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Date: Wed, 31 May 2023 16:01:57 +0200
From: Tommaso Merciai <tomm.merciai@...il.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>,
jacopo.mondi@...asonboard.com, martin.hecht@...et.eu,
linuxfancy@...glegroups.com,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>,
Hans Verkuil <hverkuil@...all.nl>,
Marco Felsch <m.felsch@...gutronix.de>,
Gerald Loacker <gerald.loacker@...fvision.net>,
Krzysztof Hałasa <khalasa@...p.pl>,
Shawn Tu <shawnx.tu@...el.com>,
Linus Walleij <linus.walleij@...aro.org>,
Benjamin Mugnier <benjamin.mugnier@...s.st.com>,
Mikhail Rudenko <mike.rudenko@...il.com>,
Nicholas Roth <nicholas@...hemail.net>,
linux-media@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] media: dt-bindings: alvium: add document YAML
binding
Hi Laurent,
On Wed, May 31, 2023 at 02:06:00PM +0300, Laurent Pinchart wrote:
> Hi Tommaso,
>
> On Wed, May 31, 2023 at 12:20:47PM +0200, Tommaso Merciai wrote:
> > On Mon, May 29, 2023 at 09:43:26AM +0300, Laurent Pinchart wrote:
> > > On Mon, May 29, 2023 at 09:39:13AM +0300, Laurent Pinchart wrote:
> > > > On Sun, May 28, 2023 at 09:16:05PM +0000, Sakari Ailus wrote:
> > > > > On Fri, May 26, 2023 at 07:39:43PM +0200, Tommaso Merciai wrote:
> > > > > > Add documentation of device tree in YAML schema for the ALVIUM
> > > > > > Camera from Allied Vision Inc.
> > > > > >
> > > > > > References:
> > > > > > - https://www.alliedvision.com/en/products/embedded-vision-solutions
> > > > > >
> > > > > > Signed-off-by: Tommaso Merciai <tomm.merciai@...il.com>
> > > > > > ---
> > > > > > Changes since v1:
> > > > > > - Fixed build error as suggested by RHerring bot
> > > > > >
> > > > > > .../media/i2c/alliedvision,alvium.yaml | 115 ++++++++++++++++++
> > > > > > 1 file changed, 115 insertions(+)
> > > > > > create mode 100644 Documentation/devicetree/bindings/media/i2c/alliedvision,alvium.yaml
> > > > > >
> > > > > > diff --git a/Documentation/devicetree/bindings/media/i2c/alliedvision,alvium.yaml b/Documentation/devicetree/bindings/media/i2c/alliedvision,alvium.yaml
> > > > > > new file mode 100644
> > > > > > index 000000000000..81e9e560c99d
> > > > > > --- /dev/null
> > > > > > +++ b/Documentation/devicetree/bindings/media/i2c/alliedvision,alvium.yaml
> > > > > > @@ -0,0 +1,115 @@
> > > > > > +# SPDX-License-Identifier: GPL-2.0
> > > > > > +%YAML 1.2
> > > > > > +---
> > > > > > +$id: http://devicetree.org/schemas/media/i2c/alliedvision,alvium.yaml#
> > > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > > +
> > > > > > +title: Alliedvision Alvium Camera
> > > >
> > > > s/Alliedvision/Allied Vision/
> > > >
> > > > > > +
> > > > > > +maintainers:
> > > > > > + - Tommaso Merciai <tomm.merciai@...il.com>
> > > > > > + - Martin Hecht <martin.hecht@...et.eu>
> > > > > > +
> > > > > > +allOf:
> > > > > > + - $ref: /schemas/media/video-interface-devices.yaml#
> > > > > > +
> > > > > > +properties:
> > > > > > + compatible:
> > > > > > + const: alliedvision,alvium
> > > >
> > > > The name is very generic. There are Alvium camera modules that have a
> > > > GMSL or FPD-Link interface, and I'm pretty sure those will require a
> > > > different driver. I would add module-specific compatible strings (e.g.
> > > > "alliedvision,alvium-1500c", ...) here, with a generic fallback.
> > > > "alliedvision,alvium" isn't good as it won't cover GMSL or FPD-Link,
> > > > maybe "alliedvision,alvium-csi2" would be an option.
> > >
> > > Actually, "alvium-1500c" as a specific compatible string won't do. You
> > > need the exact model in the compatible string, otherwise it won't be
> > > possible for the driver to handle device-specific configuration (for
> > > instance accessing registers of the camera sensor for fine-grained
> > > configuration). I would thus recommend using "alliedvision,alvium-1500c"
> > > and "alliedvision,alvium-1800c" as generic fallbacks, along compatible
> > > strings that include the exact device model.
> >
> > Agree with alliedvision,alvium-csi2 and thanks for your suggestion.
> > In my opinion we don’t need names for 1500c and
> > others because the same driver can drive all the alvium models.
> > Alvium is taking care of different sensor abstractions.
> >
> > I test with this driver with the following models:
> >
> > - 1800 C-1240c
> > - 1800 C-040c
> > - 1500 C-500
> >
> > What do you think about?
>
> As far as I understand, the camera modules allow accessing sensors
> registers from the host (through the ISP) for fine-grained
> configuration. Even if that's not implemented in the driver at the
> moment, I think it's an important feature to eventually support, and it
> will require a way for the system to identify the camera module
> precisely, to know which sensor the module uses. That's why I would like
> that information to be available in DT, in the form of a compatible
> string. For instance,
>
> compatible = "alliedvision,alvium-1500c-1240c",
> "alliedvision,alvium-1500c";
>
> The driver will only need DT match entries for
> "alliedvision,alvium-1500c" and "alliedvision,alvium-1800c".
Thanks for your feedback.
Some clarification:
The Alvium doesn't allow direct access on the sensor.
Alvium hides the particular sensor totally.
For this reason I would prefer to keep generic
"alvium-csi2" name.
What do you think?
Thanks,
Tommaso
>
> > > > > > +
> > > > > > + reg:
> > > > > > + maxItems: 1
> > > > > > +
> > > > > > + clocks:
> > > > > > + description: XCLK Input Clock
> > > > > > +
> > > > > > + clock-names:
> > > > > > + const: xclk
> > > > >
> > > > > I'd also drop this as you have a single clock only: it's redundant.
> > > > >
> > > > > > +
> > > > > > + powerdown-gpios:
> > > > > > + maxItems: 1
> > > > > > + description: >
> > > > > > + Reference to the GPIO connected to the powerdown pin, if any.
> > > > > > +
> > > > > > + reset-gpios:
> > > > > > + maxItems: 1
> > > > > > + description: >
> > > > > > + Reference to the GPIO connected to the reset pin, if any.
> > > >
> > > > Reading the Alvium CSI-2 Cameras User Guide, I don't see any powerdown
> > > > or reset pin on the 22-pin connector. Am I missing something ? There are
> > > > however two GPIOs (in addition to the I2C signals that are also
> > > > documented as GPIOs), do you plan to support those ?
> > > >
> > > > > > +
> > > > > > + streamon-delay:
> > > > > > + maxItems: 1
> > > > > > + description: >
> > > > > > + Delay before camera start capturing frames in us.
> > > >
> > > > Add "-us" to the property name to indicate the unit.
> > > >
> > > > This is a vendor-specific property, and should thus have a vendor
> > > > prefix.
> > > >
> > > > A longer description is needed, from that single line I have no idea
> > > > what the property does exactly.
> > > >
> > > > > > +
> > > > > > + rotation:
> > > > > > + enum:
> > > > > > + - 0
> > > > > > + - 180
> > > >
> > > > Why is the rotation restricted to 0 or 180 ? Someone could mount the
> > > > module with 90 degrees rotation, shouldn't the DT bindings allow
> > > > describing that ?
> > > >
> > > > You need a property for the vcc-ext-in supply.
> > > >
> > > > > > +
> > > > > > + port:
> > > > > > + description: Digital Output Port
> > > > > > + $ref: /schemas/graph.yaml#/$defs/port-base
> > > > > > + additionalProperties: false
> > > > > > +
> > > > > > + properties:
> > > > > > + endpoint:
> > > > > > + $ref: /schemas/media/video-interfaces.yaml#
> > > > > > + unevaluatedProperties: false
> > > > > > +
> > > > > > + properties:
> > > > > > + clock-lanes:
> > > > > > + const: 0
> > > > >
> > > > > The driver can know this, no need to have it in DT, i.e. please drop it.
> > > > >
> > > > > > + data-lanes:
> > > > > > + minItems: 1
> > > > > > + maxItems: 4
> > > > > > + link-frequencies: true
> > > > > > +
> > > > > > + required:
> > > > > > + - data-lanes
> > > > > > + - link-frequencies
> > > > > > +
> > > > > > +required:
> > > > > > + - compatible
> > > > > > + - reg
> > > > > > + - clocks
> > > > > > + - clock-names
> > > > > > + - port
> > > > > > +
> > > > > > +additionalProperties: false
> > > > > > +
> > > > > > +examples:
> > > > > > + - |
> > > > > > + #include <dt-bindings/gpio/gpio.h>
> > > > > > + #include <dt-bindings/clock/imx8mp-clock.h>
> > > > > > +
> > > > > > + i2c {
> > > > > > + #address-cells = <1>;
> > > > > > + #size-cells = <0>;
> > > > > > +
> > > > > > + camera: alvium@3c {
> > > > > > + compatible = "alliedvision,alvium";
> > > >
> > > > The "alliedvision" prefix is missing from
> > > > Documentation/devicetree/bindings/vendor-prefixes.yaml.
> > > >
> > > > > > + pinctrl-names = "default";
> > > > > > + pinctrl-0 = <&pinctrl_csi0_pwn>, <&pinctrl_csi0_rst>, <&pinctrl_csi_mclk>;
> > > >
> > > > I'd drop pinctrl, it makes the example longer without adding much value.
> > > >
> > > > > > + reg = <0x3c>;
> > > > > > + clocks = <&clk IMX8MP_CLK_IPP_DO_CLKO2>;
> > > > > > + clock-names = "xclk";
> > > > > > + assigned-clocks = <&clk IMX8MP_CLK_IPP_DO_CLKO2>;
> > > > > > + assigned-clock-parents = <&clk IMX8MP_CLK_24M>;
> > > > > > + assigned-clock-rates = <24000000>;
> > > > > > + streamon-delay = <20>;
> > > > > > + powerdown-gpios = <&gpio2 11 GPIO_ACTIVE_HIGH>;
> > > > > > + reset-gpios = <&gpio1 6 GPIO_ACTIVE_LOW>;
> > > > > > + status = "okay";
> > > > > > +
> > > > > > + port {
> > > > > > + alvium_out: endpoint {
> > > > > > + remote-endpoint = <&mipi_csi_0_in>;
> > > > > > + data-lanes = <1 2 3 4>;
> > > > > > + link-frequencies = /bits/ 64 <681250000>;
> > > > > > + clock-lanes = <0>;
> > > > > > + };
> > > > > > + };
> > > > > > + };
> > > > > > + };
> > > > > > +
> > > > > > +...
>
> --
> Regards,
>
> Laurent Pinchart
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