linux-kernel - Re: [PATCH v1 1/4] arm64: dts: ti: k3-am62x: Enable AUDIO

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Message-ID: <20230802133244.b66pg3mztotgqotm@steerable>
Date:   Wed, 2 Aug 2023 08:32:44 -0500
From:   Nishanth Menon <nm@...com>
To:     Francesco Dolcini <francesco@...cini.it>
CC:     Jai Luthra <j-luthra@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Francesco Dolcini <francesco.dolcini@...adex.com>
Subject: Re: [PATCH v1 1/4] arm64: dts: ti: k3-am62x: Enable AUDIO_REFCLKx

On 13:37-20230802, Francesco Dolcini wrote:
> 
> 
> Il 2 agosto 2023 13:23:50 CEST, Jai Luthra <j-luthra@...com> ha scritto:
> >Hi Francesco,
> >
> >Thank you for posting this patch.
> >
> >On Jul 31, 2023 at 16:21:32 +0200, Francesco Dolcini wrote:
> >> From: Jai Luthra <j-luthra@...com>
> >> 
> >> On AM62-based SoCs the AUDIO_REFCLKx clocks can be used as an input to
> >> external peripherals when configured through CTRL_MMR, so add the
> >> clock nodes.
> >> 
> >> Signed-off-by: Jai Luthra <j-luthra@...com>
> >> Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>
> >> ---
> >>  arch/arm64/boot/dts/ti/k3-am62-main.dtsi  | 18 ++++++++++++++++++
> >>  arch/arm64/boot/dts/ti/k3-am62a-main.dtsi | 18 ++++++++++++++++++
> >
> >Given currently none of the AM62A boards are using the refclks, can you 
> >drop those or just mark the nodes as disabled. Whoever is the first user 
> >can enable them.
> 
> I can drop the 2 clocks from AM62A, however, should we really do it? These clocks exist and they are just defined in the DTS, they are not going to be enabled if not used, "ti,am62-epwm-tbclk" is also not disabled for example.

Overall, the SoC clock as such has nothing to do with board specific, so
leave it default (enabled) in SoC.dts - just want to make sure that the
clk-parent selection doesn't get in the way of platforms and is a sane
default.

I find audio clock muxing a bit of a pain (only next to DSS clocking,
but that is another story).. so will depend on you folks for help.
Looking at https://software-dl.ti.com/tisci/esd/latest/5_soc_doc/am62ax/clocks.html#clocks-for-board0-device
and Clocking spec, setting this:
+			assigned-clocks = <&k3_clks 157 0>;
+			assigned-clock-parents = <&k3_clks 157 8>;
as default implies:
pll2_hsdiv8 output - which looks like the default mux value anyways.. I
am ok for it being explicit, but wondering if that works for boards that
do not use this default.

Could you guys confirm?

(sidenote): Fransesco - your new mail client has line wrap issues ;)
-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D