Re: [PATCH v2 4/5] cpufreq-dt: Handle OPP voltage adjust events

Viresh Kumar
2015-09-22T17:36:43Z

On 18-09-15, 17:52, Stephen Boyd wrote:
> 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 | 63 +++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 57 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
> index 7c0d70e2a861..1bf3ae4d4ee1 100644
> --- a/drivers/cpufreq/cpufreq-dt.c
> +++ b/drivers/cpufreq/cpufreq-dt.c
> @@ -34,6 +34,9 @@ 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 struct freq_attr *cpufreq_dt_attr[] = {
> @@ -42,6 +45,33 @@ static struct freq_attr *cpufreq_dt_attr[] = {
> NULL,
> };
>
> +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;
> +
> + if (event == 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: %d\n", ret);
> + }
> +
> + return notifier_from_errno(ret);
> +}
> +
> static int set_target(struct cpufreq_policy *policy, unsigned int index)
> {
> struct dev_pm_opp *opp;
> @@ -53,6 +83,7 @@ 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);
> @@ -63,8 +94,8 @@ 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);
> @@ -72,7 +103,8 @@ 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);
> @@ -93,7 +125,7 @@ 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;
> }
> }
>
> @@ -102,7 +134,7 @@ 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 */
> @@ -112,9 +144,12 @@ 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;
> }
>
> @@ -201,6 +236,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> unsigned int transition_latency;
> bool need_update = false;
> int ret;
> + struct srcu_notifier_head *opp_srcu_head;
>
> ret = allocate_resources(policy->cpu, &cpu_dev, &cpu_reg, &cpu_clk);
> if (ret) {
> @@ -277,6 +313,19 @@ 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 (!transition_latency)
> @@ -326,7 +375,7 @@ 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;
> @@ -365,6 +414,8 @@ 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:

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

--
viresh