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

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Message-ID: <20250729-clench-hastily-b80f11f73336@spud>
Date: Tue, 29 Jul 2025 22:08:58 +0100
From: Conor Dooley <conor@...nel.org>
To: Alex Elder <elder@...cstar.com>
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 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.

> 
>     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
> 

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