RE: [PATCH 07/11] dt-bindings: spi: spi-nxp-fspi: add a new property nxp,fspi-dll-slvdly

[Han Xu <han.xu@xxxxxxx>]

>-----Original Message-----
>From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
>Sent: Tuesday, July 5, 2022 5:37 AM
>To: Bough Chen <haibo.chen@xxxxxxx>; ashish.kumar@xxxxxxx;
>yogeshgaur.83@xxxxxxxxx; broonie@xxxxxxxxxx; robh+dt@xxxxxxxxxx;
>krzysztof.kozlowski+dt@xxxxxxxxxx; Han Xu <han.xu@xxxxxxx>;
>singh.kuldeep87k@xxxxxxxxx; tudor.ambarus@xxxxxxxxxxxxx; p.yadav@xxxxxx;
>michael@xxxxxxxx; miquel.raynal@xxxxxxxxxxx; richard@xxxxxx; vigneshr@xxxxxx;
>shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx
>Cc: linux-spi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
>devicetree@xxxxxxxxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; festevam@xxxxxxxxx;
>dl-linux-imx <linux-imx@xxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
>zhengxunli@xxxxxxxxxxx
>Subject: Re: [PATCH 07/11] dt-bindings: spi: spi-nxp-fspi: add a new property
>nxp,fspi-dll-slvdly
>
>On 05/07/2022 12:28, Bough Chen wrote:
>>> -----Original Message-----
>>> From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
>>> Sent: 2022年7月5日 17:48
>>> To: Bough Chen <haibo.chen@xxxxxxx>; ashish.kumar@xxxxxxx;
>>> yogeshgaur.83@xxxxxxxxx; broonie@xxxxxxxxxx; robh+dt@xxxxxxxxxx;
>>> krzysztof.kozlowski+dt@xxxxxxxxxx; Han Xu <han.xu@xxxxxxx>;
>>> singh.kuldeep87k@xxxxxxxxx; tudor.ambarus@xxxxxxxxxxxxx;
>>> p.yadav@xxxxxx; michael@xxxxxxxx; miquel.raynal@xxxxxxxxxxx;
>>> richard@xxxxxx; vigneshr@xxxxxx; shawnguo@xxxxxxxxxx;
>>> s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx
>>> Cc: linux-spi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
>>> devicetree@xxxxxxxxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx;
>>> festevam@xxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>;
>>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; zhengxunli@xxxxxxxxxxx
>>> Subject: Re: [PATCH 07/11] dt-bindings: spi: spi-nxp-fspi: add a new
>>> property nxp,fspi-dll-slvdly
>>>
>>> On 05/07/2022 11:11, haibo.chen@xxxxxxx wrote:
>>>> From: Haibo Chen <haibo.chen@xxxxxxx>
>>>>
>>>> Add one optional property nxp,fspi-dll-slvdly
>>>>
>>>> Signed-off-by: Haibo Chen <haibo.chen@xxxxxxx>
>>>> ---
>>>>  Documentation/devicetree/bindings/spi/spi-nxp-fspi.yaml | 6 ++++++
>>>>  1 file changed, 6 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/spi/spi-nxp-fspi.yaml
>>> b/Documentation/devicetree/bindings/spi/spi-nxp-fspi.yaml
>>>> index 1b552c298277..6bd61565686a 100644
>>>> --- a/Documentation/devicetree/bindings/spi/spi-nxp-fspi.yaml
>>>> +++ b/Documentation/devicetree/bindings/spi/spi-nxp-fspi.yaml
>>>> @@ -45,6 +45,12 @@ properties:
>>>>        - const: fspi_en
>>>>        - const: fspi
>>>>
>>>> +  nxp,fspi-dll-slvdly:
>>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>>> +    description: |
>>>> +      Specify the DLL slave line delay value.
>>>
>>> What are the units?
>>
>> Do you mean here need to give more detail explain about this properity?
>>
>> How about change like this?
>>    Specify the DLL slave line delay value. The delay target for slave delay line is:
>((nxp,fspi-dll-slvdly+1) * 1/32 * clock cycle of reference clock (serial root clock).
>
>This would be good.
>
>> The range of this value is 0~16.
>
>This needs to go to schema instead as "maximum: 16".
>
>But still the question is - what are the units used in this "delay"? ms? us?

HI Krzysztof,

According to the formula, the range should be 0~15, 16 should do nothing or no delay.

The unit should be clock phase. In other words, the delay can be in range of 1/32~1/2 clock cycle.


>
>Best regards,
>Krzysztof