Re: (EXT) [RFC PATCH v4 03/12] dt-bindings: media: Add bindings for bcm2835-unicam

Hi Alexander,

On Fri, Feb 04, 2022 at 09:50:06AM +0100, Alexander Stein wrote:

Am Donnerstag, 3. Februar 2022, 18:50:00 CET schrieb Jean-Michel Hautbois:

quoted

Introduce the dt-bindings documentation for bcm2835 CCP2/CSI2 Unicam
camera interface. Also add a MAINTAINERS entry for it.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Naushir Patuck <redacted>
Signed-off-by: Jean-Michel Hautbois <redacted>

---
v4:
- make MAINTAINERS its own patch
- describe the reg and clocks correctly
- use a vendor entry for the number of data lanes
---
 .../bindings/media/brcm,bcm2835-unicam.yaml   | 110 ++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644
Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml

diff --git
a/Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml
b/Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml new file
mode 100644
index 000000000000..0725a0267c60

--- /dev/null
+++ b/Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml

@@ -0,0 +1,110 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/media/brcm,bcm2835-unicam.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom BCM283x Camera Interface (Unicam)
+
+maintainers:
+  - Raspberry Pi Kernel Maintenance <kernel-list@raspberrypi.com>
+
+description: |-
+  The Unicam block on BCM283x SoCs is the receiver for either
+  CSI-2 or CCP2 data from image sensors or similar devices.
+
+  The main platform using this SoC is the Raspberry Pi family of boards.
+  On the Pi the VideoCore firmware can also control this hardware block,
+  and driving it from two different processors will cause issues.
+  To avoid this, the firmware checks the device tree configuration
+  during boot. If it finds device tree nodes starting by csi then
+  it will stop the firmware accessing the block, and it can then
+  safely be used via the device tree binding.
+
+properties:
+  compatible:
+    const: brcm,bcm2835-unicam
+
+  reg:
+    items:
+      - description: Unicam block.
+      - description: Clock Manager Image (CMI) block.
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: Clock to drive the LP state machine of Unicam.
+      - description: Clock for the vpu (core clock).
+
+  clock-names:
+    items:
+      - const: lp
+      - const: vpu
+
+  power-domains:
+    items:
+      - description: Unicam power domain
+
+  brcm,num-data-lanes:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [ 2, 4 ]
+    description: Number of data lanes on the csi bus

There is already data-lanes in Documentation/devicetree/bindings/media/video-
interfaces.yaml. AFAICS these two are identical. Can't the video-
interface.yaml be used for this? I'm no expert TBH.

This is the number of data lanes that the Unicam instance supports.
There are two Unicam instances, and they can have 2 or 4 data lanes
depending on the SoC. The data-lanes endpoint property indicates the
number of lanes used on a particular board.

-- 
Regards,

Laurent Pinchart