cpufreq: mediatek: Record previous target vproc value

We found the buck voltage may not be exactly the same with what we set
because CPU may share the same buck with other module.
Therefore, we need to record the previous desired value instead of reading
it from regulators.

Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
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

@@ -40,6 +40,7 @@ struct mtk_cpu_dvfs_info {
 	struct list_head list_head;
 	int intermediate_voltage;
 	bool need_voltage_tracking;
+	int pre_vproc;
 };
 
 static LIST_HEAD(dvfs_info_list);
@@ -191,11 +192,17 @@ static int mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
 
 static int mtk_cpufreq_set_voltage(struct mtk_cpu_dvfs_info *info, int vproc)
 {
+	int ret;
+
 	if (info->need_voltage_tracking)
-		return mtk_cpufreq_voltage_tracking(info, vproc);
+		ret = mtk_cpufreq_voltage_tracking(info, vproc);
 	else
-		return regulator_set_voltage(info->proc_reg, vproc,
-					     vproc + VOLT_TOL);
+		ret = regulator_set_voltage(info->proc_reg, vproc,
+					    MAX_VOLT_LIMIT);
+	if (!ret)
+		info->pre_vproc = vproc;
+
+	return ret;
 }
 
 static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
@@ -213,7 +220,12 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
 	inter_vproc = info->intermediate_voltage;
 
 	pre_freq_hz = clk_get_rate(cpu_clk);
-	pre_vproc = regulator_get_voltage(info->proc_reg);
+
+	if (unlikely(info->pre_vproc <= 0))
+		pre_vproc = regulator_get_voltage(info->proc_reg);
+	else
+		pre_vproc = info->pre_vproc;
+
 	if (pre_vproc < 0) {
 		dev_err(cpu_dev, "invalid Vproc value: %d\n", pre_vproc);
 		return pre_vproc;