Re: [PATCH v2 1/4] dt-bindings: Add cros-ec Type C port driver

Resending (because I didn't send it in PlainText mode, so the MLs
blocked the email). Sorry.


On Tue, Feb 11, 2020 at 11:00 AM Prashant Malani [off-list ref] wrote:

Hi Enric,

Thanks as always for reviewing the patch. Kindly see my responses inline:

On Tue, Feb 11, 2020 at 2:28 AM Enric Balletbo i Serra [off-list ref] wrote:

quoted

Hi Prashant,

On 7/2/20 21:37, Prashant Malani wrote:

quoted

Some Chrome OS devices with Embedded Controllers (EC) can read and
modify Type C port state.

Add an entry in the DT Bindings documentation that lists out the logical
device and describes the relevant port information, to be used by the
corresponding driver.

Signed-off-by: Prashant Malani <redacted>
---

Changes in v2:
- No changes. Patch first introduced in v2 of series.

 .../bindings/chrome/google,cros-ec-typec.yaml | 77 +++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/chrome/google,cros-ec-typec.yaml

diff --git a/Documentation/devicetree/bindings/chrome/google,cros-ec-typec.yaml b/Documentation/devicetree/bindings/chrome/google,cros-ec-typec.yaml
new file mode 100644
index 00000000000000..46ebcbe76db3c2
--- /dev/null
+++ b/Documentation/devicetree/bindings/chrome/google,cros-ec-typec.yaml

@@ -0,0 +1,77 @@
+# SPDX-License-Identifier: GPL-2.0

I think that Google is fine with the dual licensing here. Would be good if this
can be (GPL-2.0-only OR BSD-2-Clause)

Thanks for catching this. I will update it in the next version.

quoted

quoted

+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/chrome/google,cros-ec-typec.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Google Chrome OS EC(Embedded Controller) Type C port driver.
+
+maintainers:
+  - Benson Leung [off-list ref]
+  - Prashant Malani [off-list ref]
+
+description:
+  Chrome OS devices have an Embedded Controller(EC) which has access to
+  Type C port state. This node is intended to allow the host to read and
+  control the Type C ports. The node for this device should be under a
+  cros-ec node like google,cros-ec-spi.
+
+properties:
+  compatible:
+    const: google,cros-ec-typec
+
+  port:
+    description: A node that represents a physical Type C port on the
+      device.
+    type: object
+    properties:
+      port-number:
+        description: The number used by the Chrome OS EC to identify
+          this type C port.
+        $ref: /schemas/types.yaml#/definitions/uint32

Any range of values allowed? 0 is okay?

0 is acceptable. Looks like Chrome OS EC numbers the ports as 0 to (num_ports - 1).
Actually, looking at it more closely, the port info EC command struct uses uint8_t (https://elixir.bootlin.com/linux/latest/source/include/linux/platform_data/cros_ec_commands.h#L4879)
Also, num_ports cannot be larger than: https://elixir.bootlin.com/linux/latest/ident/EC_USB_PD_MAX_PORTS

So perhaps this should be updated to say it can be any value from 0 - EC_USB_PD_MAX_PORTS ? (Not sure if I can reference #defines from header files in the DT bindings file....)

quoted

quoted

+      power-role:

Sorry if this question is silly, aren't this and below properties the same as
provided by usb-connector?  Can't this be usb-c-connector?

Documentation/devicetree/bindings/connector/usb-connector.txt

That's correct, it is the same. I think there is a slight difference between the properties of usb-connector (what properties are defined as optional and required) so I don't know if we can re-use usb-connector.
TBH I wasn't sure about this myself. I am also not sure whether there will be an issue with usb-c-connector being "claimed" by another driver. I think Heikki could perhaps guide us here.

quoted

quoted

+        description: Determines the power role that the Type C port will
+          adopt.
+        oneOf:
+          - items:
+            - const: sink
+            - const: source
+            - const: dual
+      data-role:
+        description: Determines the data role that the Type C port will
+          adopt.
+        oneOf:
+          - items:
+            - const: host
+            - const: device
+            - const: dual
+      try-power-role:
+        description: Determines the preferred power role of the Type C port.
+        oneOf:
+          - items:
+            - const: sink
+            - const: source
+            - const: dual
+
+    required:
+      - port-number
+      - power-role
+      - data-role
+      - try-power-role
+
+required:
+  - compatible
+  - port
+
+examples:
+  - |+

Rob can confirm, but I think is a good practice add the parent node, so add the
cros-ec-spi node here?

Done. Will add it in the next version.

quoted

quoted

+    typec {
+      compatible = "google,cros-ec-typec";
+
+      port@0 {

You can run:

  make dt_binding_check DT_SCHEMA_FILES=<...>/chrome/google,cros-ec-typec.yaml

And you'll get an error:

 typec: 'port' is a required property

Noted. I will run this check before pushing next time and fix the error.

quoted

quoted

+        port-number = <0>;
+        power-role = "dual";
+        data-role = "dual";
+        try-power-role = "source";
+      };
+    };

Thanks,

 Enric

Thanks,

-Prashant