Message-ID: <99525a03-4a92-4bd0-b4b7-dfcd35a523c5@linaro.org>
Date: Wed, 10 Sep 2025 09:40:26 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Sebastian Reichel <sebastian.reichel@...labora.com>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I
 <kishon@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
 Frank Wang <frank.wang@...k-chips.com>,
 Zhang Yubing <yubing.zhang@...k-chips.com>, Andy Yan <andyshrk@....com>,
 Maud Spierings <maud_spierings@...mail.com>, linux-phy@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 1/2] dt-bindings: phy: rockchip-usbdp: add improved
 ports scheme

On 10/09/2025 01:52, Sebastian Reichel wrote:
> Hi,
> 
> On Sun, Sep 07, 2025 at 12:34:24AM +0300, Dmitry Baryshkov wrote:
>> On Sat, Sep 06, 2025 at 10:42:22PM +0200, Sebastian Reichel wrote:
>>> On Sat, Sep 06, 2025 at 10:24:54PM +0300, Dmitry Baryshkov wrote:
>>>> On Thu, Sep 04, 2025 at 08:26:02PM +0200, Sebastian Reichel wrote:
>>>>> Currently the Rockchip USBDP PHY as a very simply port scheme: It just
>>>>> offers a single port, which is supposed to point towards the connector.
>>>>> Usually with 2 endpoints, one for the USB-C superspeed port and one for
>>>>> the USB-C SBU port.
>>>>>
>>>>> This scheme is not good enough to properly handle DP AltMode, so add
>>>>> a new scheme, which has separate ports for everything. This has been
>>>>> modelled after the Qualcomm QMP USB4-USB3-DP PHY controller binding
>>>>> with a slight difference that there is an additional port for the
>>>>> USB-C SBU port as the Rockchip USB-DP PHY also contains the mux.
>>>>>
>>>>> Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
>>>>> ---
>>>>>   .../bindings/phy/phy-rockchip-usbdp.yaml           | 23 ++++++++++++++++++++++
>>>>>   1 file changed, 23 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/phy/phy-rockchip-usbdp.yaml b/Documentation/devicetree/bindings/phy/phy-rockchip-usbdp.yaml
>>>>> index 8b7059d5b1826fdec5170cf78d6e27f2bd6766bb..f728acf057e4046a4d254ee687af3451f17bcd01 100644
>>>>> --- a/Documentation/devicetree/bindings/phy/phy-rockchip-usbdp.yaml
>>>>> +++ b/Documentation/devicetree/bindings/phy/phy-rockchip-usbdp.yaml
>>>>> @@ -114,6 +114,29 @@ properties:
>>>>>         A port node to link the PHY to a TypeC controller for the purpose of
>>>>>         handling orientation switching.
>>>>>   
>>>>> +  ports:
>>>>> +    $ref: /schemas/graph.yaml#/properties/ports
>>>>> +    properties:
>>>>> +      port@0:
>>>>> +        $ref: /schemas/graph.yaml#/properties/port
>>>>> +        description:
>>>>> +          Output endpoint of the PHY for USB (or DP when configured into 4 lane
>>>>> +          mode), which should point to the superspeed port of a USB connector.
>>>>
>>>> What abourt USB+DP mode, where each one gets 2 lanes?
>>>
>>> Right, I guess we would need one port more and have one port for
>>> lane 0 + 1 and one port for 1 + 2. For USB-C both ports are
>>> connected to the USB-C superspeed port. For DP 4-lane mode the
>>> same is done for the input port of the connector. Last but not
>>> least for 2 lanes USB + 2 lanes DP, one port can be connected
>>> to the USB connector and one port can be connected to the DP
>>> connector.
>>
>> Hmm. I'm not sure what do you mean here. Basically, it should be:
>>
>> - Normal USB-C case with DP AltMode:
>>    + port@0 routed to connector's port@1 (through mux or retimer if any)
>>    + port@4 routed to connector's port@2 (through mux or retimer if any)
>>
>> - Actual DP or mini-DP connector:
>>    + port@0 routed to connector's sole port (most likely direcrly)
>>    + port@4 most likely unconnected (at least for now, dp-connector
>>      doesn't have AUX lines described)
>>
>> - Weird mode of having both USB-A or -C and actual DisplayPort
>>    + port@0 should get two endpoints, each having data-lines properties,
>>      one endpoint being connected to the USB port, another endpoint being
>>      connected to DP connector.
>>    + port@4 unconnected (yep, we should extend DP properties, maybe I'll
>>      send a patch)
> 
> That's a bit different from what I described, but sounds more
> sensible. Effectively the Rockchip USBDP PHY binding would need
> to deprecate rockchip,dp-lane-mux and switch to using data-lines
> on the endpoint instead, just like it is currently proposed for
> Qualcomm (I follow the T14S HDMI thread).
> 
> AFAIK the Rockchip PHY hardware does not support 1-lane DP, so the
> binding will have to forbid that. Shouldn't be a problem, though :)
> 
>> I'd say, the first two options are the most important ones. Unless you
>> have actual hardware that uses the USB + separate DP, I'd say, we can
>> ignore that part.
> 
> The RK3588 evaluation board routes the first two lanes to a USB-A
> connector and the second two lanes + AUX to a RTD2166 bridge, which
> converts it to VGA and then terminates on a VGA connector. I have
> that on my desk and can do some tests. But I don't have enough time
> for preparing patches right now - especially since the RTD2166 is
> not yet supported upstream.
> 
> Greetings,
> 
> -- Sebastian
> 
>>>>> +      port@1:
>>>>> +        $ref: /schemas/graph.yaml#/properties/port
>>>>> +        description: Incoming endpoint from the USB controller
>>>>> +
>>>>> +      port@2:
>>>>> +        $ref: /schemas/graph.yaml#/properties/port
>>>>> +        description: Incoming endpoint from the DisplayPort controller
>>>>> +
>>>>> +      port@3:
>>>>> +        $ref: /schemas/graph.yaml#/properties/port
>>>>> +        description:
>>>>> +          Output endpoint of the PHY for DP, which should either point to the
>>>>> +          SBU port of a USB-C connector or a DisplayPort connector input port.
>>>>
>>>> I would suggest describing this port as 'DisplayPort AUX signals to be
>>>> connected to the SBU port of a USB-C connector (maybe through the
>>>> additinal mux, switch or retimer)'. It should not be confused with the
>>>> actual DisplayPort signals (as those go through the port@0).

This is the use-case we're trying to support aswell on the Radxa Dragon Q6A.

Neil

>>>>
>>>> In the Qualcomm world we currently do not describe this link from the
>>>> PHY to the gpio-mux or retimer, but I think we will have to do that
>>>> soon.
>>>
>>> It does looks like no upstream platform does a proper description of
>>> USB-C setups :(
>>>
>>> Thanks for having a look,
>>>
>>> -- Sebastian
>>
>>
>>
>>> _______________________________________________
>>> Linux-rockchip mailing list
>>> Linux-rockchip@...ts.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-rockchip
>>
>>
>> -- 
>> With best wishes
>> Dmitry

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