Dear Linux folks,
On the older MT8183 device Lenovo IdeaPad Duet Chromebook, running ChromeOS with their Linux 5.10.x, connecting a 1920x1080 Dell monitor to a USB-C adapter using HDMI, only the resolution of 1280x720 is configured, although the adapter also support 1920x1080. It happens with all adapters, for example, LMP USB-C mini Dock [1].
I reported it to the Chromium OS issue tracker [1], and the last comment is:
It seems the display pipeline for the internal display (DSI) has higher clock rate. Also, the resolution support depends on the refresh rate as well, so the claimed 2400x1080 might only work on lower refresh rate. For the external display, the display modes are mostly rejected by the pre-defined max_clock_khz in mtk_dpi.c: https://elixir.bootlin.com/linux/v6.11.4/source/drivers/gpu/drm/mediatek/mtk_dpi.c#L940
Can you confirm this? The font rendering seems not so good in the lower resolution, and strangely, playing movies these seem to be rendered in higher resolution (or the monitor or hardware does a good job in up-scaling).
Kind regards, Paul [1]: https://lmp-adapter.com/product/lmp-usb-c-mini-dock/ [2]: https://issuetracker.google.com/issues/295666708
