linux-kernel - Re: [PATCH] dt-bindings: serial: 8250: allow "main" and "uart" as clock names

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Message-ID: <79fde2dc-2370-4ec8-94eb-57715cfc2806@riscstar.com>
Date: Tue, 29 Jul 2025 16:35:57 -0500
From: Alex Elder <elder@...cstar.com>
To: Conor Dooley <conor@...nel.org>
Cc: Yixun Lan <dlan@...too.org>, gregkh@...uxfoundation.org,
 jirislaby@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, matthias.bgg@...il.com,
 angelogioacchino.delregno@...labora.com, lkundrak@...sk,
 devicetree@...r.kernel.org, linux-serial@...r.kernel.org,
 spacemit@...ts.linux.dev, linux-mediatek@...ts.infradead.org,
 linux-riscv@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] dt-bindings: serial: 8250: allow "main" and "uart" as
 clock names

On 7/29/25 4:08 PM, Conor Dooley wrote:
> On Tue, Jul 29, 2025 at 04:04:05PM -0500, Alex Elder wrote:
>> On 7/29/25 12:54 PM, Conor Dooley wrote:
>>> On Tue, Jul 29, 2025 at 06:53:19AM +0800, Yixun Lan wrote:
>>>> Hi Alex,
>>>>
>>>> On 17:00 Mon 28 Jul     , Alex Elder wrote:
>>>>> There are two compatible strings defined in "8250.yaml" that require
>>>>> two clocks to be specified, along with their names:
>>>>>     - "spacemit,k1-uart", used in "spacemit/k1.dtsi"
>>>>>     - "nxp,lpc1850-uart", used in "lpc/lpc18xx.dtsi"
>>>>>
>>>>> When only one clock is used, the name is not required.  However there
>>>>> are two places that do specify a name:
>>>>>     - In "mediatek/mt7623.dtsi", the clock for the "mediatek,mtk-btif"
>>>>>       compatible serial device is named "main"
>>>>>     - In "qca/ar9132.dtsi", the clock for the "ns8250" compatible
>>>>>       serial device is named "uart"
>>>>>
>>>>> In commit d2db0d7815444 ("dt-bindings: serial: 8250: allow clock 'uartclk'
>>>>> and 'reg' for nxp,lpc1850-uart"), Frank Li added the restriction that two
>>>>> named clocks be used for the NXP platform mentioned above.  Extend that
>>>>> so that the two named clocks used by the SpacemiT platform are similarly
>>>>> restricted.
>>>>>
>>>>> Add "main" and "uart" as allowed names when a single clock is specified.
>>>>>
>>>>> Fixes: 2c0594f9f0629 ("dt-bindings: serial: 8250: support an optional second clock")
>>>>> Reported-by: kernel test robot <lkp@...el.com>
>>>>> Closes: https://lore.kernel.org/oe-kbuild-all/202507160314.wrC51lXX-lkp@intel.com/
>>>>> Signed-off-by: Alex Elder <elder@...cstar.com>
>>>>> ---
>>>>>    .../devicetree/bindings/serial/8250.yaml      | 19 ++++++++++++++-----
>>>>>    1 file changed, 14 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/serial/8250.yaml b/Documentation/devicetree/bindings/serial/8250.yaml
>>>>> index e46bee8d25bf0..cef52ebd8f7da 100644
>>>>> --- a/Documentation/devicetree/bindings/serial/8250.yaml
>>>>> +++ b/Documentation/devicetree/bindings/serial/8250.yaml
>>>>> @@ -61,11 +61,17 @@ allOf:
>>>>>                - const: uartclk
>>>>>                - const: reg
>>>> ..
>>>>>        else:
>>>> would it be better to drop this 'else', and moving following 'if' block
>>>> to the same level with "nxp,lpc1850-uart"?
>>>>
>>>> the reason here would avoid too many indentions if add more constraint in
>>>> the future if other SoC uart need different clock-names..
>>>
>>> I agree, it's more typical to do it that way I think to boot.
>>>
>>> Also, why is there a k1/lpc conditional bit that is not part of the
>>> allOf in addition to the bits in the allOf? Can that get merged with the
>>> allOf please?
>>
>> Are you talking about the blank line here?
> 
> No, I'm talking about what's down around line 270 in the binding.

Oh wow that's in a weird spot, and it might be redundant?

Anyway I'll work on getting that fixed too before I send
my next version.

					-Alex

>>
>>      then:
>>        oneOf:
>>          - required: [ clock-frequency ]
>>          - required: [ clocks ]
>>                             <------ this blank line
>>    - if:
>>        properties:
>>          compatible:
>>            contains:
>>              const: nxp,lpc1850-uart
>>      then:
>>
>> I didn't notice that before.  It got inserted with commit
>> d2db0d7815444 ("dt-bindings: serial: 8250: allow clock
>> 'uartclk' and 'reg' for nxp,lpc1850-uart").
>>
>> If so, yes I'll remove that as well when I update the patch to
>> get rid of the else as Yixun suggests.
>>
>> Greg won't take this for a couple weeks so I'll hold off sending
>> v2 for a while.
>>
>> 					-Alex
>>