7
VIA SOM-9X35-STK Yocto 3.1 EVK Quick Start Guide
3.4 DVFS
To verify the DVFS (Dynamic Voltage Frequency Scaling) function and list all the supported features, use the
following commands:
root@aiv8365m1v1-aiot-emmc:~# ls -al /sys/devices/system/cpu/cpu0/cpufreq/
total 0
drwxr-xr-x 4 root root 0 Aug 26 11:15 .
drwxr-xr-x 3 root root 0 Aug 26 11:15 ..
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 affected_cpus
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 cpuinfo_cur_freq
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 cpuinfo_max_freq
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 cpuinfo_min_freq
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 cpuinfo_transition_latency
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 related_cpus
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 scaling_available_frequencies
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 scaling_available_governors
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 scaling_cur_freq
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 scaling_driver
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 scaling_governor
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 scaling_max_freq
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 scaling_min_freq
-rwxr-xr-x 1 root root 4096 Aug 26 11:15 scaling_setspeed
drwxr-xr-x 2 root root 0 Aug 26 11:15 schedutil
drwxr-xr-x 2 root root 0 Aug 26 11:15 stats
To check the supported and current CPU frequency, use the following commands:
:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
850000 918000 987000 1056000 1125000 1216000 1308000 1400000 1466000 1533000 1633000 1700000
1767000 1834000 1917000 2001000
:~# cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
1308000
3.5
Display
There is no need to set the display device. If you connect an HDMI display, HDMI output will be automatically
enabled after booting. If you connect an LCD panel, LCD panel output will be automatically enabled after
booting.
To control the LCD backlight, use the following commands:
root@aiv8365m1v1-aiot-emmc:~# cd /sys/devices/platform/backlight_lcd0/backlight/backlight_
lcd0/
root@aiv8365m1v1-aiot-emmc:~# cat max_brightness
16
root@aiv8365m1v1-aiot-emmc:~# echo 16 > brightness
Note:
There are only 17 (0~16) levels for the LCD backlight control.
3.6
Video playback
The VIA SOM-9X35-STK supports H.265 and H.264 video decoding up to 1080p@60fps/40Mbps.
To playback video, use the following command:
root@aiv8365m1v1-aiot-emmc:~# gst-launch-1.0 -q playbin uri=file:/data/sda1/test.
mp4 flags=0x42 video-sink="mtkmdp width=640 height=480 ! video/x-raw,format=I420 !
mtkwaylandsink" audio-sink="autoaudiosink"
