Hi Lyude,
On 3/7/20 12:54 AM, Lyude Paul wrote:
On Wed, 2020-02-26 at 18:52 +0100, Hans de Goede wrote:
Hi,
On 2/26/20 5:05 PM, Alex Deucher wrote:
On Wed, Feb 26, 2020 at 10:43 AM Hans de Goede <hdegoede@xxxxxxxxxx>
wrote:
Hi,
On 2/26/20 4:29 PM, Alex Deucher wrote:
On Wed, Feb 26, 2020 at 10:16 AM Hans de Goede <hdegoede@xxxxxxxxxx>
wrote:
Hi Lyude and everyone else,
Lyude I'm mailing you about this because you have done a lot of
work on DP MST, but if this rings a bell to anyone else feel
free to weigh in on this.
Might be a duplicate of:
https://gitlab.freedesktop.org/drm/amd/issues/1052
Looks like you are right, reverting the commit which the bisect
from that issue points to:
cd82d82cbc04 ("drm/dp_mst: Add branch bandwidth validation to MST atomic
check")
Fixes the issue for me. I will add a comment to the issue.
Note I'm using integrated Intel gfx, so that means that this issue
definitely is not amdgpu specific.
I'm not too familiar with the mst code, but I wonder if we were
exceeding the bandwidth limits in some setups and it just happened to
work, but now that we enforcing them, they don't which is correct, but
a regression from some users' perspective?
I seriously doubt that is the case according to:
https://support.lenovo.com/nl/en/solutions/pd029622
The gen 2 tb3 dock can handle 2 external
displays at 3840*2160@60Hz together with the internal
panel being on and both my external displays run at
1920x1080@60 so I'm consuming less then half of the
maximum bandwidth.
OK-so I wasn't actually able to reproduce this issue with my setup (I've got a
X1 Carbon 7th generation, but I don't have the 2nd generation dock - only the
first generation dock) but I'm certain I've actually fixed it now, since I
realized we did not have a very good understanding of how PBN limitations are
advertised with MST. I rewrote the bandwidth checks again, and in the process
also found a much more subtle regression that got introduced in 5.6, which
would sometimes cause MST probing to appear to just stop in it's tracks with
no messages.
I cc'd both patch series to you, so I'd recommend applying them both onto your
kernel and seeing if that fixes your issues. If it still doesn't, then get me
some kernel logs with:
drm.debug=0x116 log_buf_len=50M
And I'll take a closer look. I'm pretty confident this should fix everything
though :)
I can confirm that the v2 series you posted fixes the problem of only of the 2
FHD monitors on my Lenovo TB3 gen 2 dock lighting up, thank you!
Regards,
Hans
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