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Message-ID: <51F92109.2060707@ti.com>
Date: Wed, 31 Jul 2013 09:36:57 -0500
From: Nishanth Menon <nm@...com>
To: Mike Turquette <mturquette@...aro.org>
CC: <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH RFC 2/3] clk: cpufreq helper for voltage scaling
On 07/07/2013 08:44 PM, Mike Turquette wrote:
> This patch builds on "clk: notifier handler for dynamic voltage scaling"
> by adding a CPUfreq-specific helper function for registering a clock
> rate-change notifier to scale regulator voltage as a function of clock
> rate.
>
> In particular this patch creates an instance of struct
> cpufreq_frequency_table and also calculate the voltage scaling latency,
> both of which are returned to the caller for use in the CPUfreq driver.
>
> Signed-off-by: Mike Turquette <mturquette@...aro.org>
> ---
> drivers/clk/clk-voltage-notifier.c | 71 ++++++++++++++++++++++++++++++++++++++
> include/linux/clk.h | 6 ++++
> 2 files changed, 77 insertions(+)
As stage 1 of the transition, I dont have any complaints, but for SoC
level, at least on OMAP, it is not just regulator and clock, we have
additional tweaks to do - like ABB, AVS etc.
What would you suggest as the strategy to introduce SoC specific
handlers for voltage notifiers that can co-exist with this?
>
> diff --git a/drivers/clk/clk-voltage-notifier.c b/drivers/clk/clk-voltage-notifier.c
> index cb6b85f..8e1707f 100644
> --- a/drivers/clk/clk-voltage-notifier.c
> +++ b/drivers/clk/clk-voltage-notifier.c
> @@ -10,6 +10,7 @@
> */
>
> #include <linux/clk.h>
> +#include <linux/cpufreq.h>
for example - we should not depend on cpufreq in a generic clock based
dvfs approach. we would like to allow devfreq also to transition to this.
> #include <linux/device.h>
> #include <linux/module.h>
> #include <linux/notifier.h>
> @@ -133,3 +134,73 @@ void of_clk_volt_notifier_unregister(struct notifier_block *nb)
> kfree(vsd);
> }
> EXPORT_SYMBOL_GPL(of_clk_volt_notifier_unregister);
> +
> +void of_clk_cpufreq_notifier_unregister(struct notifier_block *nb,
> + struct cpufreq_frequency_table *freq_table)
> +{
> + struct volt_scale_data *data = to_volt_scale_data(nb);
> + struct device *dev = data->dev;
> +
> + opp_free_cpufreq_table(dev, &freq_table);
> + of_clk_volt_notifier_unregister(nb);
> +}
> +EXPORT_SYMBOL_GPL(of_clk_cpufreq_notifier_unregister);
> +
> +/**
> + * of_clk_cpufreq_notifer_register - register clock notifier to scale voltage
> + * @dev: device that owns this scaling operation
> + * @np: pointer to device's DT node
> + * @clk: clock whose rate-change notifier triggers voltage scaling
> + * @supply: regulator id string
> + * @freq_table: pointer to uninitialized CPUfreq frequency scaling table
> + * @voltage_latency: worst case voltage scaling latency
> + */
> +struct notifier_block *of_clk_cpufreq_notifier_register(struct device *dev,
> + struct device_node *np, struct clk *clk, const char *supply,
> + struct cpufreq_frequency_table **table,
> + unsigned int *voltage_latency)
> +{
> + struct notifier_block *nb;
> + struct volt_scale_data *vsd;
> + struct opp *opp;
> + unsigned long min, max;
> + int ret, i;
> +
> + nb = of_clk_volt_notifier_register(dev, np, clk, supply,
> + voltage_latency);
> + if (IS_ERR(nb))
> + return nb;
> +
> + vsd = to_volt_scale_data(nb);
> +
> + ret = opp_init_cpufreq_table(dev, table);
> + if (ret) {
> + pr_err("failed to init cpufreq table: %d\n", ret);
> + goto err_unregister;
> + }
> +
> + /* find the min and max voltages and compute worst-case latency */
> + for (i = 0; table[0][i].frequency != CPUFREQ_TABLE_END; i++)
> + ;
> +
> + rcu_read_lock();
> + opp = opp_find_freq_exact(dev,
> + table[0][0].frequency * 1000, true);
> + min = opp_get_voltage(opp);
> + opp = opp_find_freq_exact(dev,
> + table[0][i-1].frequency * 1000, true);
> + max = opp_get_voltage(opp);
> + rcu_read_unlock();
> +
> + *voltage_latency = regulator_set_voltage_time(vsd->reg, min, max);
> + if (*voltage_latency < 0)
> + pr_warn("%s: failed to calculate voltage latency, %d\n",
> + __func__, ret);
> +
> + return nb;
> +
> +err_unregister:
> + of_clk_volt_notifier_unregister(nb);
> + return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(of_clk_cpufreq_notifier_register);
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index 85ea520..3104883 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -86,6 +86,12 @@ struct notifier_block *of_clk_volt_notifier_register(struct device *dev,
> struct device_node *np, struct clk *clk, const char *supply,
> int *voltage_latency);
> void of_clk_volt_notifier_unregister(struct notifier_block *nb);
> +struct notifier_block *of_clk_cpufreq_notifier_register(struct device *dev,
> + struct device_node *np, struct clk *clk, const char *supply,
> + struct cpufreq_frequency_table **table,
> + unsigned int *voltage_latency);
> +void of_clk_cpufreq_notifier_unregister(struct notifier_block *nb,
> + struct cpufreq_frequency_table *freq_table);
>
> #endif
>
>
--
Regards,
Nishanth Menon
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