Re: [PATCH V2 1/2] dt-bindings: serial: add Broadcom's BCMBCA family High Speed UART

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 22/11/2023 19:39, William Zhang wrote:
> Hi,
> 
> On 11/22/2023 07:52 AM, Rafał Miłecki wrote:
>> On 22.11.2023 16:50, Krzysztof Kozlowski wrote:
>>> On 22/11/2023 16:49, Rafał Miłecki wrote:
>>>>>> For example a year ago I added binding for BCMBCA SoC timer without
>>>>>> actual driver, see e112f2de151b ("dt-bindings: timer: Add Broadcom's
>>>>>> BCMBCA timers").
>>>>>>
>>>>>> I'm not sure if we're going to agree on this, but personally I like
>>>>>> describing hardware as much as I can. So it's well documented /
>>>>>> understood and people may eventually write drivers for it. Maybe it's
>>>>>> partially because I come from Broadcom's world that isn't well known
>>>>>> for upstream efforts in general.
>>>>>
>>>>> The problem is that "brcm,bcmbca-hs-uart" is not describing 
>>>>> hardware. It
>>>>> is saying that all these devices have similar (compatible) programming
>>>>> model, so the OS can use just one compatible. This goes away from pure
>>>>> hardware description into interpretation.
>>>>>
> It is the same hardware IP block used in bcmbca SoCs.  To me, it 
> perfectly describe the hardware IP block and it does not need fallback 
> because there is no fallback.  We did that for SPI controller although 
> it has two revisions of that IP block so we have brcm,bcmbca-hsspi-v1.0 
> and 1.1
> 
>>>>> Rob already commented on such non-SoC compatibles multiple times. I do
>>>>> not see any reason here to not use specific compatible as fallback.
>>>>
> Sorry I missed Rob's comments.  If we have any new rule or notes about 
> this, I would like to check it out.
> 
>>>> Do I get it right we should rather have some base specific compatible
>>>> like: "brcm,bcm63138-hs-uart" and then if anything use fallback to it
>>>> like: "brcm,bcm4908-hs-uart", "brcm,bcm63138-hs-uart"; ?
>>>
>>> Yes, or the other way around, depends which is probably the oldest.
> If we absolutely can not use bcmbca-hs-uart, I would suggest to use 

We can, but I am surprised that you want without any driver. What's the
point of generic compatible?

> bcm63xx-hs-uart to be more soc specific and in fact the oldest SoC have 

What is xx? Wildcard? I mean... ehhh...

Best regards,
Krzysztof