linux-kernel - Re: [RFC v4 2/5] usb: dwc3: core: Refactor PHY logic to support Multiport Controller

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Date:   Wed, 25 Jan 2023 12:49:11 -0800
From:   Jack Pham <quic_jackp@...cinc.com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC:     Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "Andy Gross" <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        "Konrad Dybcio" <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Felipe Balbi <balbi@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Pavan Kondeti <quic_pkondeti@...cinc.com>,
        Pratham Pratap <quic_ppratap@...cinc.com>,
        "Harsh Agarwal" <quic_harshq@...cinc.com>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        "quic_shazhuss@...cinc.com" <quic_shazhuss@...cinc.com>
Subject: Re: [RFC v4 2/5] usb: dwc3: core: Refactor PHY logic to support
 Multiport Controller

On Wed, Jan 25, 2023 at 07:08:10PM +0000, Thinh Nguyen wrote:

<snip>

> > +       /*
> > +        * If the controller is not host-only, then it must be a
> > +        * single port controller.
> > +        */

Thinh, is this a correct assumption?  Is it possible for the IP to be
synthesized to support both dual-role and multiple ports?  We know that
when operating in device mode only the first port can be used but the
additional ports would be usable when in host.

Thanks,
Jack

> > +       temp = readl(regs + DWC3_GHWPARAMS0);
> > +       hw_mode = DWC3_GHWPARAMS0_MODE(temp);
> > +       if (hw_mode != DWC3_GHWPARAMS0_MODE_HOST) {
> > +               dwc->num_ports = 1;
> > +               dwc->num_ss_ports = 1;
> > +               return 0;
> > +       }
> 
> This check should be done before we get into this function.