linux-kernel - Re: [PATCH v1] riscv: dts: starfive: move timebase-frequency to .dtsi

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Date:   Sun, 3 Dec 2023 11:03:52 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Emil Renner Berthing <emil.renner.berthing@...onical.com>
Cc:     linux-riscv@...ts.infradead.org,
        Conor Dooley <conor.dooley@...rochip.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Walker Chen <walker.chen@...rfivetech.com>,
        JeeHeng Sia <jeeheng.sia@...rfivetech.com>,
        Leyfoon Tan <leyfoon.tan@...rfivetech.com>
Subject: Re: [PATCH v1] riscv: dts: starfive: move timebase-frequency to .dtsi

On Fri, Dec 01, 2023 at 02:44:58PM +0100, Emil Renner Berthing wrote:
> Conor Dooley wrote:
> > From: Conor Dooley <conor.dooley@...rochip.com>
> >
> > Properties fixed by the SoC should be defined in the $soc.dtsi, and the
> > timebase-frequency is not sourced directly from an off-chip oscillator.
> 
> Yes, according to the JH7100 docs[1] the mtime register is sourced from the
> osc_sys external oscillator through u74rtc_toggle. However I haven't yet found
> a place in the docs that describe where that clock is divided by 4 to get
> 6.25MHz from the 25MHz.
> 
> I expect the JH7110 mtime is set up in a similar way, but haven't yet dug into
> the available documentation.

Your other reply suggests that this is a fixed division for the jh7110,
in which case it makes sense to leave it as-is. mpfs is different in
that it is fixed to 1 MHz regardless of which of the permitted external
oscillator frequencies you use.

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