linux-kernel - [PATCH V3 10/15] cpufreq: mediatek: Add counter to prevent infinite loop when tracking voltage

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Date:   Fri, 15 Apr 2022 13:59:11 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     <rafael@...nel.org>, <viresh.kumar@...aro.org>,
        <robh+dt@...nel.org>, <krzk+dt@...nel.org>,
        <matthias.bgg@...il.com>
CC:     <jia-wei.chang@...iatek.com>, <roger.lu@...iatek.com>,
        <hsinyi@...gle.com>, <khilman@...libre.com>,
        <angelogioacchino.delregno@...labora.com>,
        <linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        Rex-BC Chen <rex-bc.chen@...iatek.com>
Subject: [PATCH V3 10/15] cpufreq: mediatek: Add counter to prevent infinite loop when tracking voltage

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: Rex-BC Chen <rex-bc.chen@...iatek.com>
---
 drivers/cpufreq/mediatek-cpufreq.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/cpufreq/mediatek-cpufreq.c b/drivers/cpufreq/mediatek-cpufreq.c
index cc44a7a9427a..d4c00237e862 100644
--- a/drivers/cpufreq/mediatek-cpufreq.c
+++ b/drivers/cpufreq/mediatek-cpufreq.c
@@ -86,6 +86,16 @@ 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_max;
+
+	/*
+	 * 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.
+	 */
+	retry_max = 3 * DIV_ROUND_UP(max(info->soc_data->sram_max_volt,
+					 info->soc_data->proc_max_volt),
+				     info->soc_data->min_volt_shift);
 
 	pre_vproc = regulator_get_voltage(proc_reg);
 	if (pre_vproc < 0) {
@@ -151,6 +161,12 @@ static int mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
 
 		pre_vproc = vproc;
 		pre_vsram = vsram;
+
+		if (--retry_max < 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;
-- 
2.18.0