linux-kernel - Re: [PATCH v14 0/9] Add multiport support for DWC3 controllers

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Date: Tue, 6 Feb 2024 14:15:39 +0530
From: Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring
	<robh+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Wesley Cheng
	<quic_wcheng@...cinc.com>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        "Greg
 Kroah-Hartman" <gregkh@...uxfoundation.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Felipe Balbi
	<balbi@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_ppratap@...cinc.com>,
        <quic_jackp@...cinc.com>
Subject: Re: [PATCH v14 0/9] Add multiport support for DWC3 controllers



On 2/6/2024 2:13 PM, Dmitry Baryshkov wrote:
> On Tue, 6 Feb 2024 at 10:15, Krishna Kurapati PSSNV
> <quic_kriskura@...cinc.com> wrote:
>>
>>
>>
>> On 2/6/2024 1:30 PM, Dmitry Baryshkov wrote:
>>> Hi Krishna,
>>>
>>> On Tue, 6 Feb 2024 at 07:18, Krishna Kurapati <quic_kriskura@...cinc.com> wrote:
>>>>
>>>> Currently the DWC3 driver supports only single port controller which
>>>> requires at most two PHYs ie HS and SS PHYs. There are SoCs that has
>>>> DWC3 controller with multiple ports that can operate in host mode.
>>>> Some of the port supports both SS+HS and other port supports only HS
>>>> mode.
>>>>
>>>> This change primarily refactors the Phy logic in core driver to allow
>>>> multiport support with Generic Phy's.
>>>>
>>>> Changes have been tested on  QCOM SoC SA8295P which has 4 ports (2
>>>> are HS+SS capable and 2 are HS only capable).
>>>
>>> Thank you for your patches! Have you tested how this patchset
>>> interacts with the USB role-switching?
>>>
>>> I'm asking because it might be easier to define DT nodes for each of
>>> USB ports, which can carry the PHY properties (and also other DT
>>> properties if that's required, e.g. the ports / endpoints and
>>> usb-role-switch) rather than pushing all USB PHY links to the root DT
>>> node.
>>>
>>
>> Hi Dmitry,
>>
>>    Role switching doesn't work for Multiport controller as it is host
>> only capable. I don't think it will cause any issues for OTG capable
>> controllers because they only have one HS and SS phy present. So there
>> is no possibility or requirement for having endpoints per port in this case.
> 
> Is it going to remain host-only in future?
> 
> 
Yes. I believe these are designed that way. I don't know of any 
controllers that have multiple ports and device mode works. Device mode 
can work only on one port AFAIK.

Regards,
Krishna,