[PATCH v7 usb-next 4/4] dt-bindings: usb: xhci: include the roothub and a device in the example

[Martin Blumenstingl]

Hi Alan,

On Fri, Oct 27, 2017 at 9:55 PM, Alan Stern <stern at rowland.harvard.edu> wrote:
> On Fri, 27 Oct 2017, Martin Blumenstingl wrote:
>
>> Hi Rob,
>>
>> On Fri, Oct 27, 2017 at 5:29 AM, Rob Herring <robh at kernel.org> wrote:
>> > On Mon, Oct 23, 2017 at 11:57:18PM +0200, Martin Blumenstingl wrote:
>> >> This extends the existing example from the USB xHCI binding
>> >> documentation so it includes the roothub and an actual device.
>> >> The goal of this is to show that the roothub is specified alongside the
>> >> actual devices on the USB bus (which is important because a device on
>> >> the USB bus - for example a hub - might need it's own phys / phy-names
>> >> properties. modelling the roothub as separate device and not nesting the
>> >> other devices on the bus below the roothub allows us to keep the
>> >> properties, for example the PHYs, separated).
>> >>
>> >> Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
>> >> ---
>> >>  Documentation/devicetree/bindings/usb/usb-xhci.txt | 23 ++++++++++++++++++++++
>> >>  1 file changed, 23 insertions(+)
>> >>
>> >> diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
>> >> index 5b49ba9f2f9a..20e5ce2b016a 100644
>> >> --- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
>> >> +++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
>> >> @@ -42,4 +42,27 @@ Example:
>> >>               compatible = "generic-xhci";
>> >>               reg = <0xf0931000 0x8c8>;
>> >>               interrupts = <0x0 0x4e 0x0>;
>> >> +
>> >> +             #address-cells = <1>;
>> >> +             #size-cells = <0>;
>> >> +
>> >> +             /* see usb-roothub.txt */
>> >> +             roothub at 0 {
>> >> +                     compatible = "usb1d6b,3", "usb1d6b,2";
>> >> +                     #address-cells = <1>;
>> >> +                     #size-cells = <0>;
>> >> +                     reg = <0>;
>> >> +
>> >> +                     port at 1 {
>> >> +                             reg = <1>;
>> >> +                             phys = <&usb2_phy1>, <&usb3_phy1>;
>> >> +                             phy-names = "usb2-phy", "usb3-phy";
>> >> +                     };
>> >> +             };
>> >> +
>> >> +             /* see usb-device.txt */
>> >> +             hub: genesys at 1 {
>> >
>> > What do the 0 and 1 addresses correspond to?
>> 0 is the address of the root-hub, 1 is the first device on the root-hub
>> based on my previous dt-binding patch Arnd assumed that the devices
>> would be moved in the hierarchy: [0]
>> however, my understanding is that (at least for now) the root-hub node
>> (identified by reg = <0>) is used to describe only the root-hub (which
>> allows initializing the PHYs), not the devices that are connected to
>> it
>>
>> here's an example from my Khadas VIM (which matches the example from
>> my patch, except: a) it has a different USB hub connected at port 1 b)
>> it has two ports on the root-hub)
>> this is a stripped and commented version of "cat /sys/kernel/debug/usb/devices"
>>
>> T:  Bus=02 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=5000 MxCh= 0
>> D:  Ver= 3.00 Cls=09(hub  ) Sub=00 Prot=03 MxPS= 9 #Cfgs=  1
>> P:  Vendor=1d6b ProdID=0003 Rev= 3.14
>> -> (USB3 root-hub from a dwc3 controller) in the device-tree example
>> this belongs to &usb/roothub at 0
>>
>> T:  Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480  MxCh= 2
>> D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=01 MxPS=64 #Cfgs=  1
>> P:  Vendor=1d6b ProdID=0002 Rev= 3.14
>> -> (USB2 root-hub from a dwc3 controller) in the device-tree example
>> this also belongs to &usb/roothub at 0
>>
>> T:  Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=480  MxCh= 4
>> D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=01 MxPS=64 #Cfgs=  1
>> P:  Vendor=1a40 ProdID=0801 Rev= 1.00
>> -> (USB2 hub soldered to the board, connected to root-hub port 1) in
>> the device-tree example this belongs to &usb/genesys at 1
>>
>> T:  Bus=01 Lev=02 Prnt=02 Port=02 Cnt=01 Dev#=  3 Spd=480  MxCh= 0
>> D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
>> P:  Vendor=090c ProdID=1000 Rev= 7.22
>> -> USB thumb drive connected to the USB hub, not listed in the
>> device-tree example but it would be listed below &usb/genesys at 1
>
> Two things to be aware of:
>
>     1.  /sys/kernel/debug/usb/devices has an off-by-one error in the
>         "Port=" field.  Every value you see should actually be one
>         higher than it is.  It has been this way for many, many years
>         so we can't fix it now.
here's the output of "lsusb -t" (which is easier to read I guess):
# lsusb -t
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/0p, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/2p, 480M
   |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/4p, 480M
       |__ Port 3: Dev 3, If 0, Class=Mass Storage, Driver=usb-storage, 480M

>     2.  Port numbers are meaningless for root hubs, because root hubs
>         by definition are not connected to any upstream USB ports.
thanks for explaining


Regards,
Martin