Re: [RFC PATCH v2 3/7] media: dt-bindings: media: Add bindings for bcm2835-unicam

[Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>]

Hi Laurent,

On 22/01/2022 00:27, Laurent Pinchart wrote:
> Hi Jean-Michel,
> 
> Thank you for the patch.
> 
> On Fri, Jan 21, 2022 at 09:18:06AM +0100, Jean-Michel Hautbois wrote:
>> Introduce the dt-bindinds documentation for bcm2835 CCP2/CSI2 camera
> 
> s/bindinds/bindings/
> 
> I'd mention "Unicam" somewhere here.
> 
>> interface. Also add a MAINTAINERS entry for it.

Oh my, I tis not the right dts bindings patch, I mixed up my trees... :-/

Sorry for this I will send a v2.1 soon...

>>
>> Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
>> Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
>> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
>> ---
>> Dave: I assumed you were the maintainer for this file, as I based it on the
>> bcm2835-unicam.txt file. Are  you happy to be added directly as the
>> maintainer, or should this be specified as "Raspberry Pi Kernel
>> Maintenance <kernel-list@raspberrypi.com>"
>> - in v2: multiple corrections to pass the bot checking as Rob kindly
>>    told me.
>> ---
>>   .../bindings/media/brcm,bcm2835-unicam.yaml   | 103 ++++++++++++++++++
>>   MAINTAINERS                                   |   6 +
>>   2 files changed, 109 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..1427514142cf
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml
>> @@ -0,0 +1,103 @@
>> +# 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:
>> +  - Dave Stevenson <dave.stevenson@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 called csi0 or csi1 then
>> +  it will stop the firmware accessing the block, and it can then
>> +  safely be used via the device tree binding.
> 
> As mentioned in the review of the DT integration, the nodes should
> ideally be called just "csi", not "csi0" and "csi1" (maybe Rob could
> confirm this ?). Dave, is there a way the firmware could be updated to
> also hand over control of the Unicam instances to Linux when a "csi"
> node is found, not just "csi0" or "csi1" ?
> 
> Given that the node names are significant, they should be enforced in
> the YAML schema.
> 
>> +
>> +properties:
>> +  compatible:
>> +    const: brcm,bcm2835-unicam
>> +
>> +  reg:
>> +    description:
>> +      physical base address and length of the register sets for the device.
> 
> This can be dropped.
> 
>> +    maxItems: 1
> 
> There are two items in the example below. How does this validate ?
> 
>> +
>> +  interrupts:
>> +    description: the IRQ line for this Unicam instance.
> 
> This can be dropped.
> 
>> +    maxItems: 1
>> +
>> +  clocks:
>> +    description: |-
>> +      list of clock specifiers, corresponding to entries in clock-names
>> +      property.
> 
>    clocks:
>      items:
>        - description: The clock for ...
>        - description: The clock for ...
> 
> (with the two descriptions matching the LP and VPU clocks, I don't know
> what they are).
> 
>> +
>> +  clock-names:
>> +    items:
>> +      - const: lp
>> +      - const: vpu
>> +
>> +  port:
>> +    $ref: /schemas/graph.yaml#/properties/port
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - interrupts
>> +  - clocks
>> +  - clock-names
>> +  - port
>> +
>> +additionalProperties: False
>> +
>> +examples:
>> +  - |
>> +    csi1: csi1@7e801000 {
>> +        compatible = "brcm,bcm2835-unicam";
>> +        reg = <0x7e801000 0x800>,
>> +              <0x7e802004 0x4>;
>> +        interrupts = <2 7>;
> 
> Let's use the Pi 4 device tree as an example, as that's what we're
> upstreaming first.
> 
>> +        clocks = <&clocks BCM2835_CLOCK_CAM1>,
> 
> This will fail to compile without a proper #include, did you get this to
> pass validation ?
> 
>> +                 <&firmware_clocks 4>;
>> +        clock-names = "lp", "vpu";
>> +        port {
>> +                csi1_ep: endpoint {
>> +                        remote-endpoint = <&tc358743_0>;
>> +                        data-lanes = <1 2>;
>> +                };
>> +        };
>> +    };
>> +
>> +    i2c0: i2c@7e205000 {
>> +        tc358743: csi-hdmi-bridge@0f {
>> +            compatible = "toshiba,tc358743";
>> +            reg = <0x0f>;
>> +            clocks = <&tc358743_clk>;
>> +            clock-names = "refclk";
>> +
>> +            tc358743_clk: bridge-clk {
>> +                    compatible = "fixed-clock";
>> +                    #clock-cells = <0>;
>> +                    clock-frequency = <27000000>;
>> +            };
>> +
>> +            port {
>> +                    tc358743_0: endpoint {
>> +                            remote-endpoint = <&csi1_ep>;
>> +                            clock-lanes = <0>;
>> +                            data-lanes = <1 2>;
>> +                            clock-noncontinuous;
>> +                            link-frequencies =
>> +                                /bits/ 64 <297000000>;
>> +                    };
>> +            };
>> +        };
>> +    };
> 
> I'd drop this node completely.
> 
>> +...
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 33f75892f98e..07f238fd5ff9 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -3679,6 +3679,12 @@ F:	Documentation/media/v4l-drivers/bcm2835-isp.rst
>>   F:	drivers/staging/vc04_services/bcm2835-isp
>>   F:	include/uapi/linux/bcm2835-isp.h
>>   
>> +BROADCOM BCM2835 CAMERA DRIVER
>> +M:	Raspberry Pi Kernel Maintenance <kernel-list@raspberrypi.com>
>> +L:	linux-media@vger.kernel.org
>> +S:	Maintained
>> +F:	Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml
>> +
>>   BROADCOM BCM47XX MIPS ARCHITECTURE
>>   M:	Hauke Mehrtens <hauke@hauke-m.de>
>>   M:	Rafał Miłecki <zajec5@gmail.com>
>