linux-kernel - Re: [PATCH v3 14/17] dt-bindings: usb: Add ports to google,cros-ec-typec for DP altmode

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Message-ID: <172420048648.2348348.16719987576551800332.robh@kernel.org>
Date: Tue, 20 Aug 2024 19:34:47 -0500
From: "Rob Herring (Arm)" <robh@...nel.org>
To: Stephen Boyd <swboyd@...omium.org>
Cc: Daniel Scally <djrscally@...il.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Jonas Karlman <jonas@...boo.se>, Robert Foss <rfoss@...nel.org>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Rob Herring <robh+dt@...nel.org>, David Airlie <airlied@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Douglas Anderson <dianders@...omium.org>,
	Vinod Koul <vkoul@...nel.org>, Benson Leung <bleung@...omium.org>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	patches@...ts.linux.dev,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Prashant Malani <pmalani@...omium.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Pin-yen Lin <treapking@...omium.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-kernel@...r.kernel.org,
	Ivan Orlov <ivan.orlov0322@...il.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>, dri-devel@...ts.freedesktop.org,
	linux-usb@...r.kernel.org, linux-acpi@...r.kernel.org,
	chrome-platform@...ts.linux.dev,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Maxime Ripard <mripard@...nel.org>, Lee Jones <lee@...nel.org>,
	devicetree@...r.kernel.org, Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH v3 14/17] dt-bindings: usb: Add ports to
 google,cros-ec-typec for DP altmode


On Mon, 19 Aug 2024 15:38:28 -0700, Stephen Boyd wrote:
> Add a DT graph binding to google,cros-ec-typec so that it can combine
> DisplayPort (DP) and USB SuperSpeed (SS) data into a USB type-c endpoint
> that is connected to the usb-c-connector node's SS endpoint. This also
> allows us to connect the DP and USB nodes in the graph to the USB type-c
> connectors, providing the full picture of the USB type-c data flows in
> the system.
> 
> Allow there to be multiple typec nodes underneath the EC node so that
> one DT graph exists per DP bridge. The EC is actually controlling TCPCs
> and redrivers that combine the DP and USB signals together so this more
> accurately reflects the hardware design without introducing yet another
> DT node underneath the EC for USB type-c.
> 
> If the type-c ports are being shared between a single DP controller then
> the ports need to know about each other and determine a policy to drive
> DP to one type-c port. If the type-c ports each have their own dedicated
> DP controller then they're able to operate independently and enter/exit
> DP altmode independently as well. We can't connect the DP controller's
> endpoint to one usb-c-connector port@1 endpoint and the USB controller's
> endpoint to another usb-c-connector port@1 endpoint either because the
> DP muxing case would have DP connected to two usb-c-connector endpoints
> which the graph binding doesn't support.
> 
> Therefore, one typec node is required per the capabilities of the type-c
> port(s) being managed. This also lets us indicate which type-c ports the
> DP controller is wired to. For example, if DP was connected to ports 0
> and 2, while port 1 was connected to another DP controller we wouldn't
> be able to implement that without having some other DT property to
> indicate which output ports are connected to the DP endpoint.
> 
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
> Cc: Conor Dooley <conor+dt@...nel.org>
> Cc: Lee Jones <lee@...nel.org>
> Cc: Benson Leung <bleung@...omium.org>
> Cc: Guenter Roeck <groeck@...omium.org>
> Cc: Prashant Malani <pmalani@...omium.org>
> Cc: Tzung-Bi Shih <tzungbi@...nel.org>
> Cc: <devicetree@...r.kernel.org>
> Cc: <chrome-platform@...ts.linux.dev>
> Cc: Pin-yen Lin <treapking@...omium.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  .../bindings/mfd/google,cros-ec.yaml          |   7 +-
>  .../bindings/usb/google,cros-ec-typec.yaml    | 229 ++++++++++++++++++
>  2 files changed, 233 insertions(+), 3 deletions(-)
> 

Reviewed-by: Rob Herring (Arm) <robh@...nel.org>