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

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Message-ID: <CAJX_Q+3AcDOYHTJJFRa=rxAWiycDXo99_2KuLSmg5+f4upPJDQ@mail.gmail.com>
Date:   Fri, 23 Jun 2023 08:51:25 +0100
From:   Lucas Tanure <tanure@...ux.com>
To:     neil.armstrong@...aro.org
Cc:     Conor Dooley <conor.dooley@...rochip.com>,
        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 Thu, Jun 22, 2023 at 10:38 AM Neil Armstrong
<neil.armstrong@...aro.org> wrote:
>
> 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.
No, there is not an AO_uart in T7, as far as I can see from the code
and datasheet.

>
> 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 ?
As S4 and T7 are the same as g12a, I thought it would be better to
just have g12a uart.
But sure, I can use S4 as fallback.

>
> +      - 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....
Ok, v5 is coming up.
>
> 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
> >>
>