Re: [PATCH v4 2/2] media: dt-bindings: media: i2c: Add IMX300 CMOS sensor binding

On Sun, Jan 17, 2021 at 06:51:04PM +0100, AngeloGioacchino Del Regno wrote:

Il 17/01/21 00:44, Sakari Ailus ha scritto:

quoted

Hi AngeloGioacchino,

On Wed, Jan 13, 2021 at 07:29:34PM +0100, AngeloGioacchino Del Regno wrote:

quoted

Add YAML device tree binding for IMX300 CMOS image sensor, and
the relevant MAINTAINERS entries.

Signed-off-by: AngeloGioacchino Del Regno <redacted>
---
  .../bindings/media/i2c/sony,imx300.yaml       | 112 ++++++++++++++++++
  MAINTAINERS                                   |   7 ++
  2 files changed, 119 insertions(+)
  create mode 100644 Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml

diff --git a/Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml b/Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml
new file mode 100644
index 000000000000..4fa767feea80
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml

@@ -0,0 +1,112 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/media/i2c/sony,imx300.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Sony 1/2.3-Inch 25Mpixel Stacked CMOS Digital Image Sensor
+
+maintainers:
+  - AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
+
+description: |-
+  The Sony IMX300 is a 1/2.3-inch Stacked CMOS (Exmor-RS) digital image
+  sensor with a pixel size of 1.08um and an active array size of
+  5948H x 4140V. It is programmable through I2C interface at address 0x10.
+  Image data is sent through MIPI CSI-2, which is configured as either 2 or
+  4 data lanes.
+
+properties:
+  compatible:
+    const: sony,imx300
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1

Please add assigned clock related properties; see
Documentation/driver-api/media/camera-sensor.rst .

Will do!

quoted

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+
+  vdig-supply:
+    description:
+      Digital I/O voltage supply, 1.15-1.20 volts
+
+  vana-supply:
+    description:
+      Analog voltage supply, 2.2 volts
+
+  vddl-supply:
+    description:
+      Digital core voltage supply, 1.8 volts
+
+  reset-gpios:
+    description: |-
+      Reference to the GPIO connected to the xclr pin, if any.
+      Must be released (set high) after all supplies are applied.
+
+  # See ../video-interfaces.txt for more details
+  port:
+    type: object
+    properties:
+      endpoint:
+        type: object
+
+        properties:
+          data-lanes:
+            description: |-
+              The driver only supports four-lane operation.

This can be removed as bindings describe hardware, not driver operation.

Ack.

quoted

quoted

+            items:
+              - const: 0
+              - const: 1
+              - const: 2
+              - const: 3

Two lanes here, too?

The driver only supports four-lane operation.
I am 100% sure that this sensor can also work with two lanes, but it needs
special configuration which I'm not able to produce, nor test.

As you may imagine (and as you can read in the driver itself), all of this
was reverse-engineering work, as Sony has never released any datasheet for
this sensor - and I have a hunch - they never will (but that's another
story).

That's all fine. The bindings describe the hardware, not the driver's
capabilities.

quoted

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+
+          clock-noncontinuous: true
+
+          link-frequencies:
+            $ref: /schemas/types.yaml#/definitions/uint64-array
+            description:
+              Allowed data bus frequencies. The driver currently needs
+              to switch between 780000000 and 480000000 Hz in order to
+              guarantee functionality of all modes.

You can omit this description, too.

The intention here was to be clear and provide as much information as I
could gather during the very time-consuming reverse engineering process that
took place in the making of this driver.

But okay, I will remove this.

Again, this is about the hardware, not the driver. That information is also
part of the driver.

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+
+        required:
+          - data-lanes
+          - link-frequencies
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - vana-supply
+  - vdig-supply
+  - vddl-supply

Are the regulators really required? I'm not quite sure about the
established practices; still the common case is that one or two of these
are hard-wired.

On all the Sony phones that I have (....many), with MSM8956, MSM8996,
SDM630, equipped with the IMX300 camera assy, none of these three are
hard-wired: sometimes they're wired to the LDOs of the PMIC, sometimes
they're wired to fixed LDOs, enabled through GPIOs (fixed-regulator binding
in this case).

So.. yeah, they're really required.

As noted, that depends on the board. You just happen to have some where
they are not hard-wired.

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+  - port
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c0 {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        imx300: sensor@10 {
+            compatible = "sony,imx300";
+            reg = <0x10>;
+            clocks = <&imx300_xclk>;
+            vana-supply = <&imx300_vana>;   /* 2.2v */
+            vdig-supply = <&imx300_vdig>;   /* 1.2v */
+            vddl-supply = <&imx300_vddl>;   /* 1.8v */
+
+            port {
+                imx300_0: endpoint {
+                    remote-endpoint = <&csi1_ep>;
+                    data-lanes = <0 1 2 3>;
+                    clock-noncontinuous;
+                    link-frequencies = /bits/ 64 <780000000 480000000>;
+                };
+            };
+        };
+    };
+
+...

diff --git a/MAINTAINERS b/MAINTAINERS
index ad9abb42f852..5e0f08f48d48 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -16633,6 +16633,13 @@ T:	git git://linuxtv.org/media_tree.git
  F:	Documentation/devicetree/bindings/media/i2c/imx290.txt
  F:	drivers/media/i2c/imx290.c
+SONY IMX300 SENSOR DRIVER
+M:	AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
+L:	linux-media@vger.kernel.org

Please also add the git tree.

Ideally also the MAINTAINERS change comes with the first patch adding the
files, which should be the DT bindings. I.e. just reverse the order of the
patches.

I haven't added it because last time I did that I got reviews saying that if
I'm not the owner of the git tree I shall not put it in.
Though, if that's a requirement for media, then I didn't know that...

The documentation in MAINTAINERS doesn't say that at least.

I think it'd be useful to have it.

quoted

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+S:	Maintained
+F:	Documentation/devicetree/bindings/media/i2c/sony,imx300.yaml
+F:	drivers/media/i2c/imx300.c
+
  SONY IMX319 SENSOR DRIVER
  M:	Bingbu Cao [off-list ref]
  L:	linux-media@vger.kernel.org

Thank you for your review!

You're welcome!

-- 
Sakari Ailus