linux-kernel - Re: [PATCH v4 2/3] dt-bindings: serial: amlogic,meson-uart: Add compatible string for T7

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Date:   Thu, 22 Jun 2023 11:38:49 +0200
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Conor Dooley <conor.dooley@...rochip.com>,
        Lucas Tanure <tanure@...ux.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        Kevin Hilman <khilman@...libre.com>, Nick <nick@...das.com>,
        Artem <art@...das.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Conor Dooley <conor@...nel.org>
Subject: Re: [PATCH v4 2/3] dt-bindings: serial: amlogic,meson-uart: Add
 compatible string for T7

On 22/06/2023 11:26, Conor Dooley wrote:
> Hey Lucas,
> 
> On Thu, Jun 22, 2023 at 09:40:44AM +0100, Lucas Tanure wrote:
>> Amlogic T7 SoCs uses the same UART controller as S4 SoCs and G12A.
>> There is no need for an extra compatible line in the driver, but
>> add T7 compatible line for documentation.
>>
>> Co-developed-by: Conor Dooley <conor@...nel.org>
> 
> You can delete this, I don't need a Co-developed-by tag for review
> feedback.
> 
>> Signed-off-by: Lucas Tanure <tanure@...ux.com>
>> ---
>>   .../devicetree/bindings/serial/amlogic,meson-uart.yaml      | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/serial/amlogic,meson-uart.yaml b/Documentation/devicetree/bindings/serial/amlogic,meson-uart.yaml
>> index 01ec45b3b406..4ca4673169aa 100644
>> --- a/Documentation/devicetree/bindings/serial/amlogic,meson-uart.yaml
>> +++ b/Documentation/devicetree/bindings/serial/amlogic,meson-uart.yaml
>> @@ -46,6 +46,12 @@ properties:
>>             - amlogic,meson8b-uart
>>             - amlogic,meson-gx-uart
>>             - amlogic,meson-s4-uart
>> +      - description: Everything-Else power domain UART controller on G12A compatible SoCs
> 
> s/Everything-Else/Always-on/


"Everything-Else" was the amlogic naming for the non-always-on power domain, but it seems
it's no more something used on new SoCs like the T7 family.

Anyway, the description is wrong, and it's a mess because we used "amlogic,meson-ao-uart"
for uarts on the Always-On domain, but here it's described as Everything-Else...

Lucas, is there AO_uarts on T7 ? if not drop this amlogic,meson-ao-uart for the T7 UARTs.

But if there's no more AO uart controller, you'll need to change drivers/tty/serial/meson_uart.c
and add a OF_EARLYCON_DECLARE() for amlogic,meson-t7-uart.

But still, why don't you use the amlogic,meson-s4-uart as fallback instead ?

+      - description: UART controller on T7 compatible SoCs
+        items:
+          - const: amlogic,meson-t7-uart
+          - const: amlogic,meson-s4-uart

and update meson_uart.c if there's no AO uarts anymore....

Neil

> Otherwise,
> Acked-by: Conor Dooley <conor.dooley@...rochip.com>
> 
> Perhaps it can be fixed on application, I don't know how the amlogic
> maintainers operate.
> 
> Cheers,
> Conor.
> 
>> +        items:
>> +          - enum:
>> +              - amlogic,meson-t7-uart
>> +          - const: amlogic,meson-g12a-uart
>> +          - const: amlogic,meson-ao-uart
>>         - description: Everything-Else power domain UART controller on G12A SoCs
>>           items:
>>             - const: amlogic,meson-g12a-uart
>> -- 
>> 2.41.0
>>