[RFC PATCHv2 0/7] devfreq: Add devfreq-event class to provide raw data for devfreq device

Chanwoo Choi
2014-12-09T14:13:19Z

This patchset add new devfreq_event class to provide raw data to determine
current utilization of device which is used for devfreq governor.

[Description of devfreq-event class]
This patchset add new devfreq_event class for devfreq_event device which provide
raw data (e.g., memory bus utilization/GPU utilization). This raw data from
devfreq_event data would be used for the governor of devfreq subsystem.
- devfreq_event device : Provide raw data for governor of existing devfreq device
- devfreq device : Monitor device state and change frequency/voltage of device
using the raw data from devfreq_event device

The devfreq subsystem support generic DVFS(Dynamic Voltage/Frequency Scaling)
for Non-CPU Devices. The devfreq device would dertermine current device state
using various governor (e.g., ondemand, performance, powersave). After completed
determination of system state, devfreq device would change the frequency/voltage
of devfreq device according to the result of governor.

But, devfreq governor must need basic data which indicates current device state.
Existing devfreq subsystem only consider devfreq device which check current system
state and determine proper system state using basic data. There is no subsystem
for device providing basic data to devfreq device.

The devfreq subsystem must need devfreq_event device(data-provider device) for
existing devfreq device. So, this patch add new devfreq_event class for
devfreq_event device which read various basic data(e.g, memory bus utilization,
GPU utilization) and provide measured data to existing devfreq device through
standard APIs of devfreq_event class.

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

Also, the devfreq-event device would support various type event as following:
: DEVFREQ_EVENT_TYPE_RAW_DATA
: DEVFREQ_EVENT_TYPE_UTILIZATION
: DEVFREQ_EVENT_TYPE_BANDWIDTH
: DEVFREQ_EVENT_TYPE_LATENCY

[For example]
If board dts includes PPMU_DMC0/DMC1/CPU event node,
would show following sysfs entry. Also devfreq driver(e.g., exynos4_bus.c)
can get the instance of devfreq-event device by using provided API and then
get raw data which reflect the current state of device.

-sh-3.2# pwd
/sys/class/devfreq_event
-sh-3.2# ls -al
total 0
drwxr-xr-x 2 root root 0 Jan 7 11:10 .
drwxr-xr-x 37 root root 0 Jan 7 11:10 ..
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.0 -> ../../devices/soc/106a0000.ppmu_dmc0/devfreq_event/event.0
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.1 -> ../../devices/soc/106a0000.ppmu_dmc0/devfreq_event/event.1
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.2 -> ../../devices/soc/106a0000.ppmu_dmc0/devfreq_event/event.2
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.3 -> ../../devices/soc/106a0000.ppmu_dmc0/devfreq_event/event.3
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.4 -> ../../devices/soc/106b0000.ppmu_dmc1/devfreq_event/event.4
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.5 -> ../../devices/soc/106c0000.ppmu_cpu/devfreq_event/event.5
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.6 -> ../../devices/soc/106c0000.ppmu_cpu/devfreq_event/event.6
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.7 -> ../../devices/soc/106c0000.ppmu_cpu/devfreq_event/event.7
lrwxrwxrwx 1 root root 0 Jan 7 11:10 event.8 -> ../../devices/soc/106c0000.ppmu_cpu/devfreq_event/event.8

Changes from v1:
- Code clean
- Add the description of devfreq-event structure
- Add 'is_enabled' function to devfreq_event_ops structure
- Add 'enable_count' field to devfreq_event_dev structure
- Check whether devfreq-event device is enabled or not
during calling devfreq_event API
- Define the type of devfreq-event device as following
: DEVFREQ_EVENT_TYPE_RAW_DATA
: DEVFREQ_EVENT_TYPE_UTILIZATION
: DEVFREQ_EVENT_TYPE_BANDWIDTH
: DEVFREQ_EVENT_TYPE_LATENCY
- Add the exclusive feature of devfreq-event device.
If devfreq-event device is used on only on devfreq driver,
should used 'devfreq_enable_event_dev_exclusive()' function
- Add new patch6 for test on Exynos3250-based Rinato board

Chanwoo Choi (7):
devfreq: event: Add new devfreq_event class to provide basic data for devfreq governor
devfreq: event: Add the list of supported devfreq-event type
devfreq: event: Add the exclusive flag for devfreq-event device
devfreq: event: Add exynos-ppmu devfreq event driver
ARM: dts: Add PPMU dt node for Exynos3250
ARM: dts: Add PPMU dt node for Exynos4 SoC
ARM: dts: exynos: Add PPMU dt node to Exynos3250-based Rinato board

arch/arm/boot/dts/exynos3250-rinato.dts | 55 +++++
arch/arm/boot/dts/exynos3250.dtsi | 66 ++++++
arch/arm/boot/dts/exynos4.dtsi | 96 ++++++++
arch/arm/boot/dts/exynos4210.dtsi | 8 +
drivers/devfreq/Kconfig | 11 +
drivers/devfreq/Makefile | 5 +-
drivers/devfreq/devfreq-event.c | 363 ++++++++++++++++++++++++++++
drivers/devfreq/event/Makefile | 2 +
drivers/devfreq/event/exynos-ppmu.c | 409 ++++++++++++++++++++++++++++++++
include/linux/devfreq.h | 178 ++++++++++++++
10 files changed, 1192 insertions(+), 1 deletion(-)
create mode 100644 drivers/devfreq/devfreq-event.c
create mode 100644 drivers/devfreq/event/Makefile
create mode 100644 drivers/devfreq/event/exynos-ppmu.c

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1.8.5.5