[DC] - Maximum pixel clock of dual-link DVI too low for some modes

Submitted by aqxa1 @aqxa1

Assigned to Default DRI bug account

Link to original bug (#105302)

Description

I have a monitor that supports 2560x1440 >60hz (up to around 110hz) through the DVI-D interface but requires pixel clocks greater than the current dual-link limit of 330khz, with amdgpu.dc=1. Setting TMDS_MAX_PIXEL_CLOCK to 250000 in signal_types.h works around the problem.

amdgpu.dc=0 doesn't appear to have this limit (or the value is higher) so the problem does not exist there.

I'm using ~ag5df's drm-next-4.17-wip branch.

There appears to be a discussion about setting a higher pixel clock limit in this bug: https://bugs.freedesktop.org/show_bug.cgi?id=93885 but focused on HDMI and not DVI-D, and regarding the older radeon driver.