linux-kernel - Re: [PATCH v4 2/3] dt-bindings: clock: si5351: add PLL reset mode property

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Message-ID: <20231017192859.GA2544830-robh@kernel.org>
Date:   Tue, 17 Oct 2023 14:28:59 -0500
From:   Rob Herring <robh@...nel.org>
To:     Alvin Šipraga <alvin@...s.dk>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Rabeeh Khoury <rabeeh@...id-run.com>,
        Jacob Siverskog <jacob@...nage.engineering>,
        Sergej Sawazki <sergej@...dac.com>, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/3] dt-bindings: clock: si5351: add PLL reset mode
 property

On Sat, Oct 14, 2023 at 08:19:42PM +0200, Alvin Šipraga wrote:
> From: Alvin Šipraga <alsi@...g-olufsen.dk>
> 
> For applications where the PLL must be adjusted without glitches in the
> clock output(s), a new silabs,pll-reset-mode property is added. It
> can be used to specify whether or not the PLL should be reset after
> adjustment. Resetting is known to cause glitches.
> 
> For compatibility with older device trees, it must be assumed that the
> default PLL reset mode is to unconditionally reset after adjustment.
> 
> Cc: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
> Cc: Rabeeh Khoury <rabeeh@...id-run.com>
> Cc: Jacob Siverskog <jacob@...nage.engineering>
> Cc: Sergej Sawazki <sergej@...dac.com>
> Signed-off-by: Alvin Šipraga <alsi@...g-olufsen.dk>
> ---
>  .../devicetree/bindings/clock/silabs,si5351.yaml   | 24 ++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/clock/silabs,si5351.yaml b/Documentation/devicetree/bindings/clock/silabs,si5351.yaml
> index 16d1142c4a2f..9621b534f30e 100644
> --- a/Documentation/devicetree/bindings/clock/silabs,si5351.yaml
> +++ b/Documentation/devicetree/bindings/clock/silabs,si5351.yaml
> @@ -60,6 +60,27 @@ properties:
>          - description: PLL source, XTAL (0) or CLKIN (1, Si5351C only).
>            enum: [ 0, 1 ]
>  
> +  silabs,pll-reset-mode:
> +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
> +    minItems: 1

If there's only 2 PLLs, then the maximum is 2 entries, right? So 
'maxItems: 2' in addition.

> +    description: |

Don't need '|'

> +      A list of cell pairs containing a PLL index and its reset mode.
> +    items:
> +      items:
> +        - description: PLL A (0) or PLL B (1)
> +          enum: [ 0, 1 ]
> +        - description: |
> +            Reset mode for the PLL. Mode can be one of:
> +
> +                0 - reset whenever PLL rate is adjusted (default mode)
> +                1 - do not reset when PLL rate is adjusted
> +
> +            In mode 1, the PLL is only reset if the silabs,pll-reset is
> +            specified in one of the clock output child nodes that also sources
> +            the PLL. This mode may be preferable if output clocks are expected
> +            to be adjusted without glitches.
> +          enum: [ 0, 1 ]
> +
>  patternProperties:
>    "^clkout@[0-7]$":
>      type: object
> @@ -199,6 +220,9 @@ examples:
>          /* Use XTAL input as source of PLL0 and PLL1 */
>          silabs,pll-source = <0 0>, <1 0>;
>  
> +        /* Don't reset PLL1 on rate adjustment */
> +        silabs,pll-reset-mode = <1 1>;
> +
>          /*
>           * Overwrite CLK0 configuration with:
>           * - 8 mA output drive strength
> 
> -- 
> 2.42.0
>