Thanks! Filed a bug for it now: https://gitlab.freedesktop.org/drm/amd/-/issues/4756
On Fri, 5 Dec 2025 at 18:00, Natalie Klestrup Röijezon <[email protected]> wrote: > > > ________________________________ > From: Alex Hung <[email protected]> > Sent: Friday, December 5, 2025 17:45 > To: Natalie Klestrup Röijezon <[email protected]>; > [email protected] <[email protected]> > Subject: Re: linux-stable 6.17.10 (and 6.18.0) regression - broken > DisplayPort MST/daisy chaining > > Hi, > > Can you file a bug to https://gitlab.freedesktop.org/drm/amd/-/issues/ > so it's easier to track this issue later? Thanks. > > I will forward this to patch author at the same time. > > > On 12/5/25 07:26, Natalie Klestrup Röijezon wrote: > > Hey, > > > > After upgrading to Linux 6.18.0 I noticed that my daisy-chained display > > setup (Lenovo ThinkPad P16s Gen 4 AMD feeding 3x Dell U2424HE monitors > > over USB-C for the first, and then daisy-chained MST between them for > > the rest, running at 1080p@120Hz) would no longer work: > > displays 2 and 3 in the chain would just show "no DP signal" errors > > instead. > > > > The same problem also happens on 6.17.10, but 6.17.9 is fine. > > > > I bisected it down to > > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c?h=v6.17.10&id=18030e84cbda014787369b6d4cde8404fa2d08fc > > and have confirmed that it 6.17.10 with > > 18030e84cbda014787369b6d4cde8404fa2d08fc reverted runs fine again, > > and is able to feed all three monitors. > > > > Now, obviously the patch exists for a /reason/, but at the moment it > > appears to just be trading one miscalculation for another.. would it make > > sense to revert it for now? > > > > Happy to (try to) assist in troubleshooting, but I'm also woefully > > underinformed about what the numbers are supposed to be instead. > > > > Thanks, > > Natalie Klestrup Röijezon >
