Messages in this thread |  | | Date | Mon, 27 Jun 2022 18:36:53 +0530 | Subject | Re: [PATCH v3 1/3] dt-bindings: usb: dwc3: Add support for multiport related properties | From | Harsh Agarwal <> |
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On 6/10/2022 10:52 PM, Rob Herring wrote: > On Fri, Jun 10, 2022 at 05:25:25PM +0530, Harsh Agarwal wrote: >> On 6/9/2022 9:08 PM, Rob Herring wrote: >>> On Wed, Jun 08, 2022 at 11:06:25PM +0530, Harsh Agarwal wrote: >>>> Added support for multiport, mport, num_usb2_phy and num_usb3_phy >>>> properties. These properties are used to support devices having >>>> a multiport controller. >>>> >>>> Signed-off-by: Harsh Agarwal <quic_harshq@quicinc.com> >>>> --- >>>> .../devicetree/bindings/usb/snps,dwc3.yaml | 53 ++++++++++++++++++++++ >>>> 1 file changed, 53 insertions(+) >>>> >>>> diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml >>>> index d41265b..9332fa2 100644 >>>> --- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml >>>> +++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml >>>> @@ -343,6 +343,32 @@ properties: >>>> This port is used with the 'usb-role-switch' property to connect the >>>> dwc3 to type C connector. >>>> + multiport: >>> Again, I don't think this is going to play well if you need to describe >>> USB devices in your DT. For example, a USB hub with additional DT >>> properties. >> Thanks for the review Rob. >> Can you please explain why would one want to describe a USB hub in device >> tree ? > Because someone soldered a hub on the board and then connected extra > things like resets, GPIOs, supplies which are all outside of standard > USB. It's quite common... > > There's some flavors of Beagle boards that have a USB ethernet on board. > Guess what, they skipped out on a eeprom and so the device and a MAC > address has to be described in DT (if you want a stable MAC addr). > >> IF USB hub is attached to a root port , it would be enumerated by the SW. I >> am not clear how DT is coming >> into picture. Even if there was a scenario to add DT properties for a hub, >> then this multiport node would be like a nop >> as it just helps us to get the PHY phandles in a proper way. > It won't be enumerated by the SW if it has to be powered on first using > non-standard resources. > >> Do you feel we still might have a problem with multiport node ? > A board design could have a hub or device on any or all your ports. > >>>> + description: >>>> + If a single USB controller supports multiple ports, then it's referred to as >>>> + a multiport controller. Each port of the multiport controller can support >>>> + either High Speed or Super Speed or both and have their own PHY phandles. Each >>>> + port is represented by "mport" node and all the "mport" nodes are grouped >>>> + together inside the "multiport" node where individual "mport" node defines the >>>> + PHYs supported by that port. >>>> + >>>> + num_usb2_phy: >>>> + description: Total number of HS-PHYs defined by the multiport controller. >>>> + $ref: /schemas/types.yaml#/definitions/uint32 >>>> + >>>> + num_usb3_phy: >>>> + description: Total number of SS-PHYs defined by the multiport controller. >>>> + $ref: /schemas/types.yaml#/definitions/uint32 >>>> + >>>> + mport: >>>> + description: Each mport node represents one port of the multiport controller. >>>> + oneOf: >>>> + - required: >>>> + - usb-phy >>> This is deprecated. Why are you adding it? >> Do you mean "usb-phy" is deprecated ? > It is replaced by 'phys'. Any new user should use 'phys'. > >> Internally we use usb-phy with our downstream GLUE driver > Upstream does not care about that. > >>>> + - required: >>>> + - phys >>>> + - phy-names >>> Other multi port USB hosts just have a list of phys. Why can't you just >>> use phy-names to identify each phy: >>> >>> phy-names = "port0-hs", "port0-ss", "port1-hs", "port1-ss", "port2-hs", >>> "port3-hs"; >> With the above method we would have to do some kind of string parsing on the >> phy-names to get the HS and SS PHYs as we need to cater to different >> combinations of Ports ( some support HS+SS , other supports SS only). > You are doing string parsing anyways to get the child nodes and > properties. > >> So one challenge here is with the "usb-phy". There we directly define the >> phy phandles and that might/might-not have proper sub-strings. eg >> USB_QMP_PHY . So extracting PHYS could be tricky if the phy-handle does not >> have proper substring like "SS" "HS" etc. > The schema can and should enforce that you have the proper strings. Hi Rob, Apologies for replying late.
I get your concern. Yes we can remove the "multiport" node and instead define the USB phy phandles all in one place. Still I would need to add support for both generic-phy and usb-phy framework as downstream many vendors are using "usb-phy" and it's supported by ACK as well. This would not regress anything with Generic PHY.
@Greg can you please comment as ACK has support for usb-phy framework.
Now coming to implementation, let's consider a 4 port USB multiport controller having 4 HS PHYs and 2 SS PHYs. We can have two approaches here
#1 -> If we could mandate using "HS" or "SS" as substring in phy-names or usb-phy, then we can calculate number of HS and SS phy and also get corresponding PHY nodes. Only concern here is that downstream vendors might need to change their existing usb-phy names and add proper substring if they are not doing so ;
phy = <&usb-hs-phy>,<&usb-ss-phy>, <&usb-hs-phy1>, <&usb-ss-phy1>, <&usb-hs-phy2>, <&usb-hs-phy3>;
phy-names = "port0-hs", "port0-ss", "port1-hs", "port1-ss", "port2-hs", "port3-hs";
OR
#2-> We could mandate defining the USB phy in HS - SS pairs. For ports that has only HS PHY, we would need to define usb_nop_phy in SS place. Then we can calculate the number of HS & SS phys and get corresponding PHY nodes by using simple fact that HS phy would be defined at odd places & SS phy defined at even. Here substrings are not mandated.
phy = <&usb-hs-phy>,<&usb-qmp-phy>, <&usb-hs-phy1>, <&usb-qmp-phy1>, <&usb-hs-phy2>, <&usb_nop_phy> <&usb-hs-phy3>, <&usb_nop_phy>;
phy-names = "port0-hs", "port0-ss", "port1-hs", "port1-ss", "port2-hs", "usb-nop", "port3-hs", "usb-nop";
Please let me know if you prefer any approach here or have any suggestions.
> > >> We cannot break existing implementation and so we thought of going with the >> "multiport" node approach, listing below some flexibility : > How would this break? > >> 1. Better representation of the PHYs and it's relation with a port. >> 2. Here for each port we pick the first PHY as HS and 2nd PHY as SS as we >> have been doing traditionally. >> So for "usb-phy" we need not care how the PHY handles are named. >> >> 3. It's future proof incase we need to add additional properties specific to >> a port. We can just add those properties inside MP_1 or MP_2 etc. >> Though nothing like this has yet been implemented. > Then you have to consider how the standard USB device binding fits into > this, and it needs to work for anyone with multiple ports. The > usb-hcd.yaml schema already defines that child nodes represent a USB > device attached to a port on the host. 'reg' is the port number. > > Rob
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