Re: [PATCH v4 0/3] Fix problems fetching TBT3 DROM from AMD USB4 routers

[Mika Westerberg]

Hi,

On Mon, Mar 06, 2023 at 03:14:07PM +0000, Limonciello, Mario wrote:
> [Public]
> 
> 
> 
> > -----Original Message-----
> > From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> > Sent: Monday, March 6, 2023 03:58
> > To: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> > Cc: linux-usb@xxxxxxxxxxxxxxx; Mehta, Sanju <Sanju.Mehta@xxxxxxx>;
> > linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: [PATCH v4 0/3] Fix problems fetching TBT3 DROM from AMD
> > USB4 routers
> > 
> > Hi Mario,
> > 
> > On Thu, Feb 23, 2023 at 03:07:40PM -0600, Mario Limonciello wrote:
> > > TBT3 devices when connected to an AMD USB4 router occasionally fail to
> > > properly respond to requests for the DROM via bit banging.
> > >
> > > Depending upon which part of the request failed will impact the severity.
> > > A number of workarounds have been put in place to let the driver handle
> > > the failed requests:
> > >
> > > commit e87491a9fd4e3 ("thunderbolt: Retry DROM reads for more failure
> > scenarios")
> > > commit a283de3ec646f ("thunderbolt: Do not resume routers if UID is not
> > set")
> > > commit 6915812bbd109 ("thunderbolt: Do not make DROM read success
> > compulsory")
> > > commit f022ff7bf377 ("thunderbolt: Retry DROM read once if parsing fails")
> > >
> > > Still even with these changes the failures do make it through. In comparing
> > > other CM implementations utilized on AMD systems, they all access the
> > > DROM directly from the NVM.
> > >
> > > To avoid triggering this issue, try to get the DROM directly from the NVM
> > > in Linux as well when devices have an LC.
> > >
> > > v4:
> > >  * Style fixups
> > >  * Fixup for wrong path for USB4 devices
> > >
> > > Mario Limonciello (3):
> > >   thunderbolt: Adjust how NVM reading works
> > >   thunderbolt: use `tb_eeprom_get_drom_offset` to discover DROM offset
> > >   thunderbolt: Refactor DROM reading
> > 
> > I split the device side into a separate function too, renamed root
> > switch to host router (as that's the correct USB4 term), and fixed a
> > couple style issues and applied to thunderbolt.git/next, thanks!
> > 
> > Please check that I did not mess up anything :)
> 
> They look good, thanks!

Thanks for checking!

> Would you consider to take 8d7f459107f74fbbdde3dd5b3874d2e748cb8a21 to
> the RC though, or would prefer to let it bake in next?

I would like to keep it too in next just to make sure nothing breaks
accidentally.