On Fri, Oct 18, 2024 at 11:32 AM Geert Uytterhoeven
<geert+renesas@xxxxxxxxx> wrote:
> As I had to test Tomi's WIP patches to add mini-DP output support to
> Gray Hawk Single, I moved my (old and new) DisplayPort gear to my board
> farm, and thought this was a good opportunity to test mini-DP output on
> White Hawk as a baseline (CN5), and add support for the second mini-DP
> output on the White Hawk BreakOut board (CN15).
>
> For testing, I used the following hardware:
> (A) BenQ BL2420PT desktop display (2560x1440),
> (B) Joy-It Joy-View 15 portable display (1920x1080),
> (C) Lindy DisplayPort to 2 Port HDMI MST Hub,
> (D) Passive mini-DP to HDMI cable,
> (E) LogiLink Mini DisplayPort to VGA Converter.
>
> (A)-(C) are known to work with my Intel desktop.
> (D)-(E) are known to work with an old Dell XPS13.
>
> Software-wise, I used the frame buffer text console, "modetest -M
> rcar-du -s 86:1920x1080@XR24" or "modetest -M rcar-du -s
> 86:2560x1440@XR24", and fbtest.
>
> White Hawk CN5
> --------------
>
> 1. Mini-DP to (A) DP:
> - 2560x1440 works but flickers (flickering shifts image
> horizontally; perhaps a cable issue, as 2 below does work?)
> - 1920x1080 is stable
While I don't have a second Mini-DP-to-DP-M cable, I tried a few
other combos (now on Gray Hawk Single):
7. (D) + HDMI-F-F adapter + passive HDMI-F-to-DP-cable to (A) DP,
8. Mini-DP-to-DP-F cable (=X) + plain DP cable (=Y) to (A) DP,
unfortunately with the same results. Note that (X) is the same cable
as used in scenario 2 below, and (Y) works fine with my Intel desktop.
However, the maximum cable length for eDP seems to be 30 cm, so that
may explain why 2 below is the only wiring that works at 2560x1440
(despite cable (X) being 1m, i.e. still too long)?
> 2. Mini-DP to (C) to (A) HDMI:
> - 2560x1440 OK
> - 1920x1080 OK
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
