구차니의 잡동사니 모음

    //

    // The I2C0 peripheral must be enabled before use.

    //

    SysCtlPeripheralEnable(SYSCTL_PERIPH_I2C0);

    //

    // For this example I2C0 is used with PortB[3:2].  The actual port and

    // pins used may be different on your part, consult the data sheet for

    // more information.  GPIO port B needs to be enabled so these pins can

    // be used.

    // TODO: change this to whichever GPIO port you are using.

    //

    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);

    //

    // Configure the pin muxing for I2C0 functions on port B2 and B3.

    // This step is not necessary if your part does not support pin muxing.

    // TODO: change this to select the port/pin you are using.

    //

    GPIOPinConfigure(GPIO_PB2_I2C0SCL);

    GPIOPinConfigure(GPIO_PB3_I2C0SDA);

    //

    // Select the I2C function for these pins.  This function will also

    // configure the GPIO pins pins for I2C operation, setting them to

    // open-drain operation with weak pull-ups.  Consult the data sheet

    // to see which functions are allocated per pin.

    // TODO: change this to select the port/pin you are using.

    //

    GPIOPinTypeI2CSCL(GPIO_PORTB_BASE, GPIO_PIN_2);

    GPIOPinTypeI2C(GPIO_PORTB_BASE, GPIO_PIN_3); 

$ cat /etc/init.d/cpufrequtils

#!/bin/sh

### BEGIN INIT INFO

# Provides:       cpufrequtils

# Required-Start: $remote_fs loadcpufreq

# Required-Stop:

# Default-Start:  2 3 4 5

# Default-Stop:

# Short-Description: set CPUFreq kernel parameters

# Description: utilities to deal with CPUFreq Linux

#       kernel support

### END INIT INFO

#

DESC="CPUFreq Utilities"

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

CPUFREQ_SET=/usr/bin/cpufreq-set

CPUFREQ_INFO=/usr/bin/cpufreq-info

CPUFREQ_OPTIONS=""

# use lsb-base

. /lib/lsb/init-functions

# Which governor to use. Must be one of the governors listed in:

#   cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors

#

# and which limits to set. Both MIN_SPEED and MAX_SPEED must be values

# listed in:

#   cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies

# a value of 0 for any of the two variables will disabling the use of

# that limit variable.

#

# WARNING: the correct kernel module must already be loaded or compiled in.

#

# Set ENABLE to "true" to let the script run at boot time.

#

# eg:   ENABLE="true"

#       GOVERNOR="ondemand"

#       MAX_SPEED=1000

#       MIN_SPEED=500

ENABLE="true"

GOVERNOR="ondemand"

MAX_SPEED="0"

MIN_SPEED="0"

check_governor_avail() {

        info="/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors"

        if [ -f $info ] && grep -q "\<$GOVERNOR\>" $info ; then

                return 0;

        fi

        return 1;

}

[ -x $CPUFREQ_SET ] || exit 0

if [ -f /etc/default/cpufrequtils ] ; then

        . /etc/default/cpufrequtils

fi

# if not enabled then exit gracefully

[ "$ENABLE" = "true" ] || exit 0

if [ -n "$MAX_SPEED" ] && [ $MAX_SPEED != "0" ] ; then

        CPUFREQ_OPTIONS="$CPUFREQ_OPTIONS --max $MAX_SPEED"

fi

if [ -n "$MIN_SPEED" ] && [ $MIN_SPEED != "0" ] ; then

        CPUFREQ_OPTIONS="$CPUFREQ_OPTIONS --min $MIN_SPEED"

fi

if [ -n "$GOVERNOR" ] ; then

        CPUFREQ_OPTIONS="$CPUFREQ_OPTIONS --governor $GOVERNOR"

fi

CPUS=$(cat /proc/stat|sed -ne 's/^cpu\([[:digit:]]\+\).*/\1/p')

RETVAL=0

case "$1" in

        start|force-reload|restart|reload)

                log_action_begin_msg "$DESC: Setting $GOVERNOR CPUFreq governor"

                if check_governor_avail ; then

                        for cpu in $CPUS ; do

                                log_action_cont_msg "CPU${cpu}"

                                $CPUFREQ_SET --cpu $cpu $CPUFREQ_OPTIONS 2>&1 > /dev/null || \

                                        RETVAL=$?

                        done

                        log_action_end_msg $RETVAL ""

                else

                        log_action_cont_msg "disabled, governor not available"

                        log_action_end_msg $RETVAL

                fi

                ;;

        stop)

                ;;

        *)

                echo "Usage: $0 {start|stop|restart|reload|force-reload}"

                exit 1

esac

exit 0 

$ cpufreq-info

cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009

Report errors and bugs to cpufreq@vger.kernel.org, please.

analyzing CPU 0:

  driver: BCM2835 CPUFreq

  CPUs which run at the same hardware frequency: 0 1 2 3

  CPUs which need to have their frequency coordinated by software: 0 1 2 3

  maximum transition latency: 355 us.

  hardware limits: 600 MHz - 900 MHz

  available frequency steps: 600 MHz, 900 MHz

  available cpufreq governors: conservative, ondemand, userspace, powersave, performance

  current policy: frequency should be within 600 MHz and 900 MHz.

                  The governor "ondemand" may decide which speed to use

                  within this range.

  current CPU frequency is 600 MHz.

  cpufreq stats: 600 MHz:52.90%, 900 MHz:47.10%  (9)

$ sudo cpufreq-set -g conservative

$ cpufreq-info

cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009

Report errors and bugs to cpufreq@vger.kernel.org, please.

analyzing CPU 0:

  driver: BCM2835 CPUFreq

  CPUs which run at the same hardware frequency: 0 1 2 3

  CPUs which need to have their frequency coordinated by software: 0 1 2 3

  maximum transition latency: 355 us.

  hardware limits: 600 MHz - 900 MHz

  available frequency steps: 600 MHz, 900 MHz

  available cpufreq governors: conservative, ondemand, userspace, powersave, performance

  current policy: frequency should be within 600 MHz and 900 MHz.

                  The governor "conservative" may decide which speed to use

                  within this range.

  current CPU frequency is 600 MHz.

  cpufreq stats: 600 MHz:63.64%, 900 MHz:36.36%  (15) 

$ sudo cpufreq-set -g powersave

$ cpufreq-info

cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009

Report errors and bugs to cpufreq@vger.kernel.org, please.

analyzing CPU 0:

  driver: BCM2835 CPUFreq

  CPUs which run at the same hardware frequency: 0 1 2 3

  CPUs which need to have their frequency coordinated by software: 0 1 2 3

  maximum transition latency: 355 us.

  hardware limits: 600 MHz - 900 MHz

  available frequency steps: 600 MHz, 900 MHz

  available cpufreq governors: conservative, ondemand, userspace, powersave, performance

  current policy: frequency should be within 600 MHz and 900 MHz.

                  The governor "powersave" may decide which speed to use

                  within this range.

  current CPU frequency is 600 MHz.

  cpufreq stats: 600 MHz:74.84%, 900 MHz:25.16%  (15)

$ sudo cpufreq-set -g performance

$ cpufreq-info

cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009

Report errors and bugs to cpufreq@vger.kernel.org, please.

analyzing CPU 0:

  driver: BCM2835 CPUFreq

  CPUs which run at the same hardware frequency: 0 1 2 3

  CPUs which need to have their frequency coordinated by software: 0 1 2 3

  maximum transition latency: 355 us.

  hardware limits: 600 MHz - 900 MHz

  available frequency steps: 600 MHz, 900 MHz

  available cpufreq governors: conservative, ondemand, userspace, powersave, performance

  current policy: frequency should be within 600 MHz and 900 MHz.

                  The governor "performance" may decide which speed to use

                  within this range.

  current CPU frequency is 900 MHz.

  cpufreq stats: 600 MHz:79.71%, 900 MHz:20.29%  (16)

1. Ondemand

이건 다들 알거라 생각합니다. 이가버저의 특징은 수요에 따라 클럭을 조절한다는거죠.수요가 높으면 클럭을 올리고 수요가 낮으면

클럭을 낮추고 이렇기 때문에 베터리 효율도 높고 성능도 무난하게 뽑아줘서 안드로이드 대부분의 기기의 기본 가버너로 설정되어있습니다.(갤넥같은경우 인터렉티브가 기본이더군요;;) 이 가버너는 xda에서 유명한 커널중 하나인 트리니티 커널에서도의 기본가버너로 설정되어있다고 하네요.

8. Pegasusq

ondemand기반으로 만들어진 가버너입니다. 그런데 이 가버너는 특이하게 클럭조절을 

중간클럭까지 골고루 섞어쓰기떄문에

저랑 한분이 한때 ondemand랑 interactive 이두개를놓고 서로 이기반이라 토론을 한적도 있습니다.

하지만 중간클럭을 쓰는건 ondemand에다가 hotplug를 섞었기 때문이라고 합니다. 

이 가버너가 생성된 배경은 코어가 4개나되는 쿼드코어 엑시노스를 풀가동 동기식으로했다간 폰베터리를 사살하는거밖에 안된다고 생각이든 삼성이 비동기식의 성질을 띄는hotplug를 섞어서 반비동기식형태로 제작하였습니다. 그래서 퍼포먼스와 배터리를 둘다잡은 가버너라 할수있지요. 그래서 요즘 대부분 커스텀 커널에는 듀얼코어용 pegasusq가버너를 추가하는 추세입니다.

하지만 엄연히 비동기식하고 틀립니다. 

참고로 이런성질때문에 싱글코어에서는 이가버너가

ondemand랑 똑같은 가버너가 되버리니 싱코에선 굳이 이 가버너를 채택할 필요는 없어보입니다.

11. Hotplug

이 가버너는 ondemand가버너와 매우 흡사한 가버너라고 합니다. 이 가버너 역시 또한 클럭수 요구에 따락 클럭을 올리고 내리고 한답니다. 하지만 다른가버너와 확연히 차이아는 차이점이있다면 바로 cpu부하가 매우적을때 (예로들어 대기모드일때) cpu하나를 꺼버린다고 합니다.

그래서 베터리를 아깐다고 하네요.

17. Conservative

이 가버너는 최대한 가능하면 저클럭에 머물려하고 하는 특징이 있다고 합니다. 다르게 표현을 하면 cpu가 클럭을 올리려면 계속 cpu에 부하를 줘야한다네요. 그리고 최소클럭을 사용자가 지정해줄경우 퍼포먼스가 떨어질 수 있다네요. 반대로 최소클럭을 내리면 베터리에는 좋다고 합니다.  

cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009

Report errors and bugs to cpufreq@vger.kernel.org, please.

analyzing CPU 0:

  driver: exynos_cpufreq

  CPUs which run at the same hardware frequency: 0

  CPUs which need to have their frequency coordinated by software: 0

  maximum transition latency: 11.0 us.

  hardware limits: 200 MHz - 2.00 GHz

  available frequency steps: 2.00 GHz, 1.92 GHz, 1.80 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.40 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz, 900 MHz, 80z

  available cpufreq governors: userspace, powersave, conservative, ondemand, performance

  current policy: frequency should be within 200 MHz and 1.60 GHz.

                  The governor "ondemand" may decide which speed to use

                  within this range.

  current CPU frequency is 200 MHz (asserted by call to hardware).

  cpufreq stats: 2.00 GHz:0.00%, 1.92 GHz:0.00%, 1.80 GHz:0.00%, 1.70 GHz:0.00%, 1.60 GHz:99.54%, 1.50 GHz:0.00%, 1.40 GHz:0.00%, 1.30 GHz:0.00%, 1.20) 

$ sudo vi /etc/smsc95xx_mac_addr 

$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors

performance