linux-kernel - Re: [RFC PATCH 0/2] Add gpio-usb-c-connector compatible

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Message-ID: <CAA8EJpqx+VFW8z6oG=+pnhPN97Q3R6z+ygf85Uspve-9syQsUw@mail.gmail.com>
Date: Fri, 29 Mar 2024 14:53:42 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Krishna Kurapati <quic_kriskura@...cinc.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Rob Herring <robh@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Conor Dooley <conor+dt@...nel.org>, 
	Miquel Raynal <miquel.raynal@...tlin.com>, Guenter Roeck <linux@...ck-us.net>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Kyle Tso <kyletso@...gle.com>, 
	Fabrice Gasnier <fabrice.gasnier@...s.st.com>, 
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>, u.kleine-koenig@...gutronix.de, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, devicetree@...r.kernel.org, 
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
	quic_ppratap@...cinc.com, quic_jackp@...cinc.com
Subject: Re: [RFC PATCH 0/2] Add gpio-usb-c-connector compatible

On Fri, 29 Mar 2024 at 09:20, Krishna Kurapati
<quic_kriskura@...cinc.com> wrote:
>
> QDU1000 IDP [1] has a Type-c connector and supports USB 3.0.
> However it relies on usb-conn-gpio driver to read the vbus and id
> gpio's and provide role switch. However the driver currently has
> only gpio-b-connector compatible present in ID table. Adding that
> in DT would mean that the device supports Type-B connector and not
> Type-c connector. Thanks to Dmitry Baryshkov for pointing it out [2].

USB-B connector is pretty simple, it really has just an ID pin and
VBUS input, which translates to two GPIOs being routed from the
_connector_ itself.

USB-C is much more complicated, it has two CC pins and a VBus power
pin. It is not enough just to measure CC pin levels. Moreover,
properly handling USB 3.0 inside a USB-C connector requires a separate
'orientation' signal to tell the host which two lanes must be used for
the USB SS signals. Thus it is no longer possible to route just two
pins from the connector to the SoC.

Having all that in mind, I suspect that you are not describing your
hardware properly. I suppose that you have a Type-C port controller /
redriver / switch, which handles CC lines communication and then
provides ID / VBUS signals to the host. In such a case, please
describe this TCPC in the DT file and use its compatible string
instead of "gpio-c-connector".

>
> This series intends to add that compatible in driver and bindings
> so that it can be used in QDU1000 IDP DT.
>
> [1]: https://lore.kernel.org/all/20240319091020.15137-3-quic_kbajaj@quicinc.com/
> [2]: https://lore.kernel.org/all/CAA8EJprXPvji8TgZu1idH7y4GtHtD4VmQABFBcRt-9BQaCberg@mail.gmail.com/
>
> Krishna Kurapati (2):
>   dt-bindings: connector: Add gpio-usb-c-connector compatible
>   usb: common: usb-conn-gpio: Update ID table to add usb-c connector
>
>  Documentation/devicetree/bindings/connector/usb-connector.yaml | 3 +++
>  drivers/usb/common/usb-conn-gpio.c                             | 1 +
>  2 files changed, 4 insertions(+)
>
> --
> 2.34.1
>


--
With best wishes
Dmitry