (mpu_reg) {
+		opp = opp_find_freq_ceil(mpu_dev, &freq);
+		if (IS_ERR(opp)) {
+			dev_err(mpu_dev, "%s: unable to find MPU OPP for %d\n",
+				__func__, freqs.new);
+			return -EINVAL;
+		}
+		volt = opp_get_voltage(opp);
+		volt_old = regulator_get_voltage(mpu_reg);
+	}
+
+	dev_dbg(mpu_dev, "cpufreq-omap: %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 (mpu_reg && (freqs.new > freqs.old)) {
+		r = regulator_set_voltage(mpu_reg, volt, volt);
+		if (r < 0) {
+			dev_warn(mpu_dev, "%s: unable to scale voltage up.\n",
+				 __func__);
+			freqs.new = freqs.old;
+			goto done;
+		}
+	}
 
 	ret = clk_set_rate(mpu_clk, freqs.new * 1000);
-	freqs.new = omap_getspeed(policy->cpu);
 
+	/* scaling down?  scale voltage after frequency */
+	if (mpu_reg && (freqs.new < freqs.old)) {
+		r = regulator_set_voltage(mpu_reg, volt, volt);
+		if (r < 0) {
+			dev_warn(mpu_dev, "%s: unable to scale voltage down.\n",
+				 __func__);
+			ret = clk_set_rate(mpu_clk, freqs.old * 1000);
+			freqs.new = freqs.old;
+			goto done;
+		}
+	}
+
+	freqs.new = omap_getspeed(policy->cpu);
 #ifdef CONFIG_SMP
 	/*
 	 * Note that loops_per_jiffy is not updated on SMP systems in
@@ -144,6 +184,7 @@ static int omap_target(struct cpufreq_policy *policy,
 					freqs.new);
 #endif
 
+done:
 	/* notifiers */
 	for_each_cpu(i, policy->cpus) {
 		freqs.cpu = i;
@@ -260,6 +301,23 @@ static int __init omap_cpufreq_init(void)
 		return -EINVAL;
 	}
 
+	mpu_reg = regulator_get(mpu_dev, "vcc");
+	if (IS_ERR(mpu_reg)) {
+		pr_warning("%s: unable to get MPU regulator\n", __func__);
+		mpu_reg = NULL;
+	} else {
+		/* 
+		 * Ensure physical regulator is present.
+		 * (e.g. could be dummy regulator.)
+		 */
+		if (regulator_get_voltage(mpu_reg) < 0) {
+			pr_warn("%s: physical regulator not present for MPU\n",
+				__func__);
+			regulator_put(mpu_reg);
+			mpu_reg = NULL;
+		}
+	}
+
 	return cpufreq_register_driver(&omap_driver);
 }