linux-kernel - Re: [PATCH v2 1/6] dt-bindings: pwm: amlogic: fix s4 bindings

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Date:   Sun, 19 Nov 2023 10:04:22 -0600
From:   Rob Herring <robh@...nel.org>
To:     Jerome Brunet <jbrunet@...libre.com>
Cc:     Conor Dooley <conor+dt@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        devicetree@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org,
        Kevin Hilman <khilman@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        JunYi Zhao <junyi.zhao@...ogic.com>
Subject: Re: [PATCH v2 1/6] dt-bindings: pwm: amlogic: fix s4 bindings


On Fri, 17 Nov 2023 13:59:11 +0100, Jerome Brunet wrote:
> s4 has been added to the compatible list while converting the Amlogic PWM
> binding documentation from txt to yaml.
> 
> However, on the s4, the clock bindings have different meaning compared to
> the previous SoCs.
> 
> On the previous SoCs the clock bindings used to describe which input the
> PWM channel multiplexer should pick among its possible parents.
> 
> This is very much tied to the driver implementation, instead of describing
> the HW for what it is. When support for the Amlogic PWM was first added,
> how to deal with clocks through DT was not as clear as it nowadays.
> The Linux driver now ignores this DT setting, but still relies on the
> hard-coded list of clock sources.
> 
> On the s4, the input multiplexer is gone. The clock bindings actually
> describe the clock as it exists, not a setting. The property has a
> different meaning, even if it is still 2 clocks and it would pass the check
> when support is actually added.
> 
> Also the s4 cannot work if the clocks are not provided, so the property no
> longer optional.
> 
> Finally, for once it makes sense to see the input as being numbered
> somehow. No need to bother with clock-names on the s4 type of PWM.
> 
> Fixes: 43a1c4ff3977 ("dt-bindings: pwm: Convert Amlogic Meson PWM binding")
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> ---
>  .../devicetree/bindings/pwm/pwm-amlogic.yaml  | 69 ++++++++++++++++---
>  1 file changed, 60 insertions(+), 9 deletions(-)
> 

Reviewed-by: Rob Herring <robh@...nel.org>