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PM / devfreq: rockchip_dmc: Avoid glitches due to slow CPU

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We weren't giving enough time for DMC to change frequencies
when the CPU was running slow.

Change-Id: I84e1a4ad7b5ccddafb0016f3d5d6eef147a58591
Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
This commit is contained in:
Finley Xiao
2017-05-15 10:12:34 +08:00
committed by Huang, Tao
parent 08e0c3fbe7
commit 2d299c096e
1 changed files with 44 additions and 9 deletions
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53
drivers/devfreq/rockchip_dmc.c
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@@ -18,6 +18,7 @@
#include <linux/arm-smccc.h>
#include <linux/clk.h>
#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/devfreq.h>
#include <linux/devfreq-event.h>
@@ -164,6 +165,7 @@ struct rockchip_dmcfreq {
struct regulator *vdd_center;
unsigned long rate, target_rate;
unsigned long volt, target_volt;
unsigned int min_cpu_freq;
};
static int rockchip_dmcfreq_target(struct device *dev, unsigned long *freq,
@@ -171,8 +173,10 @@ static int rockchip_dmcfreq_target(struct device *dev, unsigned long *freq,
{
struct rockchip_dmcfreq *dmcfreq = dev_get_drvdata(dev);
struct dev_pm_opp *opp;
struct cpufreq_policy *policy;
unsigned long old_clk_rate = dmcfreq->rate;
unsigned long temp_rate, target_volt, target_rate;
unsigned int cpu_cur, cpufreq_cur;
int err;
rcu_read_lock();
@@ -204,6 +208,40 @@ static int rockchip_dmcfreq_target(struct device *dev, unsigned long *freq,
mutex_lock(&dmcfreq->lock);
/*
* We need to prevent cpu hotplug from happening while a dmc freq rate
* change is happening.
*
* Do this before taking the policy rwsem to avoid deadlocks between the
* mutex that is locked/unlocked in cpu_hotplug_disable/enable. And it
* can also avoid deadlocks between the mutex that is locked/unlocked
* in get/put_online_cpus (such as store_scaling_max_freq()).
*/
get_online_cpus();
/*
* Go to specified cpufreq and block other cpufreq changes since
* set_rate needs to complete during vblank.
*/
cpu_cur = smp_processor_id();
policy = cpufreq_cpu_get(cpu_cur);
if (!policy) {
dev_err(dev, "cpu%d policy NULL\n", cpu_cur);
goto cpufreq;
}
down_write(&policy->rwsem);
cpufreq_cur = cpufreq_quick_get(cpu_cur);
/* If we're thermally throttled; don't change; */
if (dmcfreq->min_cpu_freq && cpufreq_cur < dmcfreq->min_cpu_freq) {
if (policy->max >= dmcfreq->min_cpu_freq)
__cpufreq_driver_target(policy, dmcfreq->min_cpu_freq,
CPUFREQ_RELATION_L);
else
dev_dbg(dev, "CPU may too slow for DMC (%d MHz)\n",
policy->max);
}
/*
* If frequency scaling from low to high, adjust voltage first.
* If frequency scaling from high to low, adjust frequency first.
@@ -218,16 +256,7 @@ static int rockchip_dmcfreq_target(struct device *dev, unsigned long *freq,
}
}
/*
* We need to prevent cpu hotplug from happening while a dmc freq rate
* change is happening.
*/
get_online_cpus();
err = clk_set_rate(dmcfreq->dmc_clk, target_rate);
put_online_cpus();
if (err) {
dev_err(dev, "Cannot set frequency %lu (%d)\n",
target_rate, err);
@@ -262,6 +291,11 @@ static int rockchip_dmcfreq_target(struct device *dev, unsigned long *freq,
dmcfreq->volt = target_volt;
out:
__cpufreq_driver_target(policy, cpufreq_cur, CPUFREQ_RELATION_L);
up_write(&policy->rwsem);
cpufreq_cpu_put(policy);
cpufreq:
put_online_cpus();
mutex_unlock(&dmcfreq->lock);
return err;
}
@@ -890,6 +924,7 @@ static int rockchip_dmcfreq_probe(struct platform_device *pdev)
&data->ondemand_data.upthreshold);
of_property_read_u32(np, "downdifferential",
&data->ondemand_data.downdifferential);
of_property_read_u32(np, "min-cpu-freq", &data->min_cpu_freq);
data->rate = clk_get_rate(data->dmc_clk);
data->volt = regulator_get_voltage(data->vdd_center);