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path: root/drivers/devfreq/Kconfig
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2016-07-06PM / devfreq: make exynos-bus ARM_EXYNOS_BUS_DEVFREQ tristatePaul Gortmaker
The Kconfig currently controlling compilation of this code is: devfreq/Kconfig:config ARM_EXYNOS_BUS_DEVFREQ devfreq/Kconfig: bool "ARM EXYNOS Generic Memory Bus DEVFREQ Driver" ...meaning that it currently is not being built as a module by anyone. Rather than rip out the existing modular code, Chanwoo indicated that he'd rather see the driver offered as tristate. I don't have the hardware for runtime validation, so this change is only validated for compile and modpost. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Acked-by: Chanwoo Choi <cw00.choi@samsung.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2016-05-03PM / devfreq: exynos: Remove unused exynos4/5 busfreq driverChanwoo Choi
This patch removes the unused exynos4/5 busfreq driver. Instead, generic exynos-bus frequency driver support the all Exynos SoCs. Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
2016-05-03PM / devfreq: exynos: Add support of bus frequency of sub-blocks using ↵Chanwoo Choi
passive governor This patch adds the support of bus frequency feature for sub-blocks which share the one power line. If each bus depends on the power line, each bus is not able to change the voltage by oneself. To optimize the power-consumption on runtime, some buses using the same power line should change the source clock and regulator at the same time. So, this patch uses the passive governor to support the bus frequency for all buses which sharing the one power line. For example, Exynos3250 include the two power line for AXI buses as following: : VDD_MIF : MIF (Memory Interface) provide the DMC (Dynamic Memory Controller) with the power (regulator). : VDD_INT : INT (Internal) provide the various sub-blocks with the power (regulator). Each bus is included in as follwoing block. In the case of VDD_MIF, only DMC bus use the power line. So, there is no any depencency between buese. But, in the case of VDD_INT, various buses share the one power line of VDD_INT. We need to make the depenency between buses. When using passive governor, there is no problem to support the bus frequency as DVFS for all buses. One bus should be operated as the parent bus device which gathering the current load of INT block and then decides the new frequency with some governors except of passive governor. After deciding the new frequency by the parent bus device, the rest bus devices will change the each source clock according to new frequency of the parent bus device. - MIF (Memory Interface) block : VDD_MIF |--- DMC - INT (Internal) block : VDD_INT |--- LEFTBUS (parent) |--- PERIL |--- MFC |--- G3D |--- RIGHTBUS |--- FSYS |--- LCD0 |--- PERIR |--- ISP |--- CAM Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com> [tjakobi: Reported debugfs error during booting and cw00.choi fix it.] Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
2016-05-03PM / devfreq: Add new passive governorChanwoo Choi
This patch adds the new passive governor for DEVFREQ framework. The following governors are already present and used for DVFS (Dynamic Voltage and Frequency Scaling) drivers. The following governors are independently used for one device driver which don't give the influence to other device drviers and also don't receive the effect from other device drivers. - ondemand / performance / powersave / userspace The passive governor depends on operation of parent driver with specific governos extremely and is not able to decide the new frequency by oneself. According to the decided new frequency of parent driver with governor, the passive governor uses it to decide the appropriate frequency for own device driver. The passive governor must need the following information from device tree: - the source clock and OPP tables - the instance of parent device For exameple, there are one more devfreq device drivers which need to change their source clock according to their utilization on runtime. But, they share the same power line (e.g., regulator). So, specific device driver is operated as parent with ondemand governor and then the rest device driver with passive governor is influenced by parent device. Suggested-by: Myungjoo Ham <myungjoo.ham@samsung.com> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com> [tjakobi: Reported RCU locking issue and cw00.choi fix it] Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de> [linux.amoon: Reported possible recursive locking and cw00.choi fix it] Reported-by: Anand Moon <linux.amoon@gmail.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
2016-05-03PM / devfreq: exynos: Add generic exynos bus frequency driverChanwoo Choi
This patch adds the generic exynos bus frequency driver for AMBA AXI bus of sub-blocks in exynos SoC with DEVFREQ framework. The Samsung Exynos SoC have the common architecture for bus between DRAM and sub-blocks in SoC. This driver can support the generic bus frequency driver for Exynos SoCs. In devicetree, Each bus block has a bus clock, regulator, operation-point and devfreq-event devices which measure the utilization of each bus block. Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com> [m.reichl and linux.amoon: Tested it on exynos4412-odroidu3 board] Tested-by: Markus Reichl <m.reichl@fivetechno.de> Tested-by: Anand Moon <linux.amoon@gmail.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
2016-03-17PM / devfreq: Spelling s/frequnecy/frequency/Geert Uytterhoeven
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-02-10Merge tag 'pm+acpi-3.20-rc1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm Pull ACPI and power management updates from Rafael Wysocki: "We have a few new features this time, including a new SFI-based cpufreq driver, a new devfreq driver for Tegra Activity Monitor, a new devfreq class for providing its governors with raw utilization data and a new ACPI driver for AMD SoCs. Still, the majority of changes here are reworks of existing code to make it more straightforward or to prepare it for implementing new features on top of it. The primary example is the rework of ACPI resources handling from Jiang Liu, Thomas Gleixner and Lv Zheng with support for IOAPIC hotplug implemented on top of it, but there is quite a number of changes of this kind in the cpufreq core, ACPICA, ACPI EC driver, ACPI processor driver and the generic power domains core code too. The most active developer is Viresh Kumar with his cpufreq changes. Specifics: - Rework of the core ACPI resources parsing code to fix issues in it and make using resource offsets more convenient and consolidation of some resource-handing code in a couple of places that have grown analagous data structures and code to cover the the same gap in the core (Jiang Liu, Thomas Gleixner, Lv Zheng). - ACPI-based IOAPIC hotplug support on top of the resources handling rework (Jiang Liu, Yinghai Lu). - ACPICA update to upstream release 20150204 including an interrupt handling rework that allows drivers to install raw handlers for ACPI GPEs which then become entirely responsible for the given GPE and the ACPICA core code won't touch it (Lv Zheng, David E Box, Octavian Purdila). - ACPI EC driver rework to fix several concurrency issues and other problems related to events handling on top of the ACPICA's new support for raw GPE handlers (Lv Zheng). - New ACPI driver for AMD SoCs analogous to the LPSS (Low-Power Subsystem) driver for Intel chips (Ken Xue). - Two minor fixes of the ACPI LPSS driver (Heikki Krogerus, Jarkko Nikula). - Two new blacklist entries for machines (Samsung 730U3E/740U3E and 510R) where the native backlight interface doesn't work correctly while the ACPI one does (Hans de Goede). - Rework of the ACPI processor driver's handling of idle states to make the code more straightforward and less bloated overall (Rafael J Wysocki). - Assorted minor fixes related to ACPI and SFI (Andreas Ruprecht, Andy Shevchenko, Hanjun Guo, Jan Beulich, Rafael J Wysocki, Yaowei Bai). - PCI core power management modification to avoid resuming (some) runtime-suspended devices during system suspend if they are in the right states already (Rafael J Wysocki). - New SFI-based cpufreq driver for Intel platforms using SFI (Srinidhi Kasagar). - cpufreq core fixes, cleanups and simplifications (Viresh Kumar, Doug Anderson, Wolfram Sang). - SkyLake CPU support and other updates for the intel_pstate driver (Kristen Carlson Accardi, Srinivas Pandruvada). - cpufreq-dt driver cleanup (Markus Elfring). - Init fix for the ARM big.LITTLE cpuidle driver (Sudeep Holla). - Generic power domains core code fixes and cleanups (Ulf Hansson). - Operating Performance Points (OPP) core code cleanups and kernel documentation update (Nishanth Menon). - New dabugfs interface to make the list of PM QoS constraints available to user space (Nishanth Menon). - New devfreq driver for Tegra Activity Monitor (Tomeu Vizoso). - New devfreq class (devfreq_event) to provide raw utilization data to devfreq governors (Chanwoo Choi). - Assorted minor fixes and cleanups related to power management (Andreas Ruprecht, Krzysztof Kozlowski, Rickard Strandqvist, Pavel Machek, Todd E Brandt, Wonhong Kwon). - turbostat updates (Len Brown) and cpupower Makefile improvement (Sriram Raghunathan)" * tag 'pm+acpi-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (151 commits) tools/power turbostat: relax dependency on APERF_MSR tools/power turbostat: relax dependency on invariant TSC Merge branch 'pci/host-generic' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci into acpi-resources tools/power turbostat: decode MSR_*_PERF_LIMIT_REASONS tools/power turbostat: relax dependency on root permission ACPI / video: Add disable_native_backlight quirk for Samsung 510R ACPI / PM: Remove unneeded nested #ifdef USB / PM: Remove unneeded #ifdef and associated dead code intel_pstate: provide option to only use intel_pstate with HWP ACPI / EC: Add GPE reference counting debugging messages ACPI / EC: Add query flushing support ACPI / EC: Refine command storm prevention support ACPI / EC: Add command flushing support. ACPI / EC: Introduce STARTED/STOPPED flags to replace BLOCKED flag ACPI: add AMD ACPI2Platform device support for x86 system ACPI / table: remove duplicate NULL check for the handler of acpi_table_parse() ACPI / EC: Update revision due to raw handler mode. ACPI / EC: Reduce ec_poll() by referencing the last register access timestamp. ACPI / EC: Fix several GPE handling issues by deploying ACPI_GPE_DISPATCH_RAW_HANDLER mode. ACPICA: Events: Enable APIs to allow interrupt/polling adaptive request based GPE handling model ...
2015-01-30PM / devfreq: event: Add devfreq_event classChanwoo Choi
This patch adds a new class in devfreq, devfreq_event, which provides raw data (e.g., memory bus utilization, GPU utilization) for devfreq governors. - devfreq_event device : Provides raw data for a governor of a devfreq device - devfreq device : Monitors device state and changes frequency/voltage of the device using the raw data from its devfreq_event device. A devfreq device dertermines performance states (normally the frequency and the voltage vlues) based on the results its designtated devfreq governor: e.g., ondemand, performance, powersave. In order to give such results required by a devfreq device, the devfreq governor requires data that indicates the performance requirement given to the devfreq device. The conventional (previous) implementatino of devfreq subsystem requires a devfreq device driver to implement its own mechanism to acquire performance requirement for its governor. However, there had been issues with such requirements: 1. Although performance requirement of such devices is usually acquired from common devices (PMU/PPMU), we do not have any abstract structure to represent them properly. 2. Such performance requirement devices (PMU/PPMU) are actual hardware pieces that may be represented by Device Tree directly while devfreq device itself is a virtual entity that are not considered to be represented by Device Tree according to Device Tree folks. In order to address such issues, a devferq_event device (represented by this patch) provides a template for device drivers representing performance monitoring unit, which gives the basic or raw data for preformance requirement, which in turn, is required by devfreq governors. The following description explains the feature of two kind of devfreq class: - devfreq class (existing) : devfreq consumer device use raw data from devfreq_event device for determining proper current system state and change voltage/frequency dynamically using various governors. - devfreq_event class (new) : Provide measured raw data to devfreq device for governor Cc: MyungJoo Ham <myungjoo.ham@samsung.com> Cc: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com> [Commit message rewritten & conflict resolved by MyungJoo] Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2015-01-29PM / devfreq: tegra: add devfreq driver for Tegra Activity MonitorTomeu Vizoso
The ACTMON block can monitor several counters, providing averaging and firing interrupts based on watermarking configuration. This implementation monitors the MCALL and MCCPU counters to choose an appropriate frequency for the external memory clock. This patch is based on work by Alex Frid <afrid@nvidia.com> and Mikko Perttunen <mikko.perttunen@kapsi.fi>. Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2015-01-06rcu: Make SRCU optional by using CONFIG_SRCUPranith Kumar
SRCU is not necessary to be compiled by default in all cases. For tinification efforts not compiling SRCU unless necessary is desirable. The current patch tries to make compiling SRCU optional by introducing a new Kconfig option CONFIG_SRCU which is selected when any of the components making use of SRCU are selected. If we do not select CONFIG_SRCU, srcu.o will not be compiled at all. text data bss dec hex filename 2007 0 0 2007 7d7 kernel/rcu/srcu.o Size of arch/powerpc/boot/zImage changes from text data bss dec hex filename 831552 64180 23944 919676 e087c arch/powerpc/boot/zImage : before 829504 64180 23952 917636 e0084 arch/powerpc/boot/zImage : after so the savings are about ~2000 bytes. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com> CC: Josh Triplett <josh@joshtriplett.org> CC: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: resolve conflict due to removal of arch/ia64/kvm/Kconfig. ]
2014-09-29PM / devfreq: exynos: Enable building exynos PPMU as modulePunit Agrawal
Export symbols from the PPMU driver needed to build the exynos bus driver as a module. Cc: MyungJoo Ham <myungjoo.ham@samsung.com> Cc: Kyungmin Park <kyungmin.park@samsung.com> Cc: Kukjin Kim <kgene.kim@samsung.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2014-09-29PM / devfreq: Remove ARCH_HAS_OPP completelyPaul Bolle
The Kconfig symbol ARCH_HAS_OPP became redundant in v3.16: commit 049d595a4db3 ("PM / OPP: Make OPP invisible to users in Kconfig") removed the only dependency that used it. Setting it had no effect anymore. So commit 78c5e0bb145d ("PM / OPP: Remove ARCH_HAS_OPP") removed it. For some reason that commit did not remove all select statements for that symbol. These statements are now useless. Remove one from devfreq too. Signed-off-by: Paul Bolle <pebolle@tiscali.nl> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2014-07-23PM / OPP: Remove ARCH_HAS_OPPMark Brown
Since the OPP layer is a kernel library which has been converted to be directly selectable by its callers rather than user selectable and requiring architectures to enable it explicitly the ARCH_HAS_OPP symbol has become redundant and can be removed. Do so. Signed-off-by: Mark Brown <broonie@linaro.org> Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Nishanth Menon <nm@ti.com> Acked-by: Rob Herring <robh@kernel.org> Acked-by: Shawn Guo <shawn.guo@freescale.com> Acked-by: Simon Horman <horms+renesas@verge.net.au> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-05-24PM / devfreq: remove checks for CONFIG_EXYNOS_ASVPaul Bolle
Checks for CONFIG_EXYNOS_ASV were added in v3.3. But the related Kconfig symbol has never been added to the tree. Remove these checks, as they always evaluate to false. Signed-off-by: Paul Bolle <pebolle@tiscali.nl> [Merge conflict resolved by MyungJoo] Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2014-05-24PM / devfreq: exynos5: Add CONFIG_PM_OPP dependency to fix probe failChanwoo Choi
This patch add CONFIG_PM_OPP dependecy to exynos5_bus driver to fix probe fail. If CONFIG_PM_OPP is disabled, dev_pm_opp_find_freq_floor() will always return ERR_PTR(-EINVAL) error. Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com> Reviewed-by: Tomasz Figa <t.figa@samsung.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2014-05-24PM / devfreq: exynos4: Add CONFIG_PM_OPP dependency to fix probe failChanwoo Choi
This patch add CONFIG_PM_OPP dependecy to exynos4_bus driver to fix probe fail as following log: [ 3.721389] exynos4-busfreq busfreq.3: Fail to add opp entries. [ 3.721697] exynos4-busfreq: probe of busfreq.3 failed with error -22 If CONFIG_PM_OPP is disabled, dev_pm_opp_find_freq_floor() in xxx_probe() will always return -EINVAL error. Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com> Reviewed-by: Tomasz Figa <t.figa@samsung.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2014-01-27PM / devfreq: Disable Exynos4 driver build on multiplatformSachin Kamat
Exynos4 devfreq driver uses mach/map.h which is not available on multiplatform. Hence disable build on multiplatform for now. Without this patch we get the following build errors: drivers/devfreq/exynos/exynos4_bus.h:15:22: fatal error: mach/map.h: No such file or directory Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2013-06-03PM / devfreq: fix typo "CPU_EXYNOS4.12" twicePaul Bolle
Dependencies on CPU_EXYNOS4212 and CPU_EXYNOS4412 for the "ARM Exynos4210/4212/4412 Memory Bus DEVFREQ Driver" were added in commit 7b4050381127ae11fcfc74a106d715a5fbbf888a ("PM/Devfreq: Add Exynos4-bus device DVFS driver for Exynos4210/4212/4412."). The tree (at that time, v3.3, and currently) makes clear that this should have been dependencies on SOC_EXYNOS4212 and SOC_EXYNOS4412. Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
2013-06-03PM / devfreq: Add Exynos5-bus devfreq driver for Exynos5250Abhilash Kesavan
Exynos5-bus device devfreq driver monitors PPMU counters and adjusts operating frequencies and voltages with OPP. ASV should be used to provide appropriate voltages as per the speed group of the SoC rather than using a constant 1.025V. Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com> [myungjoo.ham@samsung.com: minor style update] Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Cc: Jonghwan Choi <jhbird.choi@samsung.com> Cc: Kukjin Kim <kgene.kim@samsung.com>
2012-11-20PM / devfreq: governors: add GPL module license and allow module buildNishanth Menon
Add GPL module license and remove the static build restrictions for building governors. This allows governors now to be loaded on a need basis and reloaded independently of kernel build Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org> Cc: MyungJoo Ham <myungjoo.ham@samsung.com> Cc: Kyungmin Park <kyungmin.park@samsung.com> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Kevin Hilman <khilman@ti.com> Cc: linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Nishanth Menon <nm@ti.com> Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2012-04-16Fix typo in various Kconfig fileMasanari Iida
Correct spelling typo in various Kconfig file. Signed-off-by: Masanari Iida <standby24x7@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2011-12-20PM/Devfreq: Add Exynos4-bus device DVFS driver for Exynos4210/4212/4412.MyungJoo Ham
Exynos4-bus device devfreq driver add DVFS capability for Exynos4210/4212/4412-Bus (memory). The driver monitors PPMU counters of memory controllers and adjusts operating frequencies and voltages with OPP. For Exynos4210, vdd_int is controlled. For exynos4412/4212, vdd_mif and vdd_int are controlled. Dependency (CONFIG_EXYNOS_ASV): Exynos4 ASV driver has been posted in the mailing list; however, it si not yet upstreamed. Although the current revision of Exynos4 ASV patch does not contain "CONFIG_EXYNOS_ASV", we have added the symbol to hide the dependent from compilers for now. As soon as Exynos4 ASV drivers are merged, the #ifdef statement will be removed or the name will be changed. However, enabling ASV is essential in most Exynos4 chips to reduce the power consumption of Exynos4210 because without ASV, this Devfreq driver assumes the worst case scenario, which consumes more power. Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> --- Changes from v1 - Support 4212 and 4412 as well as 4210.
2011-11-14PM / devfreq: correct Kconfig dependencyMyungJoo Ham
Devfreq does not depend on OPP. The dependency is removed. Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-10-02PM / devfreq: Add basic governorsMyungJoo Ham
Four cpufreq-like governors are provided as examples. powersave: use the lowest frequency possible. The user (device) should set the polling_ms as 0 because polling is useless for this governor. performance: use the highest freqeuncy possible. The user (device) should set the polling_ms as 0 because polling is useless for this governor. userspace: use the user specified frequency stored at devfreq.user_set_freq. With sysfs support in the following patch, a user may set the value with the sysfs interface. simple_ondemand: simplified version of cpufreq's ondemand governor. When a user updates OPP entries (enable/disable/add), OPP framework automatically notifies devfreq to update operating frequency accordingly. Thus, devfreq users (device drivers) do not need to update devfreq manually with OPP entry updates or set polling_ms for powersave , performance, userspace, or any other "static" governors. Note that these are given only as basic examples for governors and any devices with devfreq may implement their own governors with the drivers and use them. Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Reviewed-by: Mike Turquette <mturquette@ti.com> Acked-by: Kevin Hilman <khilman@ti.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-10-02PM: Introduce devfreq: generic DVFS framework with device-specific OPPsMyungJoo Ham
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@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Reviewed-by: Mike Turquette <mturquette@ti.com> Acked-by: Kevin Hilman <khilman@ti.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>