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[46.91.239.63]) by smtp.gmail.com with ESMTPSA id s16sm1827624wrn.78.2020.01.10.03.16.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jan 2020 03:16:33 -0800 (PST) Date: Fri, 10 Jan 2020 12:16:33 +0100 From: Thierry Reding To: JC Kuo Cc: Nagarjuna Kristam , balbi@kernel.org, gregkh@linuxfoundation.org, jonathanh@nvidia.com, mark.rutland@arm.com, robh+dt@kernel.org, kishon@ti.com, devicetree@vger.kernel.org, linux-tegra@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [Patch V2 01/18] dt-bindings: phy: tegra-xusb: Add usb-role-switch Message-ID: <20200110111633.GA2233456@ulmo> References: <1576660591-10383-1-git-send-email-nkristam@nvidia.com> <1576660591-10383-2-git-send-email-nkristam@nvidia.com> <20191219130503.GG1440537@ulmo> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="uAKRQypu60I7Lcqm" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.13.1 (2019-12-14) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --uAKRQypu60I7Lcqm Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Dec 20, 2019 at 04:08:30PM +0800, JC Kuo wrote: >=20 > On 12/19/19 9:05 PM, Thierry Reding wrote: > > On Wed, Dec 18, 2019 at 02:46:14PM +0530, Nagarjuna Kristam wrote: > >> Add usb-role-switch property for Tegra210 and Tegra186 platforms. This > >> entry is used by XUSB pad controller driver to register for role chang= es > >> for OTG/Peripheral capable USB 2 ports. > >> > >> Signed-off-by: Nagarjuna Kristam > >> --- > >> V2: > >> - Moved usb-role-switch to seperate Required section as suggested by = Thierry. > >> - Added reference to usb/usb-conn-gpio.txt for connector subnode. > >> --- > >> .../devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt |= 6 ++++++ > >> 1 file changed, 6 insertions(+) > >> > >> diff --git a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xus= b-padctl.txt b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-p= adctl.txt > >> index 9fb682e..23bf354 100644 > >> --- a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padct= l.txt > >> +++ b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padct= l.txt > >> @@ -174,6 +174,12 @@ Required properties: > >> - "device": for USB device mode > >> - "otg": for USB OTG mode > >> =20 > >> +Required properties for OTG/Peripheral capable USB2 ports: > >> +- usb-role-switch: Boolean property to indicate that the port support= OTG or > >=20 > > "supports", and also, why if it supports OTG *or* peripheral? Doesn't > > OTG imply peripheral? OTG means it can be either peripheral or host, > > right? So I think the end of that sentence can be just: > >=20 > > "... the port supports OTG." > An USB OTG port is capable of both USB host and peripheral operations. An= USB > peripheral port can only act as an USB peripheral. >=20 > The micro USB ports found on Jetson TX1/TX2 platforms are micro-AB ports = which > should implement both host and peripheral capabilities. We say such ports > support OTG. The micro USB port found on Jetson Nano is a micro-B port wh= ich > should implement peripheral capability only. We say such ports support > peripheral, rather than OTG. I the port supports only peripheral mode, why do we need to have a usb-role-switch property? Shouldn't we in that case have a mode property with value "device"? usb-mode-switch is only needed if mode =3D "otg", isn't it? In all other cases the functionality is fixed (either host or peripheral) and the mode cannot be switched. 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