Re: [PATCH 2/2] usb: typec: add support for the nb7vpq904m Type-C Linear Redriver

[neil . armstrong]

Hi,

On 05/06/2023 10:24, Heikki Krogerus wrote:
> Hi Neil,
>
> On Thu, Jun 01, 2023 at 11:21:13AM +0200, neil.armstrong@xxxxxxxxxx wrote:
> > From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> >
> > Add support for the ON Semiconductor NB7VPQ904M Type-C USB SuperSpeed
> > and DisplayPort ALT Mode Linear Redriver chip found on some devices
> > with a Type-C port.
> >
> > The redriver compensates ultra High-Speeed DisplayPort and USB
> > Super Speed signal integrity losses mainly due to PCB & transmission
> > cables.
> >
> > The redriver doesn't support SuperSpeed lines swapping, but
> > can support Type-C SBU lines swapping.
> >
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > Signed-off-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
> > ---
> >   drivers/usb/typec/mux/Kconfig      |   8 +
> >   drivers/usb/typec/mux/Makefile     |   1 +
> >   drivers/usb/typec/mux/nb7vpq904m.c | 526 +++++++++++++++++++++++++++++++++++++
> >   3 files changed, 535 insertions(+)
>
> This looks good to me, but I think you should register a retimer
> instead of a mode switch (the orientation switch is fine).

Indeed, I'm not familiar with namings but by looking around it seems that
redriver and retimers for USB-C applications are exactly the same.

> Retimers are handled just like the muxes, so this patch would not need
> that many changes, but you would need to change the first patch too.
> You would need to declare a "redriver-switch" instead of "mode-switch"
> property in your DT (or perhaps make it just "redriver" instead of
> "redriver-switch"?).

So it would need some additional handling to also set the retimer state
along the mux, but I was wondering, why having a separate handling
while the retimer state struct is exactly the same as the mux ?

> We just need to add a device type for redrivers to the retimer class -
> check the attached diff. Something like that.
>
> Let me know what you guys think.

I think I'll switch to retimer, thanks for pointing it to me...

Thanks,
Neil

> thanks,