구차니의 잡동사니 모음

$ echo 11 > /sys/class/gpio/export 

$ echo out > /sys/class/gpio/gpio11/direction

$ echo 1 > /sys/class/gpio/gpio11/value

$ echo 0 > /sys/class/gpio/gpio11/value

$ echo 11 > /sys/class/gpio/unexport  

hdmi_group=2

hdmi_mode=87

hdmi_ignore_edid=0xa5000080

hdmi_cvt 3840 2160 15 

# replace N with the number of cores you want to keep using

maxcpus=N 

arm_freq Frequency of the ARM CPU in MHz. The default value is 700.

core_freq Frequency of the GPU processor core in MHz. It has an impact on CPU performance, since it drives the L2 cache. The default value is 250.

sdram_freq Frequency of the SDRAM in MHz. The default value is 400.

gpu_freq Sets core_freq, h264_freq, isp_freq, and  v3d_freq together. The default value is 250.

h264_freq Frequency of the hardware video block in MHz. The default value is 250.

isp_freq Frequency of the image sensor pipeline block in MHz. The default value is 250.

v3d_freq Frequency of the 3D block in MHz. The default value is 250.

arm_freq_min Minimum value of arm_freq used for dynamic frequency clocking. The default value is 700.

core_freq_min Minimum value of core_freq used for dynamic frequency clocking. The default value is 250.

sdram_freq_min Minimum value of sdram_freq used for dynamic frequency clocking. The default value is 400.

$ 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.

$ cat /boot/config.txt

#uncomment to overclock the arm. 700 MHz is the default.

#arm_freq=800

arm_freq_min=300

$ 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: 300 MHz - 900 MHz

  available frequency steps: 300 MHz, 900 MHz

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

  current policy: frequency should be within 300 MHz and 900 MHz.

                  The governor "ondemand" may decide which speed to use

                  within this range.

  current CPU frequency is 300 MHz.

  cpufreq stats: 300 MHz:16.33%, 900 MHz:83.67%  (7)

$ cat /boot/config.txt

arm_freq=600

arm_freq_min=100

$ 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: 100.0 MHz - 600 MHz

  available frequency steps: 100.0 MHz, 600 MHz

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

  current policy: frequency should be within 100.0 MHz and 600 MHz.

                  The governor "ondemand" may decide which speed to use

                  within this range.

  current CPU frequency is 600 MHz.

  cpufreq stats: 100.0 MHz:0.00%, 600 MHz:100.00%