On Thu, Jun 03, 2021 at 03:15:05PM +0200, Maciej W. Rozycki wrote:

 I have lost track about this issue, so please fill me in as to whether 
the offending commit causing the regression has been bisected or not.

It has.  Michael Cree reported the following back on April 5th:

And the first bad commit is:

0fe3cf3a53b5c1205ec7d321be1185b075dff205 is the first bad commit
commit 0fe3cf3a53b5c1205ec7d321be1185b075dff205
Author: Christian König [off-list ref]
Date:   Sat Oct 24 13:12:23 2020 +0200

    drm/radeon: switch to new allocator v2
    
    It should be able to handle all cases here.
    
    v2: fix debugfs as well
    
    Signed-off-by: Christian König [off-list ref]
    Reviewed-by: Dave Airlie [off-list ref]
    Reviewed-by: Madhav Chauhan [off-list ref]
    Tested-by: Huang Rui [off-list ref]
    Link: https://patchwork.freedesktop.org/patch/397088/?series=83051&rev=1

:040000 040000 4e643ef861b921392bc67be21a42298c91c7ff7a b36453567c3176a3cd50fa0b23886b0fd642560d M	drivers

--Bob