Krzysztof Kozlowski k kozlowski samsung com Samsung R amp D

Krzysztof Kozlowski K Kozlowski Samsung Com Samsung R Amp D-Free PDF

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Overview and goals,CPUfreq with clock down,Run time PM and power domains. SoC low power states,CPU idle drivers,Limit the consumption of energy by mobile device. Do not hurt performance at least to some extend,Target devices smartphones tablets wearables. Mobile devices are somehow different, Energy consumption is an important factor How often do you. have to charge your phone, Mobile device is mostly idle more opportunities to sleep.
The speech will focus on ARM architecture and,Samsung s Exynos System on Chip family although. ideas are not limited to Exynos,Mainline Linux kernel is changing very fast. Some details about specific kernel drivers may become. obsolete soon, Details as for current mainline kernel 3 16 and linux next. from August,All measurements were done on development devices. Custom kernels,Custom operating systems, They are not representative for market end products.
Sometimes measurements on these devices may not,be even close to market products. Many measurements were done in specific custom, configuration very different from market product e g. No CPU idle driver no CPUfreq driver,Booted to init bin sh. Measured on,Trats2 smartphone Exynos 4412 4 cores,freq 200 1400 MHz. Gear1 like wearable Exynos 4212 2 cores 200 1400 MHz. Exynos 3250 development board 2 cores 100 1000 MHz. Kernel used,Exynos 4212 and 4412 linux next next 20140804.
Exynos 3250 internal Linux kernel tree 3 10,Lack of full support in mainline. Ondemand governor adjusts the frequency and voltage. to current load,Specific conditions to embedded world one. frequency and voltage for whole cluster, On most SoCs one clock frequency voltage for all CPUs. Except big LITTLE e g 2 clusters on quad core Exynos Octa. Dual cluster SoCs have big LITTLE,CPUfreq driver,Photo by Pauli Rautakorpi. Separate CPUfreq drivers for each SoC,Moving toward one generic cpufreq cpu0 driver.
cpufreq cpu0 requires,Clock to operate on provided by clock driver. Optionally voltage regulator provided by regulator driver. Table of Operating Performance Points from Device Tree. OPP is a tuple of frequency and voltage,Clock regulator OPP frameworks add necessary. abstraction layer and make cpufreq cpu0 a generic,Reduces the frequency upon entering WFI or WFE. instruction Wait for Interrupt Event,All cores must be idle. Behaves like a hardware ondemand CPUfreq governor, But only for clock frequency voltages remain untouched.
Supported by most of Exynos SoCs, As part of clock driver for Exynos 3250 Exynos 4 and Exynos. Board SoC Frequency Idle mA Idle clock down,1400 198 170. Trats2 Exynos 4412,200 115 114,1400 102 82,Gear1 like Exynos 4212. 1000 36 2 26 7,Dev board Exynos 3250,100 19 2 18 5. Measurements in idle mode basic CPU idle WFI no load. No benefits if CPUfreq governor is ondemand which is quite obvious. ARMCLK cannot get below minimal frequency used in CPUfreq driver. Ondemand CPUfreq reduces also ARM voltage,ARMCLK clk down energy consumption.
current mA,Idle clock down, Putting devices into low power states when not used. Optionally automatically delayed suspends,Needs support in device drivers. Driver specifies when it is working and idle,Usage counter pm runtime get put. Time of last activities pm runtime mark last busy, Driver implements runtime suspend and resume callbacks. Local power control powered independently,Example power domains.
Multi Format Codec MFC,G3D e g Mali,Image Signal Processor. Linux offers a generic power domain framework 2,Used by SH Mobile and Exynos. Other vendors implement this on their own, Multiple Linux devices can be attached to a domain. Samsung s Exynos System on Chip family although ideas are not limited to Exynos Mainline Linux kernel is changing very fast Some details about specific kernel drivers may become obsolete soon Details as for current mainline kernel 3 16 and linux next from August All measurements were done on development devices Custom kernels Custom operating systems They are not representative for

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