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

[Viresh Kumar]

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@xxxxxxxxxxxxxx>
> ---
>  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@xxxxxxxxxx>

-- 
viresh
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