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

[William Zhang]

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 
bcm63xx-hs-uart to be more soc specific and in fact the oldest SoC have 
such IP is 63138.

> 
> Thank you for helping me on that!
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