Re: [PATCH] thunderbolt: Assert downstream port reset on shutdown

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Tue, Jun 09, 2026 at 01:25:55AM -0500, Basavaraj Natikar wrote:
> 
> On 6/8/2026 10:25 AM, Mario Limonciello wrote:
> > > > 
> > > > I guess I see two approaches.
> > > > 
> > > > 1) Move to shutdown only (your suggestion).
> > > > 
> > > > Corner case of user who unloads before shutdown means they could
> > > > be exposed
> > > > to this.
> > > > 
> > > > 2) Link the DPR behavior to host_reset module behavior.
> > > > 
> > > > IE If a user set host_reset=0 avoid host reset on module load
> > > > and avoid DPR
> > > > on module unload/shutdown.
> > > > 
> > > > If user kept host_reset=1 then do DPR on unload.
> > > > 
> > > > Always do on shutdown (regardless of host_reset value).
> > > > 
> > > > What do you think of #2?
> > > 
> > > That sounds better. Also we could restrict this more for links that
> > > are TB3
> > > e.g no need to do for USB4, assuming that is simple to do.
> > 
> > OK thanks.  Basavaraj, thoughts?
> > 
> > The way that this was found was by looking at the traces of what Windows
> > and Linux were doing differently at shutdown.
> > 
> > Maybe before we make a decision to tie it only to TBT3 we should double
> > check if Windows was also doing the DPR for USB4 too.
> 
> So the traces confirm Windows only asserts DPR for TB3 and not for USB4
> docks, which matches what Mika suggested. For v2 I will restrict the
> reset to legacy TB3 devices (skip USB4 routers) and fold in the
> host_reset changes (the second approach).

Sounds good to me.