Supported Video Resolutions for Mainline Linux
For support of video resolutions in mainline Linux, the most updated source can be found here: https://github.com/libre-computer-project/libretech-linux/blob/linux-4.14/libretech-cc-master-stable/drivers/gpu/drm/meson/meson_dw_hdmi.c
We handle the following features
- HPD Rise & Fall interrupt
- HDMI Controller Interrupt
- HDMI PHY Init for 480i to 1080p60
- VENC & HDMI Clock setup for 480i to 1080p60
- VENC Mode setup for 480i to 1080p60
What is missing :
- PHY, Clock and Mode setup for 2k && 4k modes
- SDDC Scrambling mode for HDMI 2.0a
- HDCP Setup
- CEC Management
If you find that your video resolution isn't supported, you can try to get the frequency of the resolution and trying to add that frequency to the "switch (vclk_freq)" block of the file above and recompiling the kernel. After confirming it works with your monitor setup, please let us know and we can try to add it for future images.
You can find the frequencies by typing
sudo journalctl --no-pager | grep Modeline. The frequency is the number after the resolution.
/usr/lib/gdm3/gdm-x-session: (II) modeset(0): Modeline "3840x2160"x0.0 297.00 3840 4016 4104 4400 2160 2168 2178 2250 +hsync +vsync (67.5 kHz eP)
Frequency is indicated by 297.00 which is 297000. However per the above, the PHY, Clock, and Mode setup for 2K+ resolutions are not yet supported by the rest of the code.