Dual link DSI VBT packet issue with Apollolake
- Issue appears as only half of the display working correctly after boot, the other half stays blank. Reproduction rate is 100%.
- Occurs with Apollolake based Aava Mobile Inari10B tablets that have a dual link MIPI display requiring VBT packets to be sent on both ports
- Issue was first detected with Ubuntu Focal HWE 5.15.0-48 kernel, and reproduces also with drm-tip kernel build from drm-tip 2022-11-18 sources provided by Ubuntu (https://git.launchpad.net/~ubuntu-kernel-test/ubuntu/+source/linux/+git/mainline-crack/tag/?h=cod/mainline/cod/tip/drm-tip/2022-11-18)
- dmesg with "drm.debug=0xe log_buf_len=4M" from boot with Ubuntu drm-tip 2022-11-18 kernel is attached
- If https://patchwork.freedesktop.org/patch/486879/ is reverted, issue no longer occurs
Issue seems to be caused by intel_dsi_seq_port_to_port function checking for available ports indicated in intel_dsi->ports with port number when it should use port bitmask instead. Patch that has been tested to solve the issue with Ubuntu drm-tip 2022-11-18 kernel is attached.
0001-drm-i915-dsi-fix-VBT-send-packet-port-selection-for-.patch