Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20190311095613.11371-1-narmstrong@baylibre.com>
 <20190311095613.11371-12-narmstrong@baylibre.com> <CAFBinCDU_6JEJJS8yZkq0rjbqKcy2eBKFaYqgX3txGMiO5U9Fg@mail.gmail.com>
 <5C8D0C2B.2010605@baylibre.com>
In-Reply-To: <5C8D0C2B.2010605@baylibre.com>
From:   Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date:   Sat, 16 Mar 2019 23:07:01 +0100
Message-ID: <CAFBinCDyTPLr+fNptpHa664pMqvp4X3Tv6166h_C+b0gHBJ-ZA@mail.gmail.com>
Subject: Re: [PATCH 11/11] arm64: dts: meson-g12a-x96-max: Enable USB
To:     Neil Armstrong <narmstrong@baylibre.com>
Cc:     khilman@baylibre.com, linux-amlogic@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Neil,

On Sat, Mar 16, 2019 at 3:46 PM Neil Armstrong <narmstrong@baylibre.com> wr=
ote:
>
>
>
> Le 15/03/2019 22:50, Martin Blumenstingl a =C3=A9crit :
> > Hi Neil,
> >
> > On Mon, Mar 11, 2019 at 10:58 AM Neil Armstrong <narmstrong@baylibre.co=
m> wrote:
> > [...]
> >> +&dwc2 {
> >> +       status =3D "okay";
> >> +};
> > your patch description states that this enables the "USB host ports"
> > but dwc2 is only used for peripheral mode (meaning: dr_mode =3D
> > "peripheral" or dr_mode =3D "otg").
> > do we still need to enable dwc2 in a host-only configuration?
>
> DWC2 is peripheral-only, but we can still manually switch one of the
> ports and use it as peripheral with a Type-A to Type-A cable, thus
> enabling dwc2.
thank you for the explanation!

> If the OTG capable PHYs was behind an USB Hub or directly connected to
> a device, we could disable dwc2, but for now this port is always tied
> to a physical Type-A or micro-USB connector.
>
> Maybe it would be sane to always enable dwc2, and disable it for specific
> boards only.
In case the port is connected to an USB hub we can add a comment to
the .dts to explain why dwc2 is being disabled. that way we don't need
a comment in each board.dts that it's enabled to support forced mode
switching.
in other words: I like this idea!


Regards
Martin