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

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Date:   Mon, 5 Jun 2023 11:24:12 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     neil.armstrong@...aro.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] usb: typec: add support for the nb7vpq904m Type-C
 Linear Redriver

Hi Neil,

On Thu, Jun 01, 2023 at 11:21:13AM +0200, neil.armstrong@...aro.org wrote:
> From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> 
> 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@...aro.org>
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---
>  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).

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"?).

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.

thanks,

-- 
heikki

View attachment "redriver_device_type.diff" of type "text/plain" (3016 bytes)