On Fri, Aug 19, 2011 at 1:30 AM, MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx> wrote: > With OPPs, a device may have multiple operable frequency and voltage > sets. However, there can be multiple possible operable sets and a system > will need to choose one from them. In order to reduce the power > consumption (by reducing frequency and voltage) without affecting the > performance too much, a Dynamic Voltage and Frequency Scaling (DVFS) > scheme may be used. > > This patch introduces the DVFS capability to non-CPU devices with OPPs. > DVFS is a techique whereby the frequency and supplied voltage of a > device is adjusted on-the-fly. DVFS usually sets the frequency as low > as possible with given conditions (such as QoS assurance) and adjusts > voltage according to the chosen frequency in order to reduce power > consumption and heat dissipation. > > The generic DVFS for devices, DEVFREQ, may appear quite similar with > /drivers/cpufreq. However, CPUFREQ does not allow to have multiple > devices registered and is not suitable to have multiple heterogenous > devices with different (but simple) governors. > > Normally, DVFS mechanism controls frequency based on the demand for > the device, and then, chooses voltage based on the chosen frequency. > DEVFREQ also controls the frequency based on the governor's frequency > recommendation and let OPP pick up the pair of frequency and voltage > based on the recommended frequency. Then, the chosen OPP is passed to > device driver's "target" callback. > > When PM QoS is going to be used with the DEVFREQ device, the device > driver should enable OPPs that are appropriate with the current PM QoS > requests. In order to do so, the device driver may call opp_enable and > opp_disable at the notifier callback of PM QoS so that PM QoS's > update_target() call enables the appropriate OPPs. Note that at least > one of OPPs should be enabled at any time; be careful when there is a > transition. > > Signed-off-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx> > Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > > --- > The test code with board support for Exynos4-NURI is at > http://git.infradead.org/users/kmpark/linux-2.6-samsung/shortlog/refs/heads/devfreq > > --- > Thank you for your valuable comments, Rafael, Greg, Pavel, Colin, Mike, > and Kevin. > > Changes at v6-resubmit from v6 > - Use jiffy directly instead of ktime > - Be prepared for profile->polling_ms changes (not supported fully at > this stage) > > Changes from v5 > - Uses OPP availability change notifier > - Removed devfreq_interval. Uses one jiffy instead. DEVFREQ adjusts > polling interval based on the interval requirement of DEVFREQ > devices. > - Moved devfreq to /drivers/devfreq to accomodate devfreq-related files > including governors and devfreq drivers. > - Coding style revised. > - Updated devfreq_add_device interface to get tunable values. > > Changed from v4 > - Removed tickle, which is a duplicated feature; PM QoS can do the same. > - Allow to extend polling interval if devices have longer polling intervals. > - Relocated private data of governors. > - Removed system-wide sysfs > > Changed from v3 > - In kerneldoc comments, DEVFREQ has ben replaced by devfreq > - Revised removing devfreq entries with error mechanism > - Added and revised comments > - Removed unnecessary codes > - Allow to give a name to a governor > - Bugfix: a tickle call may cancel an older tickle call that is still in > effect. > > Changed from v2 > - Code style revised and cleaned up. > - Remove DEVFREQ entries that incur errors except for EAGAIN > - Bug fixed: tickle for devices without polling governors > > Changes from v1(RFC) > - Rename: DVFS --> DEVFREQ > - Revised governor design > . Governor receives the whole struct devfreq > . Governor should gather usage information (thru get_dev_status) itself > - Periodic monitoring runs only when needed. > - DEVFREQ no more deals with voltage information directly > - Removed some printks. > - Some cosmetics update > - Use freezable_wq. > --- > drivers/Kconfig | 2 + > drivers/Makefile | 2 + > drivers/devfreq/Kconfig | 39 ++++++ > drivers/devfreq/Makefile | 1 + > drivers/devfreq/devfreq.c | 312 +++++++++++++++++++++++++++++++++++++++++++++ > include/linux/devfreq.h | 111 ++++++++++++++++ > 6 files changed, 467 insertions(+), 0 deletions(-) > create mode 100644 drivers/devfreq/Kconfig > create mode 100644 drivers/devfreq/Makefile > create mode 100644 drivers/devfreq/devfreq.c > create mode 100644 include/linux/devfreq.h > > diff --git a/drivers/Kconfig b/drivers/Kconfig > index 95b9e7e..a1efd75 100644 > --- a/drivers/Kconfig > +++ b/drivers/Kconfig > @@ -130,4 +130,6 @@ source "drivers/iommu/Kconfig" > > source "drivers/virt/Kconfig" > > +source "drivers/devfreq/Kconfig" > + > endmenu > diff --git a/drivers/Makefile b/drivers/Makefile > index 7fa433a..97c957b 100644 > --- a/drivers/Makefile > +++ b/drivers/Makefile > @@ -127,3 +127,5 @@ obj-$(CONFIG_IOMMU_SUPPORT) += iommu/ > > # Virtualization drivers > obj-$(CONFIG_VIRT_DRIVERS) += virt/ > + > +obj-$(CONFIG_PM_DEVFREQ) += devfreq/ > diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig > new file mode 100644 > index 0000000..1fb42de > --- /dev/null > +++ b/drivers/devfreq/Kconfig > @@ -0,0 +1,39 @@ > +config ARCH_HAS_DEVFREQ > + bool > + depends on ARCH_HAS_OPP > + help > + Denotes that the architecture supports DEVFREQ. If the architecture > + supports multiple OPP entries per device and the frequency of the > + devices with OPPs may be altered dynamically, the architecture > + supports DEVFREQ. > + > +menuconfig PM_DEVFREQ > + bool "Generic Dynamic Voltage and Frequency Scaling (DVFS) support" > + depends on PM_OPP && ARCH_HAS_DEVFREQ > + help > + With OPP support, a device may have a list of frequencies and > + voltages available. DEVFREQ, a generic DVFS framework can be > + registered for a device with OPP support in order to let the > + governor provided to DEVFREQ choose an operating frequency > + based on the OPP's list and the policy given with DEVFREQ. > + > + Each device may have its own governor and policy. DEVFREQ can > + reevaluate the device state periodically and/or based on the > + OPP list changes (each frequency/voltage pair in OPP may be > + disabled or enabled). > + > + Like some CPUs with CPUFREQ, a device may have multiple clocks. > + However, because the clock frequencies of a single device are > + determined by the single device's state, an instance of DEVFREQ > + is attached to a single device and returns a "representative" > + clock frequency from the OPP of the device, which is also attached > + to a device by 1-to-1. The device registering DEVFREQ takes the > + responsiblity to "interpret" the frequency listed in OPP and > + to set its every clock accordingly with the "target" callback > + given to DEVFREQ. > + > +if PM_DEVFREQ > + > +comment "DEVFREQ Drivers" > + > +endif # PM_DEVFREQ > diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile > new file mode 100644 > index 0000000..168934a > --- /dev/null > +++ b/drivers/devfreq/Makefile > @@ -0,0 +1 @@ > +obj-$(CONFIG_PM_DEVFREQ) += devfreq.o > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c > new file mode 100644 > index 0000000..af848ffa > --- /dev/null > +++ b/drivers/devfreq/devfreq.c > @@ -0,0 +1,312 @@ > +/* > + * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework > + * for Non-CPU Devices Based on OPP. > + * > + * Copyright (C) 2011 Samsung Electronics > + * MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx> > + * > + * 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. > + */ > + > +#include <linux/kernel.h> > +#include <linux/errno.h> > +#include <linux/err.h> > +#include <linux/init.h> > +#include <linux/slab.h> > +#include <linux/opp.h> > +#include <linux/devfreq.h> > +#include <linux/workqueue.h> > +#include <linux/platform_device.h> > +#include <linux/list.h> > +#include <linux/printk.h> > +#include <linux/hrtimer.h> > + > +/* > + * devfreq_work periodically monitors every registered device. > + * The minimum polling interval is one jiffy. The polling interval is > + * determined by the minimum polling period among all polling devfreq > + * devices. The resolution of polling interval is one jiffy. > + */ > +static bool polling; > +static struct workqueue_struct *devfreq_wq; > +static struct delayed_work devfreq_work; > + > +/* The list of all device-devfreq */ > +static LIST_HEAD(devfreq_list); > +static DEFINE_MUTEX(devfreq_list_lock); > + > +/** > + * find_device_devfreq() - find devfreq struct using device pointer > + * @dev: device pointer used to lookup device devfreq. > + * > + * Search the list of device devfreqs and return the matched device's > + * devfreq info. devfreq_list_lock should be held by the caller. > + */ > +static struct devfreq *find_device_devfreq(struct device *dev) > +{ > + struct devfreq *tmp_devfreq; > + > + if (unlikely(IS_ERR_OR_NULL(dev))) { > + pr_err("DEVFREQ: %s: Invalid parameters\n", __func__); > + return ERR_PTR(-EINVAL); > + } > + > + list_for_each_entry(tmp_devfreq, &devfreq_list, node) { > + if (tmp_devfreq->dev == dev) > + return tmp_devfreq; > + } > + > + return ERR_PTR(-ENODEV); > +} > + > +/** > + * devfreq_do() - Check the usage profile of a given device and configure > + * frequency and voltage accordingly > + * @devfreq: devfreq info of the given device > + */ > +static int devfreq_do(struct devfreq *devfreq) > +{ > + struct opp *opp; > + unsigned long freq; > + int err; > + > + err = devfreq->governor->get_target_freq(devfreq, &freq); > + if (err) > + return err; > + > + opp = opp_find_freq_ceil(devfreq->dev, &freq); > + if (opp == ERR_PTR(-ENODEV)) > + opp = opp_find_freq_floor(devfreq->dev, &freq); > + > + if (IS_ERR(opp)) > + return PTR_ERR(opp); > + > + if (devfreq->previous_freq == freq) > + return 0; > + > + err = devfreq->profile->target(devfreq->dev, opp); > + if (err) > + return err; > + > + devfreq->previous_freq = freq; > + return 0; > +} > + > +/** > + * devfreq_update() - Notify that the device OPP has been changed. > + * @dev: the device whose OPP has been changed. > + */ > +static int devfreq_update(struct notifier_block *nb, unsigned long type, > + void *devp) > +{ > + struct devfreq *devfreq; > + int err = 0; > + > + mutex_lock(&devfreq_list_lock); > + devfreq = container_of(nb, struct devfreq, nb); > + /* Reevaluate the proper frequency */ > + err = devfreq_do(devfreq); > + mutex_unlock(&devfreq_list_lock); > + return err; > +} > + > +/** > + * devfreq_monitor() - Periodically run devfreq_do() > + * @work: the work struct used to run devfreq_monitor periodically. > + * > + */ > +static void devfreq_monitor(struct work_struct *work) > +{ > + static unsigned long last_polled_at; > + struct devfreq *devfreq, *tmp; > + int error; > + int jiffies_passed; > + unsigned long next_jiffies = ULONG_MAX, now = jiffies; > + > + /* Initially last_polled_at = 0, polling every device at bootup */ > + jiffies_passed = now - last_polled_at; > + last_polled_at = now; > + > + if (jiffies_passed == 0) > + jiffies_passed = 1; > + if (jiffies_passed < 0) /* "Infinite Timeout" */ > + jiffies_passed = INT_MAX; This doesn't account for jiffies rollover (~49 days on architectures with HZ == 1000). At rollover-time some devices might incorrectly get marked as having an infinite timeout. > + > + mutex_lock(&devfreq_list_lock); > + > + list_for_each_entry_safe(devfreq, tmp, &devfreq_list, node) { > + /* Reflect the changes in profile->polling_ms */ > + if (devfreq->polling_ms != devfreq->profile->polling_ms) { > + devfreq->polling_ms = devfreq->profile->polling_ms; > + devfreq->polling_jiffies = msecs_to_jiffies( > + devfreq->polling_ms); Does struct devfreq need ->polling_ms? It seems like useless storage since we're really interested in ->polling_jiffies. How about removing devfreq->polling_ms and then just doing the conversion whenever the sysfs file is written to? Regards, Mike > + if (devfreq->next_polling == 0 && > + devfreq->polling_jiffies) > + devfreq->next_polling = 1; /* Poll Now */ > + else if (devfreq->polling_jiffies == 0) > + devfreq->next_polling = 0; /* Stop Polling */ > + } > + if (devfreq->next_polling == 0) > + continue; > + > + /* > + * Reduce more next_polling if devfreq_wq took an extra > + * delay. (i.e., CPU has been idled.) > + */ > + if (devfreq->next_polling <= jiffies_passed) { > + error = devfreq_do(devfreq); > + > + /* Remove a devfreq with an error. */ > + if (error && error != -EAGAIN) { > + dev_err(devfreq->dev, "Due to devfreq_do error(%d), devfreq(%s) is removed from the device\n", > + error, devfreq->governor->name); > + > + list_del(&devfreq->node); > + kfree(devfreq); > + > + continue; > + } > + devfreq->next_polling = devfreq->polling_jiffies; > + > + /* No more polling required (polling_ms changed) */ > + if (devfreq->next_polling == 0) > + continue; > + } else { > + devfreq->next_polling -= jiffies_passed; > + } > + > + next_jiffies = (next_jiffies > devfreq->next_polling) ? > + devfreq->next_polling : next_jiffies; > + } > + > + if (next_jiffies > 0 && next_jiffies < ULONG_MAX) { > + polling = true; > + queue_delayed_work(devfreq_wq, &devfreq_work, next_jiffies); > + } else { > + polling = false; > + } > + > + mutex_unlock(&devfreq_list_lock); > +} > + > +/** > + * devfreq_add_device() - Add devfreq feature to the device > + * @dev: the device to add devfreq feature. > + * @profile: device-specific profile to run devfreq. > + * @governor: the policy to choose frequency. > + * @data: private data for the governor. The devfreq framework does not > + * touch this value. > + */ > +int devfreq_add_device(struct device *dev, struct devfreq_dev_profile *profile, > + struct devfreq_governor *governor, void *data) > +{ > + struct devfreq *devfreq; > + struct srcu_notifier_head *nh; > + int err = 0; > + > + if (!dev || !profile || !governor) { > + dev_err(dev, "%s: Invalid parameters.\n", __func__); > + return -EINVAL; > + } > + > + mutex_lock(&devfreq_list_lock); > + > + devfreq = find_device_devfreq(dev); > + if (!IS_ERR(devfreq)) { > + dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__); > + err = -EINVAL; > + goto out; > + } > + > + devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL); > + if (!devfreq) { > + dev_err(dev, "%s: Unable to create devfreq for the device\n", > + __func__); > + err = -ENOMEM; > + goto out; > + } > + > + devfreq->dev = dev; > + devfreq->profile = profile; > + devfreq->governor = governor; > + devfreq->polling_ms = profile->polling_ms; > + devfreq->next_polling = devfreq->polling_jiffies > + = msecs_to_jiffies(devfreq->polling_ms); > + devfreq->previous_freq = profile->initial_freq; > + devfreq->data = data; > + > + devfreq->nb.notifier_call = devfreq_update; > + nh = opp_get_notifier(dev); > + if (IS_ERR(nh)) { > + err = PTR_ERR(nh); > + goto out; > + } > + err = srcu_notifier_chain_register(nh, &devfreq->nb); > + if (err) > + goto out; > + > + list_add(&devfreq->node, &devfreq_list); > + > + if (devfreq_wq && devfreq->next_polling && !polling) { > + polling = true; > + queue_delayed_work(devfreq_wq, &devfreq_work, > + devfreq->next_polling); > + } > +out: > + mutex_unlock(&devfreq_list_lock); > + > + return err; > +} > + > +/** > + * devfreq_remove_device() - Remove devfreq feature from a device. > + * @device: the device to remove devfreq feature. > + */ > +int devfreq_remove_device(struct device *dev) > +{ > + struct devfreq *devfreq; > + struct srcu_notifier_head *nh; > + int err = 0; > + > + if (!dev) > + return -EINVAL; > + > + mutex_lock(&devfreq_list_lock); > + devfreq = find_device_devfreq(dev); > + if (IS_ERR(devfreq)) { > + err = PTR_ERR(devfreq); > + goto out; > + } > + > + nh = opp_get_notifier(dev); > + if (IS_ERR(nh)) { > + err = PTR_ERR(nh); > + goto out; > + } > + > + list_del(&devfreq->node); > + srcu_notifier_chain_unregister(nh, &devfreq->nb); > + kfree(devfreq); > +out: > + mutex_unlock(&devfreq_list_lock); > + return 0; > +} > + > +/** > + * devfreq_init() - Initialize data structure for devfreq framework and > + * start polling registered devfreq devices. > + */ > +static int __init devfreq_init(void) > +{ > + mutex_lock(&devfreq_list_lock); > + polling = false; > + devfreq_wq = create_freezable_workqueue("devfreq_wq"); > + INIT_DELAYED_WORK_DEFERRABLE(&devfreq_work, devfreq_monitor); > + mutex_unlock(&devfreq_list_lock); > + > + devfreq_monitor(&devfreq_work.work); > + return 0; > +} > +late_initcall(devfreq_init); > diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h > new file mode 100644 > index 0000000..18e94cb > --- /dev/null > +++ b/include/linux/devfreq.h > @@ -0,0 +1,111 @@ > +/* > + * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework > + * for Non-CPU Devices Based on OPP. > + * > + * Copyright (C) 2011 Samsung Electronics > + * MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx> > + * > + * 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. > + */ > + > +#ifndef __LINUX_DEVFREQ_H__ > +#define __LINUX_DEVFREQ_H__ > + > +#include <linux/notifier.h> > + > +#define DEVFREQ_NAME_LEN 16 > + > +struct devfreq; > +struct devfreq_dev_status { > + /* both since the last measure */ > + unsigned long total_time; > + unsigned long busy_time; > + unsigned long current_frequency; > +}; > + > +struct devfreq_dev_profile { > + unsigned long max_freq; /* may be larger than the actual value */ > + unsigned long initial_freq; > + int polling_ms; /* 0 for at opp change only */ > + > + int (*target)(struct device *dev, struct opp *opp); > + int (*get_dev_status)(struct device *dev, > + struct devfreq_dev_status *stat); > +}; > + > +/** > + * struct devfreq_governor - Devfreq policy governor > + * @name Governor's name > + * @get_target_freq Returns desired operating frequency for the device. > + * Basically, get_target_freq will run > + * devfreq_dev_profile.get_dev_status() to get the > + * status of the device (load = busy_time / total_time). > + */ > +struct devfreq_governor { > + char name[DEVFREQ_NAME_LEN]; > + int (*get_target_freq)(struct devfreq *this, unsigned long *freq); > +}; > + > +/** > + * struct devfreq - Device devfreq structure > + * @node list node - contains the devices with devfreq that have been > + * registered. > + * @dev device pointer > + * @profile device-specific devfreq profile > + * @governor method how to choose frequency based on the usage. > + * @nb notifier block registered to the corresponding OPP to get > + * notified for frequency availability updates. > + * @polling_jiffies interval in jiffies. > + * @polling_ms interval in ms. to compare with profile's polling_ms > + * and update polling_jiffies if the device has changed > + * the polling interval. > + * @previous_freq previously configured frequency value. > + * @next_polling the number of remaining jiffies to poll with > + * "devfreq_monitor" executions to reevaluate > + * frequency/voltage of the device. Set by > + * profile's polling_ms interval. > + * @data Private data of the governor. The devfreq framework does not > + * touch this. > + * > + * This structure stores the devfreq information for a give device. > + */ > +struct devfreq { > + struct list_head node; > + > + struct device *dev; > + struct devfreq_dev_profile *profile; > + struct devfreq_governor *governor; > + struct notifier_block nb; > + > + unsigned long polling_jiffies; > + int polling_ms; > + unsigned long previous_freq; > + unsigned int next_polling; > + > + void *data; /* private data for governors */ > +}; > + > +#if defined(CONFIG_PM_DEVFREQ) > +extern int devfreq_add_device(struct device *dev, > + struct devfreq_dev_profile *profile, > + struct devfreq_governor *governor, > + void *data); > +extern int devfreq_remove_device(struct device *dev); > +#else /* !CONFIG_PM_DEVFREQ */ > +static int devfreq_add_device(struct device *dev, > + struct devfreq_dev_profile *profile, > + struct devfreq_governor *governor, > + void *data) > +{ > + return 0; > +} > + > +static int devfreq_remove_device(struct device *dev) > +{ > + return 0; > +} > +#endif /* CONFIG_PM_DEVFREQ */ > + > +#endif /* __LINUX_DEVFREQ_H__ */ > -- > 1.7.4.1 > > _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
