lkml.org 
[lkml]   [2020]   [Jan]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [Patch V2 01/18] dt-bindings: phy: tegra-xusb: Add usb-role-switch
    On Fri, Dec 20, 2019 at 04:08:30PM +0800, JC Kuo wrote:
    >
    > 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 changes
    > >> for OTG/Peripheral capable USB 2 ports.
    > >>
    > >> Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
    > >> ---
    > >> 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-xusb-padctl.txt b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
    > >> index 9fb682e..23bf354 100644
    > >> --- a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
    > >> +++ b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
    > >> @@ -174,6 +174,12 @@ Required properties:
    > >> - "device": for USB device mode
    > >> - "otg": for USB OTG mode
    > >>
    > >> +Required properties for OTG/Peripheral capable USB2 ports:
    > >> +- usb-role-switch: Boolean property to indicate that the port support OTG or
    > >
    > > "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:
    > >
    > > "... 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.
    >
    > 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 which
    > 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 = "otg", isn't it? In all other
    cases the functionality is fixed (either host or peripheral) and the
    mode cannot be switched.

    Thierry
    [unhandled content-type:application/pgp-signature]
    \
     
     \ /
      Last update: 2020-01-10 12:17    [W:4.805 / U:0.312 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site