Re: [PATCH v3 2/4] dt-bindings: media: add Maxim MAX96714F GMSL2 Deserializer

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Hi Sakari,

Thanks for the review!

On 2/9/24 10:48, Sakari Ailus wrote:
Hi Julien,

On Thu, Jan 11, 2024 at 02:03:47PM +0100, Julien Massot wrote:
Add DT bindings for Maxim MAX96714F GMSL2 Deserializer.

Signed-off-by: Julien Massot <julien.massot@xxxxxxxxxxxxx>

---
Change since v2:
  - remove reg description
  - rename enable gpio to powerdown
  - use generic node name: i2c, serializer, deserializer
---
  .../bindings/media/i2c/maxim,max96714f.yaml   | 171 ++++++++++++++++++
  1 file changed, 171 insertions(+)
  create mode 100644 Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml

diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml
new file mode 100644
index 000000000000..2423d166c954
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml
@@ -0,0 +1,171 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2024 Collabora Ltd.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/media/i2c/maxim,max96714f.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Maxim MAX96714 GMSL2 to CSI-2 Deserializer
+
+maintainers:
+  - Julien Massot <julien.massot@xxxxxxxxxxxxx>
+
+description: |
+  The MAX96714F deserializer converts GMSL2 serial inputs into MIPI
+  CSI-2 D-PHY or C-PHY formatted output. The device allows the GMSL2 link to

Description is wrong if the MAX96717F is supporting C-PHY MAX96714F doesn't.
I will remove the mention to C-PHY sorry for the confusion.

+  simultaneously transmit bidirectional control-channel data while forward
+  video transmissions are in progress. The MAX96714F can connect to one
+  remotely located serializer using industry-standard coax or STP
+  interconnects. The device cans operate in pixel or tunnel mode. In pixel mode
+  the MAX96714F can select individual video stream, while the tunnel mode forward all
+  the MIPI data received by the serializer.
+
+  The GMSL2 serial link operates at a fixed rate of 3Gbps in the
+  forward direction and 187.5Mbps in the reverse direction.
+
+properties:
+  compatible:
+    const: maxim,max96714f
+
+  reg:
+    maxItems: 1
+
+  powerdown-gpios:
+    maxItems: 1
+    description:
+      Specifier for the GPIO connected to the PWDNB pin.
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        unevaluatedProperties: false
+        description: GMSL Input
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+            description:
+              Endpoint for GMSL2-Link port.
+
+      port@1:
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
+        description: CSI-2 Output port
+
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+
+            properties:
+              data-lanes:
+                minItems: 1
+                maxItems: 4
+
+              link-frequencies:
+                maxItems: 1
+
+              bus-type:
+                enum:
+                  - 4 # MEDIA_BUS_TYPE_CSI2_DPHY

MEDIA_BUS_TYPE_CSI2_CPHY (1) is missing. Even if the driver doesn't support
it, it would be best to list it here.

After verification the hardware only support D-PHY and not C-PHY, will
drop the required
property for 'bus-type'.


+
+            required:
+              - data-lanes
+              - bus-type
+
+    required:
+      - port@1

Why port@1 but not port@0?

The device can be used as a pattern generator, so this is fine not to
have a serializer connected to the port@0, but it makes no sense to leave the deserializer CSI port not connected.


+
+  i2c-gate:
+    $ref: /schemas/i2c/i2c-controller.yaml
+    unevaluatedProperties: false
+    description: |
+      The MAX96714 will pass through and forward the I2C requests from the
+      incoming I2C bus over the GMSL2 link. Therefore it supports an i2c-gate
+      subnode to configure a serializer.
+
+  port0-poc-supply:
+    description: Regulator providing Power over Coax for the GMSL port
+
+required:
+  - compatible
+  - reg
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/media/video-interfaces.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        deserializer@28 {
+            compatible = "maxim,max96714f";
+            reg = <0x28>;
+            powerdown-gpios = <&main_gpio0 37 GPIO_ACTIVE_LOW>;
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                port@0 {
+                    reg = <0>;
+                    max96714_gmsl_in: endpoint {
+                        remote-endpoint = <&max96917f_gmsl_out>;
+                    };
+                };
+
+                port@1 {
+                    reg = <1>;
+                    max96714_csi_out: endpoint {
+                        bus-type = <MEDIA_BUS_TYPE_CSI2_DPHY>;
+                        clock-lanes = <0>;

clock-lanes isn't listed in bindings. You can drop it from here.
Ok


+                        data-lanes = <1 2 3 4>;
+                        link-frequencies = /bits/ 64 <400000000>;
+                        remote-endpoint = <&csi_in>;
+                    };
+                };
+            };
+
+            i2c-gate {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                serializer@40 {
+                    compatible = "maxim,max96717f";
+                    reg = <0x40>;
+                    gpio-controller;
+                    #gpio-cells = <2>;
+                    #clock-cells = <0>;
+
+                    ports {
+                        #address-cells = <1>;
+                        #size-cells = <0>;
+
+                        port@0 {
+                            reg = <0>;
+                            max96717f_csi_in: endpoint {
+                                data-lanes = <1 2>;
+                                lane-polarities = <1 0 1>;

Shouldn't lane-polarities be mentioned in bindings, too?

You are right I will add lane-polarities to my next patchset.

+                                remote-endpoint = <&sensor_out>;
+                            };
+                        };
+
+                        port@1 {
+                            reg = <1>;
+                            max96917f_gmsl_out: endpoint {
+                                remote-endpoint = <&max96714_gmsl_in>;
+                            };
+                        };
+                    };
+                };
+            };
+        };
+    };
+...


Best regards,

--
Julien Massot
Senior Software Engineer
Collabora Ltd.
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
Registered in England & Wales, no. 5513718




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