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Message-ID: <3kefqzjewmsyzfvyi33kvlgjd6jphjg3fsnixb3of7yb3xkgs2@hgi6xfkgd653>
Date: Wed, 30 Jul 2025 22:13:47 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Chaoyi Chen <kernel@...kyi.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>, Sandy Huang <hjc@...k-chips.com>,
        Andy Yan <andy.yan@...k-chips.com>,
        Yubing Zhang <yubing.zhang@...k-chips.com>,
        Frank Wang <frank.wang@...k-chips.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Amit Sunil Dhamne <amitsd@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Chaoyi Chen <chaoyi.chen@...k-chips.com>,
        Dragan Simic <dsimic@...jaro.org>, Johan Jonker <jbx6244@...il.com>,
        Diederik de Haas <didi.debian@...ow.org>,
        Peter Robinson <pbrobinson@...il.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3 0/5] Add Type-C DP support for RK3399 EVB IND board

On Tue, Jul 29, 2025 at 05:00:27PM +0800, Chaoyi Chen wrote:
> From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
> 
> This series focuses on adding Type-C DP support for USBDP PHY and DP
> driver. The USBDP PHY and DP will perceive the changes in cable status
> based on the USB PD and Type-C state machines provided by TCPM. Before
> this, the USBDP PHY and DP controller of RK3399 sensed cable state
> changes through extcon, and devices such as the RK3399 Gru-Chromebook
> rely on them. This series should not break them.
> 

[....]

> ====
> 2. DP HPD event notify
> 
> The RK3399 has two USB/DP combo PHY and one CDN-DP controller. And
> the CDN-DP can be switched to output to one of the PHYs.
> 
> USB/DP PHY0 ---+
>                | <----> CDN-DP controller
> USB/DP PHY1 ---+

Could you please clarify this, can you switch DP stream between two
USB-C outputs? What happens if user plugs in DP dongles in both USB-C
ports?

> 
> BTW, one of the important things to do is to implement extcon-like
> notifications. I found include/drm/bridge/aux-bridge.h , but if the
> aux-bridge is used, the bridge chain would look like this:
> 
> PHY0 aux-bridge ---+
>                    | ----> CDN-DP bridge
> PHY1 aux-bridge ---+
> 
> Oh, CDN-DP bridge has two previous aux-bridge!
> 
> Now, I try to use drm_connector_oob_hotplug_event() to notify HPD
> state between PHY and CDN-DP controller.

Does it actually work? The OOB HPD event will be repoted for the usb-c
connector's fwnode, but the DP controller isn't connected to that node
anyhow. If I'm not mistaken, the HPD signal will not reach DP driver in
this case.

> 
> Patch1 add new Type-C mode switch for RK3399 USBDP phy binding.
> Patch2 add typec_mux and typec_switch for RK3399 USBDP PHY.
> Patch3 drops CDN-DP's extcon dependency when Type-C is present.
> Patch4 add missing dp_out port for RK3399 CDN-DP.
> Patch5 add Type-C DP support for RK3399 EVB IND board.
> 

-- 
With best wishes
Dmitry

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