Re: [RFC v4 1/5] dt-bindings: usb: Add bindings to support multiport properties

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On 1/16/2023 10:04 PM, Rob Herring wrote:
On Sun, Jan 15, 2023 at 05:11:42PM +0530, Krishna Kurapati wrote:
Add bindings to indicate properties required to support multiport
on Snps Dwc3 controller.

Signed-off-by: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx>
---
  .../devicetree/bindings/usb/snps,dwc3.yaml    | 53 ++++++++++++++++---
  1 file changed, 47 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
index 6d78048c4613..3ea051beb2f8 100644
--- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
+++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
@@ -81,15 +81,26 @@ properties:
phys:
      minItems: 1
-    maxItems: 2
+    maxItems: 8
phy-names:
      minItems: 1
-    maxItems: 2
-    items:
-      enum:
-        - usb2-phy
-        - usb3-phy
+    maxItems: 8
+    oneOf:
+    - items:
+        enum:
+          - usb2-phy
+          - usb3-phy
+    - items:
+        enum:
+          - usb2-phy_port0
+          - usb2-phy_port1
+          - usb2-phy_port2
+          - usb2-phy_port3
+          - usb3-phy_port0
+          - usb3-phy_port1
+          - usb3-phy_port2
+          - usb3-phy_port3

usbN-portM

resets:
      minItems: 1
@@ -360,6 +371,22 @@ properties:
      description:
        Enable USB remote wakeup.
+ num-ports:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      This property indicates the number of ports present on the target that
+      are to be serviced by the DWC3 controller.
+    minimum: 1
+    maximum: 4
+
+  num-ss-ports:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      This property indicates the number of SS capable ports present on the
+      target that are to be serviced by the DWC3 controller.
+    minimum: 1
+    maximum: 4

This information is redundant. 'phy-names' tells you how many ports of
each.

Hi Rob,

Thanks for the review. The reason I wanted to introduce two more variables is to get info on number of ports and ss-capable ports present on hardware whether or not the user provides them in DTSI file.

In the code there are two types of per port / per phy operations:
a) Modifying GUSB2PFYCFG and GUSB3PIPECTL registers per phy.
b) Generic Phy operations - per phy.

In today's code, if someone doesn't mention the SSPHY in DTSI, dwc->usb3_generic_phy will be NULL and any call to phy operations will just bail out. And irrespective of whether we provide SS Phy in DTSI or not, we still configure GUSB3PIPECTL register.

Consider the following cases:

1. There are 3 ports and 2 of them are SS capable and all phy's are mentioned in DTSI.

phy-names= "usb2-port0", "usb3-port0", "usb2-port1", "usb3-port1", "usb2-port2"

When we count them in the driver, we get num ports as 3 (presuming num-ports = num of hs ports) and num-ss-ports = 2.

Since there is no ambiguity in which all ports to configure, we can modify GUSB2PHYCFG registers for all 3 HS Phy's and GUSB3PIPECTL for both SS Phy's.
This is a proper scenario.

2. If the user skips providing SS Phy on Port-0, then:

phy-names= "usb2-port0", "usb2-port1", "usb3-port1", "usb2-port2"

If we count the phys, we end up getting num-ports=3 and num-ss-ports=1.

Since in the driver code, we are not keeping track of which ports are SS capable and which ones are not, we end up configuring GUSB2PIPECTL(port-0) instead of port-1 as the num-ss-ports is "1" which is incorrect.

3. If the user skips providing one complete port, in this case port-1 is skipped, then:

phy-names= "usb2-port0", "usb3-port0", "usb2-port2"

If we count the phys, we end up getting num-ports=2 and num-ss-ports=1.

Since in the driver code, we are not keeping track of which ports are SS capable and which ones are not, we end up configuring GUSB2PHYCFG(port-0) and GUSB2PHYCFG(port-1) instead of port-2 which is incorrect.

To avoid these scenarios, if we can get the exact number of SS Ports and Ports in total present on the HW, we can configure all the registers whether the phy's are provided in DTSI or not. (This is of no harm I believe as it still works in today's code)

Incase the 2nd and 3rd scenarios are not allowed and user *MUST* declare all the phy's in the DTSI, then I can go ahead and remove these properties and count them in the driver code.

Thanks,
Krishna,

+
  unevaluatedProperties: false
required:
@@ -388,4 +415,18 @@ examples:
        snps,dis_u2_susphy_quirk;
        snps,dis_enblslpm_quirk;
      };
+  - |
+    usb@4a000000 {
+      compatible = "snps,dwc3";
+      reg = <0x4a000000 0xcfff>;
+      interrupts = <0 92 4>;
+      clocks = <&clk 1>, <&clk 2>, <&clk 3>;
+      clock-names = "bus_early", "ref", "suspend";
+      num-ports = <2>;
+      num-ss-ports = <1>;
+      phys = <&usb2_phy0>, <&usb3_phy0>, <&usb2_phy1>;
+      phy-names = "usb2-phy_port0", "usb3-phy_port0", "usb2-phy_port1";
+      snps,dis_u2_susphy_quirk;
+      snps,dis_enblslpm_quirk;
+    };

Does a different number of phys really need its own example?

Rob



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