fa3cdf8d0b
When probing a new MST device, it's not safe to make any assumptions about it's current state. While most well mannered MST hubs will just disable the branching unit on hotplug disconnects, this isn't enough to save us from various other scenarios that might have resulted in something writing to the MST branching unit before we got control of it. This could happen if a previous probe we tried failed, if we're booting in kexec context and the hub is still in the state the last kernel put it in, etc. Luckily; there is no reason we can't just reset the branching unit every time we enable a new topology. So, fix this by resetting it on enabling new topologies to ensure that we always start off with a clean, unmodified topology state on MST sinks. This fixes occasional hard-lockups on my P50's laptop dock (e.g. AUX times out all DPCD trasactions) observed after multiple docks, undocks, and module reloads. Signed-off-by: Lyude Paul <lyude@redhat.com> Cc: stable@vger.kernel.org Cc: Karol Herbst <karolherbst@gmail.com> Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.