Re: [PATCH v4] thunderbolt: Disable Gen 4 Recovery on Asymmetric Transitions

Mika Westerberg
2025-02-03T12:59:21Z

On Mon, Feb 03, 2025 at 12:43:04PM +0000, Mohammad Rahimi wrote:
> Hello again.
>
> On Mon, Feb 03, 2025 at 02:39:44PM GMT, Mika Westerberg wrote:
> > Hi,
> >
> > On Mon, Feb 03, 2025 at 12:25:21PM +0000, Mohammad Rahimi wrote:
> > > Hello.
> > >
> > > On Mon, Feb 03, 2025 at 10:42:24AM GMT, Mika Westerberg wrote:
> > > > Hi,
> > > >
> > > > On Fri, Jan 31, 2025 at 01:41:27AM +0000, Mohammad Rahimi wrote:
> > > > > Updates the Connection Manager to disable the Gen 4 Link Recovery
> > > > > flow before transitioning from a Symmetric Link to an Asymmetric
> > > > > Link, as specified in recent changes to the USB4 v2 specification.
> > > > >
> > > > > According to the "USB4 2.0 ENGINEERING CHANGE NOTICE FORM"
> > > > > published in September 2024, the rationale for this change is:
> > > > >
> > > > > "Since the default value of the Target Asymmetric Link might be
> > > > > different than Symmetric Link and Gen 4 Link Recovery flow checks
> > > > > this field to make sure it matched the actual Negotiated Link Width,
> > > > > we’re removing the condition for a Disconnect in the Gen 4 Link
> > > > > Recovery flow when Target Asymmetric Link doesn’t match the actual
> > > > > Link width and adding a Connection Manager note to Disable Gen 4 Link
> > > > > Recovery flow before doing Asymmetric Transitions."
> > > > >
> > > > > Signed-off-by: Mohammad Rahimi <rahimi.mhmmd@gmail.com>
> > > >
> > > > I did some minor modifications and applied to thunderbolt.git/next. Please
> > > > let me know if I missed something.
> > > >
> > >
> > > Looks great. Just one question:
> > >
> > > In tb_configure_asym(), if tb_switch_set_link_width() fails, we won’t restore
> > > the link recovery status. Is that okay?
> >
> > Good question :) Looking at the ECR, does it actually say anywhere that the
> > CM should needs to re-enable it? I'm thinking that we could just disable it
> > and be done with it?
>
> Right. Thanks for clearing that up.

I'll check with the HW/FW folks still if they have any suggestions. I'll
keep you updated.