cpufreq: mediatek: Refine mtk_cpufreq_voltage_tracking()

Because the difference of sram and proc should in a range of min_volt_shift
and max_volt_shift. We need to adjust the sram and proc step by step.

We replace VOLT_TOL (voltage tolerance) with the platform data and update the
logic to determine the voltage boundary and invoking regulator_set_voltage.

- Use 'sram_min_volt' and 'sram_max_volt' to determine the voltage boundary
  of sram regulator.
- Use (sram_min_volt - min_volt_shift) and 'proc_max_volt' to determine the
  voltage boundary of vproc regulator.

Moreover, to prevent infinite loop when tracking voltage, we calculate the
maximum value for each platform data.
We assume min voltage is 0 and tracking target voltage using
min_volt_shift for each iteration.
The retry_max is 3 times of expeted iteration count.
Signed-off-by: Jia-Wei Chang <jia-wei.chang@mediatek.com>
Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/mediatek-cpufreq.c

@@ -8,6 +8,7 @@
 #include <linux/cpu.h>
 #include <linux/cpufreq.h>
 #include <linux/cpumask.h>
+#include <linux/minmax.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
@@ -15,8 +16,6 @@
 #include <linux/pm_opp.h>
 #include <linux/regulator/consumer.h>
 
-#define VOLT_TOL		(10000)
-
 struct mtk_cpufreq_platform_data {
 	int min_volt_shift;
 	int max_volt_shift;
@@ -48,6 +47,7 @@ struct mtk_cpu_dvfs_info {
 	bool need_voltage_tracking;
 	int pre_vproc;
 	const struct mtk_cpufreq_platform_data *soc_data;
+	int vtrack_max;
 };
 
 static struct platform_device *cpufreq_pdev;
@@ -73,6 +73,7 @@ static int mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
 	struct regulator *proc_reg = info->proc_reg;
 	struct regulator *sram_reg = info->sram_reg;
 	int pre_vproc, pre_vsram, new_vsram, vsram, vproc, ret;
+	int retry = info->vtrack_max;
 
 	pre_vproc = regulator_get_voltage(proc_reg);
 	if (pre_vproc < 0) {
@@ -80,91 +81,44 @@ static int mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
 			"invalid Vproc value: %d\n", pre_vproc);
 		return pre_vproc;
 	}
-	/* Vsram should not exceed the maximum allowed voltage of SoC. */
-	new_vsram = min(new_vproc + soc_data->min_volt_shift,
-			soc_data->sram_max_volt);
-
-	if (pre_vproc < new_vproc) {
-		/*
-		 * When scaling up voltages, Vsram and Vproc scale up step
-		 * by step. At each step, set Vsram to (Vproc + 200mV) first,
-		 * then set Vproc to (Vsram - 100mV).
-		 * Keep doing it until Vsram and Vproc hit target voltages.
-		 */
-		do {
-			pre_vsram = regulator_get_voltage(sram_reg);
-			if (pre_vsram < 0) {
-				dev_err(info->cpu_dev,
-					"invalid Vsram value: %d\n", pre_vsram);
-				return pre_vsram;
-			}
-			pre_vproc = regulator_get_voltage(proc_reg);
-			if (pre_vproc < 0) {
-				dev_err(info->cpu_dev,
-					"invalid Vproc value: %d\n", pre_vproc);
-				return pre_vproc;
-			}
-
-			vsram = min(new_vsram,
-				    pre_vproc + soc_data->min_volt_shift);
 
-			if (vsram + VOLT_TOL >= soc_data->sram_max_volt) {
-				vsram = soc_data->sram_max_volt;
+	pre_vsram = regulator_get_voltage(sram_reg);
+	if (pre_vsram < 0) {
+		dev_err(info->cpu_dev, "invalid Vsram value: %d\n", pre_vsram);
+		return pre_vsram;
+	}
 
-				/*
-				 * If the target Vsram hits the maximum voltage,
-				 * try to set the exact voltage value first.
-				 */
-				ret = regulator_set_voltage(sram_reg, vsram,
-							    vsram);
-				if (ret)
-					ret = regulator_set_voltage(sram_reg,
-							vsram - VOLT_TOL,
-							vsram);
+	new_vsram = clamp(new_vproc + soc_data->min_volt_shift,
+			  soc_data->sram_min_volt, soc_data->sram_max_volt);
 
-				vproc = new_vproc;
-			} else {
-				ret = regulator_set_voltage(sram_reg, vsram,
-							    vsram + VOLT_TOL);
+	do {
+		if (pre_vproc <= new_vproc) {
+			vsram = clamp(pre_vproc + soc_data->max_volt_shift,
+				      soc_data->sram_min_volt, new_vsram);
+			ret = regulator_set_voltage(sram_reg, vsram,
+						    soc_data->sram_max_volt);
 
-				vproc = vsram - soc_data->min_volt_shift;
-			}
 			if (ret)
 				return ret;
 
+			if (vsram == soc_data->sram_max_volt ||
+			    new_vsram == soc_data->sram_min_volt)
+				vproc = new_vproc;
+			else
+				vproc = vsram - soc_data->min_volt_shift;
+
 			ret = regulator_set_voltage(proc_reg, vproc,
-						    vproc + VOLT_TOL);
+						    soc_data->proc_max_volt);
 			if (ret) {
 				regulator_set_voltage(sram_reg, pre_vsram,
-						      pre_vsram);
+						      soc_data->sram_max_volt);
 				return ret;
 			}
-		} while (vproc < new_vproc || vsram < new_vsram);
-	} else if (pre_vproc > new_vproc) {
-		/*
-		 * When scaling down voltages, Vsram and Vproc scale down step
-		 * by step. At each step, set Vproc to (Vsram - 200mV) first,
-		 * then set Vproc to (Vproc + 100mV).
-		 * Keep doing it until Vsram and Vproc hit target voltages.
-		 */
-		do {
-			pre_vproc = regulator_get_voltage(proc_reg);
-			if (pre_vproc < 0) {
-				dev_err(info->cpu_dev,
-					"invalid Vproc value: %d\n", pre_vproc);
-				return pre_vproc;
-			}
-			pre_vsram = regulator_get_voltage(sram_reg);
-			if (pre_vsram < 0) {
-				dev_err(info->cpu_dev,
-					"invalid Vsram value: %d\n", pre_vsram);
-				return pre_vsram;
-			}
-
+		} else if (pre_vproc > new_vproc) {
 			vproc = max(new_vproc,
 				    pre_vsram - soc_data->max_volt_shift);
 			ret = regulator_set_voltage(proc_reg, vproc,
-						    vproc + VOLT_TOL);
+						    soc_data->proc_max_volt);
 			if (ret)
 				return ret;
 
@@ -174,32 +128,24 @@ static int mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
 				vsram = max(new_vsram,
 					    vproc + soc_data->min_volt_shift);
 
-			if (vsram + VOLT_TOL >= soc_data->sram_max_volt) {
-				vsram = soc_data->sram_max_volt;
-
-				/*
-				 * If the target Vsram hits the maximum voltage,
-				 * try to set the exact voltage value first.
-				 */
-				ret = regulator_set_voltage(sram_reg, vsram,
-							    vsram);
-				if (ret)
-					ret = regulator_set_voltage(sram_reg,
-							vsram - VOLT_TOL,
-							vsram);
-			} else {
-				ret = regulator_set_voltage(sram_reg, vsram,
-							    vsram + VOLT_TOL);
-			}
-
+			ret = regulator_set_voltage(sram_reg, vsram,
+						    soc_data->sram_max_volt);
 			if (ret) {
 				regulator_set_voltage(proc_reg, pre_vproc,
-						      pre_vproc);
+						      soc_data->proc_max_volt);
 				return ret;
 			}
-		} while (vproc > new_vproc + VOLT_TOL ||
-			 vsram > new_vsram + VOLT_TOL);
-	}
+		}
+
+		pre_vproc = vproc;
+		pre_vsram = vsram;
+
+		if (--retry < 0) {
+			dev_err(info->cpu_dev,
+				"over loop count, failed to set voltage\n");
+			return -EINVAL;
+		}
+	} while (vproc != new_vproc || vsram != new_vsram);
 
 	return 0;
 }
@@ -261,8 +207,8 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
 	 * If the new voltage or the intermediate voltage is higher than the
 	 * current voltage, scale up voltage first.
 	 */
-	target_vproc = (inter_vproc > vproc) ? inter_vproc : vproc;
-	if (pre_vproc < target_vproc) {
+	target_vproc = max(inter_vproc, vproc);
+	if (pre_vproc <= target_vproc) {
 		ret = mtk_cpufreq_set_voltage(info, target_vproc);
 		if (ret) {
 			dev_err(cpu_dev,
@@ -417,6 +363,15 @@ static int mtk_cpu_dvfs_info_init(struct mtk_cpu_dvfs_info *info, int cpu)
 	 */
 	info->need_voltage_tracking = (info->sram_reg != NULL);
 
+	/*
+	 * We assume min voltage is 0 and tracking target voltage using
+	 * min_volt_shift for each iteration.
+	 * The vtrack_max is 3 times of expeted iteration count.
+	 */
+	info->vtrack_max = 3 * DIV_ROUND_UP(max(info->soc_data->sram_max_volt,
+						info->soc_data->proc_max_volt),
+					    info->soc_data->min_volt_shift);
+
 	return 0;
 
 out_disable_inter_clock: