[PATCH 5/6] cpufreq-dt: Handle OPP voltage adjust events

Stephen Boyd
2015-06-02T01:49:42Z

On some SoCs the Adaptive Voltage Scaling (AVS) technique is
employed to optimize the operating voltage of a device. At a
given frequency, the hardware monitors dynamic factors and either
makes a suggestion for how much to adjust a voltage for the
current frequency, or it automatically adjusts the voltage
without software intervention.

In the former case, an AVS driver will call
dev_pm_opp_modify_voltage() and update the voltage for the
particular OPP the CPUs are using. Add an OPP notifier to
cpufreq-dt so that we can adjust the voltage of the CPU when AVS
updates the OPP.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
drivers/cpufreq/cpufreq-dt.c | 73 ++++++++++++++++++++++++++++++++++++++++----
1 file changed, 67 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
index bab67db54b7e..616218f133be 100644
--- a/drivers/cpufreq/cpufreq-dt.c
+++ b/drivers/cpufreq/cpufreq-dt.c
@@ -34,8 +34,48 @@ struct private_data {
struct regulator *cpu_reg;
struct thermal_cooling_device *cdev;
unsigned int voltage_tolerance; /* in percentage */
+ struct notifier_block opp_nb;
+ struct mutex lock;
+ unsigned long opp_freq;
};

+
+static int opp_notifier(struct notifier_block *nb, unsigned long event,
+ void *data)
+{
+ struct dev_pm_opp *opp = data;
+ struct private_data *priv = container_of(nb, struct private_data,
+ opp_nb);
+ struct device *cpu_dev = priv->cpu_dev;
+ struct regulator *cpu_reg = priv->cpu_reg;
+ unsigned long volt, tol, freq;
+ int ret = 0;
+
+ switch (event) {
+ case OPP_EVENT_ADJUST_VOLTAGE:
+ volt = dev_pm_opp_get_voltage(opp);
+ freq = dev_pm_opp_get_freq(opp);
+ tol = volt * priv->voltage_tolerance / 100;
+
+ mutex_lock(&priv->lock);
+ if (freq == priv->opp_freq)
+ ret = regulator_set_voltage_tol(cpu_reg, volt,
+ tol);
+ mutex_unlock(&priv->lock);
+ if (ret) {
+ dev_err(cpu_dev,
+ "failed to scale voltage up: %d\n",
+ ret);
+ return ret;
+ }
+ break;
+ default:
+ break;
+ }
+
+ return 0;
+}
+
static int set_target(struct cpufreq_policy *policy, unsigned int index)
{
struct dev_pm_opp *opp;
@@ -47,6 +87,7 @@ static int set_target(struct cpufreq_policy *policy, unsigned int index)
unsigned long volt = 0, volt_old = 0, tol = 0;
unsigned int old_freq, new_freq;
long freq_Hz, freq_exact;
+ unsigned long opp_freq = 0;
int ret;

freq_Hz = clk_round_rate(cpu_clk, freq_table[index].frequency * 1000);
@@ -57,8 +98,8 @@ static int set_target(struct cpufreq_policy *policy, unsigned int index)
new_freq = freq_Hz / 1000;
old_freq = clk_get_rate(cpu_clk) / 1000;

+ mutex_lock(&priv->lock);
if (!IS_ERR(cpu_reg)) {
- unsigned long opp_freq;

rcu_read_lock();
opp = dev_pm_opp_find_freq_ceil(cpu_dev, &freq_Hz);
@@ -66,7 +107,8 @@ static int set_target(struct cpufreq_policy *policy, unsigned int index)
rcu_read_unlock();
dev_err(cpu_dev, "failed to find OPP for %ld\n",
freq_Hz);
- return PTR_ERR(opp);
+ ret = PTR_ERR(opp);
+ goto out;
}
volt = dev_pm_opp_get_voltage(opp);
opp_freq = dev_pm_opp_get_freq(opp);
@@ -87,7 +129,7 @@ static int set_target(struct cpufreq_policy *policy, unsigned int index)
if (ret) {
dev_err(cpu_dev, "failed to scale voltage up: %d\n",
ret);
- return ret;
+ goto out;
}
}

@@ -96,7 +138,7 @@ static int set_target(struct cpufreq_policy *policy, unsigned int index)
dev_err(cpu_dev, "failed to set clock rate: %d\n", ret);
if (!IS_ERR(cpu_reg) && volt_old > 0)
regulator_set_voltage_tol(cpu_reg, volt_old, tol);
- return ret;
+ goto out;
}

/* scaling down? scale voltage after frequency */
@@ -106,9 +148,12 @@ static int set_target(struct cpufreq_policy *policy, unsigned int index)
dev_err(cpu_dev, "failed to scale voltage down: %d\n",
ret);
clk_set_rate(cpu_clk, old_freq * 1000);
+ goto out;
}
}
-
+ priv->opp_freq = opp_freq;
+out:
+ mutex_unlock(&priv->lock);
return ret;
}

@@ -194,6 +239,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
unsigned long min_uV = ~0, max_uV = 0;
unsigned int transition_latency;
int ret;
+ struct srcu_notifier_head *opp_srcu_head;

ret = allocate_resources(policy->cpu, &cpu_dev, &cpu_reg, &cpu_clk);
if (ret) {
@@ -228,6 +274,19 @@ static int cpufreq_init(struct cpufreq_policy *policy)
goto out_free_opp;
}

+ mutex_init(&priv->lock);
+
+ opp_srcu_head = dev_pm_opp_get_notifier(cpu_dev);
+ if (IS_ERR(opp_srcu_head)) {
+ ret = PTR_ERR(opp_srcu_head);
+ goto out_free_priv;
+ }
+
+ priv->opp_nb.notifier_call = opp_notifier;
+ ret = srcu_notifier_chain_register(opp_srcu_head, &priv->opp_nb);
+ if (ret)
+ goto out_free_priv;
+
of_property_read_u32(np, "voltage-tolerance", &priv->voltage_tolerance);

if (of_property_read_u32(np, "clock-latency", &transition_latency))
@@ -276,7 +335,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
if (ret) {
pr_err("failed to init cpufreq table: %d\n", ret);
- goto out_free_priv;
+ goto out_unregister_nb;
}

priv->cpu_dev = cpu_dev;
@@ -303,6 +362,8 @@ static int cpufreq_init(struct cpufreq_policy *policy)

out_free_cpufreq_table:
dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
+out_unregister_nb:
+ srcu_notifier_chain_unregister(opp_srcu_head, &priv->opp_nb);
out_free_priv:
kfree(priv);
out_free_opp:
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,