Date:	Mon, 17 Aug 2015 19:39:10 +0100
From:	Javi Merino <javi.merino@....com>
To:	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"cw00.choi@...sung.com" <cw00.choi@...sung.com>,
	"rufus.hamade@...tec.com" <rufus.hamade@...tec.com>,
	Ørjan Eide <Orjan.Eide@....com>,
	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>
Subject: Re: [PATCH v4 3/5] thermal: Add devfreq cooling

Replying to myself, there are two issues that will be fixed in the
next version:

On Fri, Aug 14, 2015 at 06:56:58PM +0100, Javi Merino wrote:
> From: Ørjan Eide <orjan.eide@....com>
> 
> Add a generic thermal cooling device for devfreq, that is similar to
> cpu_cooling.
> 
> The device must use devfreq.  In order to use the power extension of the
> cooling device, it must have registered its OPPs using the OPP library.
> 
> Cc: Zhang Rui <rui.zhang@...el.com>
> Cc: Eduardo Valentin <edubezval@...il.com>
> Signed-off-by: Javi Merino <javi.merino@....com>
> Signed-off-by: Ørjan Eide <orjan.eide@....com>
> ---
>  drivers/thermal/Kconfig           |  10 +
>  drivers/thermal/Makefile          |   3 +
>  drivers/thermal/devfreq_cooling.c | 541 ++++++++++++++++++++++++++++++++++++++
>  include/linux/devfreq_cooling.h   |  72 +++++
>  4 files changed, 626 insertions(+)
>  create mode 100644 drivers/thermal/devfreq_cooling.c
>  create mode 100644 include/linux/devfreq_cooling.h
> 
> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index 118938ee8552..da339ff7c3c9 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -147,6 +147,16 @@ config CLOCK_THERMAL
>           device that is configured to use this cooling mechanism will be
>           controlled to reduce clock frequency whenever temperature is high.
> 
> +config DEVFREQ_THERMAL
> +       bool "Generic device cooling support"
> +       depends on PM_DEVFREQ
> +       help
> +         This implements the generic devfreq cooling mechanism through
> +         frequency reduction for devices using devfreq.
> +
> +         This will throttle the device by limiting the maximum allowed DVFS
> +         frequency corresponding to the cooling level.
> +
>           If you want this support, you should say Y here.
> 
>  config THERMAL_EMULATION
> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> index 535dfee1496f..45f26978ff74 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -22,6 +22,9 @@ thermal_sys-$(CONFIG_CPU_THERMAL)     += cpu_cooling.o
>  # clock cooling
>  thermal_sys-$(CONFIG_CLOCK_THERMAL)    += clock_cooling.o
> 
> +# devfreq cooling
> +thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
> +
>  # platform thermal drivers
>  obj-$(CONFIG_QCOM_SPMI_TEMP_ALARM)     += qcom-spmi-temp-alarm.o
>  obj-$(CONFIG_SPEAR_THERMAL)    += spear_thermal.o
> diff --git a/drivers/thermal/devfreq_cooling.c b/drivers/thermal/devfreq_cooling.c
> new file mode 100644
> index 000000000000..ca2e212ce7ef
> --- /dev/null
> +++ b/drivers/thermal/devfreq_cooling.c
> @@ -0,0 +1,541 @@
> +/*
> + * devfreq_cooling: Thermal cooling device implementation for devices using
> + *                  devfreq
> + *
> + * Copyright (C) 2014-2015 ARM Limited
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * TODO:
> + *    - If OPPs are added or removed after devfreq cooling has
> + *      registered, the devfreq cooling won't react to it.
> + */
> +
> +#include <linux/devfreq.h>
> +#include <linux/devfreq_cooling.h>
> +#include <linux/export.h>
> +#include <linux/slab.h>
> +#include <linux/pm_opp.h>
> +#include <linux/thermal.h>
> +
> +static DEFINE_MUTEX(devfreq_lock);
> +static DEFINE_IDR(devfreq_idr);
> +
> +/**
> + * struct devfreq_cooling_device - Devfreq cooling device
> + * @id:                unique integer value corresponding to each
> + *             devfreq_cooling_device registered.
> + * @cdev:      Pointer to associated thermal cooling device.
> + * @devfreq:   Pointer to associated devfreq device.
> + * @cooling_state:     Current cooling state.
> + * @power_table:       Pointer to table with maximum power draw for each
> + *                     cooling state. State is the index into the table, and
> + *                     the power is in mW.
> + * @freq_table:        Pointer to a table with the frequencies sorted in descending
> + *             order.  You can index the table by cooling device state
> + * @freq_table_size:   size of the @freq_table and @power_table
> + * @power_ops: Pointer to power operations, used to generate @power_table.
> + */
> +struct devfreq_cooling_device {
> +       int id;
> +       struct thermal_cooling_device *cdev;
> +       struct devfreq *devfreq;
> +       unsigned long cooling_state;
> +       u32 *power_table;
> +       u32 *freq_table;
> +       size_t freq_table_size;
> +       struct devfreq_cooling_ops *power_ops;
> +};
> +
> +/**
> + * get_idr - function to get a unique id.
> + * @idr: struct idr * handle used to create a id.
> + * @id: int * value generated by this function.
> + *
> + * This function will populate @id with an unique
> + * id, using the idr API.
> + *
> + * Return: 0 on success, an error code on failure.
> + */
> +static int get_idr(struct idr *idr, int *id)
> +{
> +       int ret;
> +
> +       mutex_lock(&devfreq_lock);
> +       ret = idr_alloc(idr, NULL, 0, 0, GFP_KERNEL);
> +       mutex_unlock(&devfreq_lock);
> +       if (unlikely(ret < 0))
> +               return ret;
> +       *id = ret;
> +
> +       return 0;
> +}
> +
> +/**
> + * release_idr - function to free the unique id.
> + * @idr: struct idr * handle used for creating the id.
> + * @id: int value representing the unique id.
> + */
> +static void release_idr(struct idr *idr, int id)
> +{
> +       mutex_lock(&devfreq_lock);
> +       idr_remove(idr, id);
> +       mutex_unlock(&devfreq_lock);
> +}
> +
> +/**
> + * enable_disable_opps() - disable all opps above a given state
> + * @dfc:       Pointer to devfreq we are operating on
> + * @cdev_state:        cooling device state we're setting
> + *
> + * Go through the OPPs of the device, enabling all OPPs until
> + * @cdev_state and disabling those frequencies above it.
> + */
> +static int enable_disable_opps(struct devfreq_cooling_device *dfc,
> +                              unsigned long cdev_state)
> +{
> +       int i;
> +       struct device *dev = dfc->devfreq->dev.parent;
> +
> +       rcu_read_lock();
> +
> +       for (i = 0; i < dfc->freq_table_size; i++) {
> +               struct dev_pm_opp *opp;
> +               unsigned int freq = dfc->freq_table[i];
> +               bool want_enable = i >= cdev_state ? true : false;
> +
> +               opp = dev_pm_opp_find_freq_exact(dev, freq, !want_enable);
> +
> +               if (PTR_ERR(opp) == -ERANGE) {
> +                       continue;
> +               } else if (IS_ERR(opp)) {
> +                       rcu_read_unlock();
> +                       return PTR_ERR(opp);
> +               }
> +
> +               if (want_enable)
> +                       dev_pm_opp_enable(dev, freq);
> +               else
> +                       dev_pm_opp_disable(dev, freq);

dev_pm_opp_enable/disable can't be called while holding rcu.  The
rcu_read_lock() should only be held for the call to
dev_pm_opp_find_freq_exact()

> +       }
> +
> +       rcu_read_unlock();
> +
> +       return 0;
> +}
> +
> +static int devfreq_cooling_get_max_state(struct thermal_cooling_device *cdev,
> +                                        unsigned long *state)
> +{
> +       struct devfreq_cooling_device *dfc = cdev->devdata;
> +
> +       *state = dfc->freq_table_size - 1;
> +
> +       return 0;
> +}
> +
> +static int devfreq_cooling_get_cur_state(struct thermal_cooling_device *cdev,
> +                                        unsigned long *state)
> +{
> +       struct devfreq_cooling_device *dfc = cdev->devdata;
> +
> +       *state = dfc->cooling_state;
> +
> +       return 0;
> +}
> +
> +static int devfreq_cooling_set_cur_state(struct thermal_cooling_device *cdev,
> +                                        unsigned long state)
> +{
> +       struct devfreq_cooling_device *dfc = cdev->devdata;
> +       struct devfreq *df = dfc->devfreq;
> +       struct device *dev = df->dev.parent;
> +       int ret;
> +
> +       if (state == dfc->cooling_state)
> +               return 0;
> +
> +       dev_dbg(dev, "Setting cooling state %lu\n", state);
> +
> +       if (state >= dfc->freq_table_size)
> +               return -EINVAL;
> +
> +       ret = enable_disable_opps(dfc, state);
> +       if (ret)
> +               return ret;
> +
> +       dfc->cooling_state = state;
> +
> +       return 0;
> +}
> +
> +/**
> + * freq_get_state() - get the cooling state corresponding to a frequency
> + * @dfc:       Pointer to devfreq cooling device
> + * @freq:      frequency in Hz
> + *
> + * Return: the cooling state associated with the @freq, or
> + * THERMAL_CSTATE_INVALID if it wasn't found.
> + */
> +static unsigned long
> +freq_get_state(struct devfreq_cooling_device *dfc, unsigned long freq)
> +{
> +       int i;
> +
> +       for (i = 0; i < dfc->freq_table_size; i++) {
> +               if (dfc->freq_table[i] == freq)
> +                       return i;
> +       }
> +
> +       return THERMAL_CSTATE_INVALID;
> +}
> +
> +/**
> + * state_get_freq() - get the frequency corresponding to a cooling state
> + * @dfc:       Pointer to devfreq cooling device
> + * @state:     cooling device state
> + *
> + * Return: the frequency for this cooling device state or 0 for
> + * invalid states.
> + */
> +static unsigned long
> +state_get_freq(struct devfreq_cooling_device *dfc, unsigned long state)
> +{
> +       if (state >= dfc->freq_table_size) {
> +               dev_warn(dfc->devfreq->dev.parent,
> +                        "State %lu bigger than frequency table\n", state);
> +               return 0;
> +       }
> +
> +       return dfc->freq_table[state];
> +}
> +
> +static unsigned long
> +get_static_power(struct devfreq_cooling_device *dfc, unsigned long freq)
> +{
> +       struct devfreq *df = dfc->devfreq;
> +       struct device *dev = df->dev.parent;
> +       unsigned long voltage;
> +       struct dev_pm_opp *opp;
> +
> +       rcu_read_lock();
> +
> +       opp = dev_pm_opp_find_freq_exact(dev, freq, true);
> +       if (IS_ERR(opp) && (PTR_ERR(opp) == -ERANGE))
> +               opp = dev_pm_opp_find_freq_exact(dev, freq, false);
> +
> +       voltage = dev_pm_opp_get_voltage_always(opp) / 1000; /* mV */
> +
> +       rcu_read_unlock();
> +
> +       if (voltage == 0) {
> +               dev_warn_ratelimited(dev,
> +                                    "Failed to get voltage for frequency %lu: %ld\n",
> +                                    freq, IS_ERR(opp) ? PTR_ERR(opp) : 0);
> +               return 0;
> +       }
> +
> +       return dfc->power_ops->get_static_power(voltage);
> +}
> +
> +static int devfreq_cooling_get_requested_power(struct thermal_cooling_device *cdev,
> +                                              struct thermal_zone_device *tz,
> +                                              u32 *power)
> +{
> +       struct devfreq_cooling_device *dfc = cdev->devdata;
> +       struct devfreq *df = dfc->devfreq;
> +       struct devfreq_dev_status *status = &df->last_status;
> +       unsigned long state;
> +       unsigned long freq = status->current_frequency;
> +       u32 dyn_power, static_power;
> +
> +       /* Get dynamic power for state */
> +       state = freq_get_state(dfc, freq);
> +       if (state == THERMAL_CSTATE_INVALID)
> +               return -EAGAIN;
> +
> +       dyn_power = dfc->power_table[state];
> +
> +       /* Scale dynamic power for utilization */
> +       dyn_power = (dyn_power * status->busy_time) / status->total_time;
> +
> +       /* Get static power */
> +       static_power = get_static_power(dfc, freq);
> +
> +       *power = dyn_power + static_power;
> +
> +       return 0;
> +}
> +
> +static int devfreq_cooling_state2power(struct thermal_cooling_device *cdev,
> +                                      struct thermal_zone_device *tz,
> +                                      unsigned long state,
> +                                      u32 *power)
> +{
> +       struct devfreq_cooling_device *dfc = cdev->devdata;
> +       unsigned long freq;
> +       u32 static_power;
> +
> +       freq = state_get_freq(dfc, state);
> +       static_power = get_static_power(dfc, freq);
> +
> +       *power = dfc->power_table[state] + static_power;
> +       return 0;
> +}
> +
> +static int devfreq_cooling_power2state(struct thermal_cooling_device *cdev,
> +                                      struct thermal_zone_device *tz,
> +                                      u32 power, unsigned long *state)
> +{
> +       struct devfreq_cooling_device *dfc = cdev->devdata;
> +       struct devfreq *df = dfc->devfreq;
> +       struct devfreq_dev_status *status = &df->last_status;
> +       unsigned long freq = status->current_frequency;
> +       unsigned long busy_time;
> +       s32 dyn_power;
> +       u32 static_power;
> +       int i;
> +
> +       static_power = get_static_power(dfc, freq);
> +
> +       dyn_power = power - static_power;
> +       dyn_power = dyn_power > 0 ? dyn_power : 0;
> +
> +       /* Scale dynamic power for utilization */
> +       busy_time = status->busy_time ?: 1;
> +       dyn_power = (dyn_power * status->total_time) / busy_time;
> +
> +       /*
> +        * Find the first cooling state that is within the power
> +        * budget for dynamic power.
> +        */
> +       for (i = 0; i < dfc->freq_table_size - 1; i++)
> +               if (dyn_power >= dfc->power_table[i])
> +                       break;
> +
> +       *state = i;
> +       return 0;
> +}
> +
> +static struct thermal_cooling_device_ops devfreq_cooling_ops = {
> +       .get_max_state = devfreq_cooling_get_max_state,
> +       .get_cur_state = devfreq_cooling_get_cur_state,
> +       .set_cur_state = devfreq_cooling_set_cur_state,
> +};
> +
> +/**
> + * devfreq_cooling_gen_tables() - Generate power and freq tables.
> + * @dfc: Pointer to devfreq cooling device.
> + *
> + * Generate power and frequency tables: the power table hold the
> + * device's maximum power usage at each cooling state (OPP).  The
> + * static and dynamic power using the appropriate voltage and
> + * frequency for the state, is acquired from the struct
> + * devfreq_cooling_ops, and summed to make the maximum power draw.
> + *
> + * The frequency table holds the frequencies in descending order.
> + * That way its indexed by cooling device state.
> + *
> + * The tables are malloced, and pointers put in dfc.  They must be
> + * freed when unregistering the devfreq cooling device.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +static int devfreq_cooling_gen_tables(struct devfreq_cooling_device *dfc)
> +{
> +       struct devfreq *df = dfc->devfreq;
> +       struct device *dev = df->dev.parent;
> +       int ret, num_opps;
> +       struct devfreq_cooling_ops *callbacks = dfc->power_ops;
> +       unsigned long freq;
> +       u32 *power_table, *freq_table;
> +       int i;
> +
> +       if (!IS_ENABLED(CONFIG_PM_OPP)) {
> +               dev_warn(dev, "Can't use power extensions of the devfreq cooling device without CONFIG_PM_OPP\n");
> +               return -EINVAL;
> +       }
> +
> +       rcu_read_lock();
> +       num_opps = dev_pm_opp_get_opp_count(dev);
> +
> +       power_table = kcalloc(num_opps, sizeof(*power_table), GFP_KERNEL);

kcalloc() may sleep.  We can't sleep while in an RCU read-side section.

Cheers,
Javi

> +       if (!power_table) {
> +               ret = -ENOMEM;
> +               goto unlock;
> +       }
> +
> +       freq_table = kcalloc(num_opps, sizeof(*freq_table),
> +                            GFP_KERNEL);
> +       if (!freq_table) {
> +               ret = -ENOMEM;
> +               goto free_power_table;
> +       }
> +
> +       for (i = 0, freq = ULONG_MAX; i < num_opps; i++, freq--) {
> +               unsigned long power_dyn, voltage;
> +               struct dev_pm_opp *opp;
> +
> +               opp = dev_pm_opp_find_freq_floor(dev, &freq);
> +               if (IS_ERR(opp)) {
> +                       ret = PTR_ERR(opp);
> +                       goto free_tables;
> +               }
> +
> +               voltage = dev_pm_opp_get_voltage(opp) / 1000; /* mV */
> +
> +               power_dyn = callbacks->get_dynamic_power(freq, voltage);
> +
> +               dev_info(dev, "Dynamic power table: %lu MHz @ %lu mV: %lu = %lu mW\n",
> +                        freq / 1000000, voltage, power_dyn, power_dyn);
> +
> +               power_table[i] = power_dyn;
> +               freq_table[i] = freq;
> +       }
> +       rcu_read_unlock();
> +
> +       dfc->power_table = power_table;
> +       dfc->freq_table = freq_table;
> +       dfc->freq_table_size = num_opps;
> +
> +       return 0;
> +
> +free_tables:
> +       kfree(freq_table);
> +free_power_table:
> +       kfree(power_table);
> +unlock:
> +       rcu_read_unlock();
> +
> +       return ret;
> +}
--
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