AMD A6-4455M APU with Radeon(tm) HD Graphics in 50% leads to a black screen when starting X

[Alexey Dokuchaev]

On Mon, Apr 27, 2020 at 05:33:31PM +0200, thorsten.johannvorderbrueggen at t-online.de wrote:
> Hi @all,
> 
> i have a [AMD A6-4455M based] Samsung NP535U3C-A02DE Laptop and i
> installed FreeBSD 12.1 on it ... so far so good :-) ... before that i
> had void-linux on it ... it worked with any trouble ... especially X
> 
> With FreeBSD i have a 50/50 chance to get a black screen at the end...
> the sytems starts ... loader starts ... the kernel starts ... it
> detects drm and so but then it switches the resolution to 1366x768 ...
> this takes some time (10-15 sec)

I'm having similar issues with A8-5550M, none of the drm-* ports work
reliably on it.  It usually locks up with black screen, or even if it
manages to load, X.Org falls back to software rendering.

> [drm:r600_ring_test] radeon: ring 0 test failed (scratch(0x8504)=0xCAFEDEAD)
> [drm:cayman_resume] cayman startup failed on resume
> [drm:radeon_dp_link_train_cr] displayport link status failed
> [drm:radeon_dp_link_train_cr] clock recovery failed
> drmn0: ring 0 stalled for more than 10495msec
> drmn0: GPU lockup (current fence id 0x0000000000000001 last fence id 0x0000000000000002 on ring 0)
> drmn0: ring 0 stalled for more than 11026msec

I believe these "stalled" lines are related to the 10-20 seconds delay
during initialization.  Something got broken in Northern Islands cards
support in recent years, it was definitely working two or three years
ago (fast module loading, no crashes, hw-accelerated rendering).  I'm
slowly bisecting and trying different versions of the DRM ports, but
that can take months...  I have no good news or answers at this moment.

/danfe