linux-kernel - Re: [PATCH v1 1/2] dt-bindings: dsp: mediatek: Add default clock sources for mt8186 dsp

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Message-ID: <1f0bb630-20b0-160e-a530-05fae7572b10@collabora.com>
Date:   Wed, 2 Nov 2022 10:13:14 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Tinghan Shen <tinghan.shen@...iatek.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Daniel Baluta <daniel.baluta@....com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Yaochun Hung <yc.hung@...iatek.com>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        sound-open-firmware@...a-project.org, alsa-devel@...a-project.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v1 1/2] dt-bindings: dsp: mediatek: Add default clock
 sources for mt8186 dsp

Il 01/11/22 07:11, Tinghan Shen ha scritto:
> Add the default clock sources used by mt8186 dsp.
> 
> Signed-off-by: Tinghan Shen <tinghan.shen@...iatek.com>
> ---
>   .../devicetree/bindings/dsp/mediatek,mt8186-dsp.yaml | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dsp/mediatek,mt8186-dsp.yaml b/Documentation/devicetree/bindings/dsp/mediatek,mt8186-dsp.yaml
> index 3e63f79890b4..4cc0634c876b 100644
> --- a/Documentation/devicetree/bindings/dsp/mediatek,mt8186-dsp.yaml
> +++ b/Documentation/devicetree/bindings/dsp/mediatek,mt8186-dsp.yaml
> @@ -35,11 +35,15 @@ properties:
>       items:
>         - description: mux for audio dsp clock
>         - description: mux for audio dsp local bus
> +      - description: default clock source for dsp local bus
> +      - description: default clock source for dsp core
>   
>     clock-names:
>       items:
>         - const: audiodsp
>         - const: adsp_bus
> +      - const: mainpll_d2_d2
> +      - const: clk26m
>   
>     power-domains:
>       maxItems: 1
> @@ -82,9 +86,11 @@ examples:
>                 <0x1068f000 0x1000>;
>           reg-names = "cfg", "sram", "sec", "bus";
>           clocks = <&topckgen CLK_TOP_AUDIODSP>,
> -                 <&topckgen CLK_TOP_ADSP_BUS>;
> -        clock-names = "audiodsp",
> -                      "adsp_bus";
> +                 <&topckgen CLK_TOP_ADSP_BUS>,
> +                 <&topckgen CLK_TOP_MAINPLL_D2_D2>,
> +                 <&clk26m>;
> +        clock-names = "audiodsp", "adsp_bus",
> +                      "mainpll_d2_d2", "clk26m";

You are assigning those clocks just to be able to call clk_set_parent() in
the DSP mt8186-clk driver... and that's not necessary, nor it is the best
way of doing what you're trying to.

In reality, you don't need to add new clocks and you don't need to manage
that into the driver, as you can simply assign clock parents in devicetree
... like:

assigned-clocks = <&topckgen CLK_TOP_AUDIODSP>, <&topckgen CLK_TOP_ADSP_BUS>;
assigned-clock-parents = <&clk26m>, <&topckgen CLK_TOP_MAINPLL_D2_D2>;

without any clk_set_parent() call in the driver.

When the driver will call clk_prepare_enable() for top_audiodsp and/or for
top_adsp_bus, the assigned parents' refcount will also be increased (and
if the parent clock is not enabled, the clk framework will enable it).

Regards,
Angelo