linux-kernel - Re: [PATCH 7/9] dt-bindings: spi: mtk-snfi: add two timing delay property

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Date:   Wed, 30 Nov 2022 09:35:04 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Xiangsheng Hou (侯祥胜) 
        <Xiangsheng.Hou@...iatek.com>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "gch981213@...il.com" <gch981213@...il.com>,
        "vigneshr@...com" <vigneshr@...com>,
        "richard@....at" <richard@....at>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Benliang Zhao (赵本亮) 
        <Benliang.Zhao@...iatek.com>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Bin Zhang (章斌) <bin.zhang@...iatek.com>
Subject: Re: [PATCH 7/9] dt-bindings: spi: mtk-snfi: add two timing delay
 property

On 30/11/2022 09:18, Xiangsheng Hou (侯祥胜) wrote:
> Hi Krzysztof,
> 
> On Tue, 2022-11-29 at 08:47 +0100, Krzysztof Kozlowski wrote:
>> On 29/11/2022 03:50, Xiangsheng Hou (侯祥胜) wrote:
>>
>>>>> --- a/Documentation/devicetree/bindings/spi/mediatek,spi-mtk-
>>>>> snfi.yaml
>>>>> +++ b/Documentation/devicetree/bindings/spi/mediatek,spi-mtk-
>>>>> snfi.yaml
>>>>> @@ -55,6 +55,22 @@ properties:
>>>>>      description: device-tree node of the accompanying ECC
>>>>> engine.
>>>>>      $ref: /schemas/types.yaml#/definitions/phandle
>>>>>  
>>>>> +  rx-sample-delay:
>>>>
>>>> No, use existing property, don't invent your own stuff - missing
>>>> unit
>>>> suffix. See spi-peripheral-props.yaml.
>>>
>>> Will change to other private property. The read sample delay with
>>> MediaTek SPI NAND controller can be set with values from 0 to 47.
>>> However, it`s difficult to say the unit of each vaule, because the
>>> unit
>>> value will be difference with different chip process or different
>>> corner IC.
>>
>> Why you cannot use same formula as other SPI drivers for sample-
>> delay?
>> And divide/multiple by some factor specific to SoC, which is taken
>> from
>> driver_data?
> 
> Even for specific SoC, the unit of sample delay may be various with
> different corner IC.

Which is easy to achieve with driver_data as I said.

> Besides, whether it`s acceptable by change the property rx-sample-delay 
> and rx-latch-latency to mediatek,rx-sample-delay and mediatek,rx-latch-
> latency?

Not for sample delay, because you should use existing properties. Your
driver implementation is not usually argument to duplicate properties in
the bindings.

Best regards,
Krzysztof