Hi Jacopo,
On 16/03/2020 20:27, Jacopo Mondi wrote:
> The MAX9286 chip exposes registers to control the reverse channel
> amplitude signal. The channel amplitude has to be configured according
> to the connected remote serializer settings, in order to guarantee
> reliable communications.
>
> Serializer might be pre-programmed and initialize with their reverse
> channel noise threshold level increased. While this is intended to
> increase the signal/noise immunity ratio on the channel, the
> deserializer should be initialized accordingly, with its channel
> amplitude increased to 170mV.
>
> Add to the bindings documentation a required property to allow DTS users
> to specify the initial setting of the deserializer reverse channel and
> accommodate different serializer models.
>
Same comments really as the other property, that these are highly
dependent upon the serializer which is connected, so I wonder if there's
a better way to describe that association / communication requirement.
> Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> ---
> .../bindings/media/i2c/maxim,max9286.yaml | 21 +++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
> index ee8e0418b3f0..a1c56734a727 100644
> --- a/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
> +++ b/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
> @@ -54,6 +54,25 @@ properties:
> allOf:
> - $ref: /schemas/types.yaml#/definitions/uint32
>
> + maxim,reverse-channel-amplitude:
> + description: |
> + The reverse channel amplitude initial value, in milliVolts. If the remote
Should there be a newline after milliVolts. ? That seems like a brief,
followed by a description but all flowing together?
> + serializer is pre-programmed with an high reverse channel noise threshold,
/an/a/
> + the deserializer channel amplitude shall initially be increased to 170mV
> + to allow the two to communicate reliably. Likewise, if the remote
> + serializer probes without an increased reverse channel noise threshold,
> + the deserializer initial reverse channel amplitude should be set to 100mV
> + to be later increased to 170mV after serializers have increased their
/after/after the/
> + reverse channel noise threshold.
> + maxItems: 1
> + allOf:
> + - $ref: /schemas/types.yaml#/definitions/uint32
> + # The property can be easily expanded to support more values if needed,
> + # but that's what's supported today by the driver.
Stating "that's what's supported today" seems a bit redundant...
> + oneOf:
> + - const: 100
> + - const: 170
> +
> ports:
> type: object
> description: |
> @@ -155,6 +174,7 @@ required:
> - compatible
> - reg
> - maxim,overlap-window
> + - maxim,reverse-channel-amplitude
> - ports
> - i2c-mux
>
> @@ -177,6 +197,7 @@ examples:
> poc-supply = <&camera_poc_12v>;
> enable-gpios = <&gpio 13 GPIO_ACTIVE_HIGH>;
> maxim,overlap-window = MAX9286_OVLP_WINDOW_DISABLED;
> + maxim,reverse-channel-amplitude = <170>;
>
> ports {
> #address-cells = <1>;
>
