linux-kernel - Re: [PATCH v2 2/9] dt-bindings: spi: zynqmp-qspi: Add example dual upper/lower bus

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Message-ID: <2588bb7f-2a3a-4001-ab1b-6d9bd57b545b@baylibre.com>
Date: Wed, 18 Jun 2025 13:27:35 -0500
From: David Lechner <dlechner@...libre.com>
To: Sean Anderson <sean.anderson@...ux.dev>, Mark Brown <broonie@...nel.org>,
 Michal Simek <michal.simek@....com>, linux-spi@...r.kernel.org
Cc: Jinjie Ruan <ruanjinjie@...wei.com>,
 Miquel Raynal <miquel.raynal@...tlin.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>,
 Conor Dooley <conor+dt@...nel.org>, Krzysztof Kozlowski
 <krzk+dt@...nel.org>, Rob Herring <robh@...nel.org>,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/9] dt-bindings: spi: zynqmp-qspi: Add example dual
 upper/lower bus

On 6/16/25 5:00 PM, Sean Anderson wrote:
> Add an example of the spi-buses property showcasing how to have devices
> on both the upper and lower buses.
> 
> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
> ---
> 
> Changes in v2:
> - New
> 
>  .../bindings/spi/spi-zynqmp-qspi.yaml         | 22 ++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml b/Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml
> index 02cf1314367b..c6a57fbb9dcf 100644
> --- a/Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml
> +++ b/Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml


In addition to changing the example, we could also extend the
spi-buses property for this controller since we know this controller
has 2 buses.

  properties:
    ...

    spi-buses:
      description: 0 is the "lower" bus, 1 is the "upper" bus
      maxItems: 2
      items:
        enum: [0, 1]

Not sure what to do about the default though since as discussed elsewhere,
this controller needs the default bus number to be the CS number for
backwards compatibility rather than `default: [0]` as is specified in the
previous patch.

I suppose we could leave default out of the generic binding and leave it
up to each individual controller to decide how to handle that.

> @@ -69,7 +69,7 @@ examples:
>        #address-cells = <2>;
>        #size-cells = <2>;
>  
> -      qspi: spi@...f0000 {
> +      qspi: spi-controller@...f0000 {

It seems more common to have spi@ rather than spi-controller@.
Is there a push to change this in general?

>          compatible = "xlnx,zynqmp-qspi-1.0";
>          clocks = <&zynqmp_clk 53>, <&zynqmp_clk 82>;
>          clock-names = "ref_clk", "pclk";