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cpufreq: mediatek: Refine mtk_cpufreq_voltage_tracking()
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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>
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Jia-Wei Chang authored and Viresh Kumar committed May 6, 2022
1 parent ead858b commit 6a17b38
Showing 1 changed file with 51 additions and 96 deletions.
147 changes: 51 additions & 96 deletions drivers/cpufreq/mediatek-cpufreq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,15 +8,14 @@
#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>
#include <linux/platform_device.h>
#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;
Expand Down Expand Up @@ -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;
Expand All @@ -73,98 +73,52 @@ 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) {
dev_err(info->cpu_dev,
"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;

Expand All @@ -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;
}
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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:
Expand Down

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