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

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Message-ID: <5c3f9f10-6a9d-45b4-80c0-09402b35bf47@riscstar.com>
Date: Tue, 29 Jul 2025 16:04:05 -0500
From: Alex Elder <elder@...cstar.com>
To: Conor Dooley <conor@...nel.org>, Yixun Lan <dlan@...too.org>
Cc: 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 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?

     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