linux-kernel - Re: [PATCH] clk: sunxi-ng: v3s: add support for variable rate audio pll output

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Message-ID: <C1E55B65-370F-4875-B7D6-7CD7A82A91DD@aosc.io>
Date:   Thu, 18 Feb 2021 16:04:03 +0800
From:   Icenowy Zheng <icenowy@...c.io>
To:     Maxime Ripard <maxime@...no.tech>,
        Tobias Schramm <t.schramm@...jaro.org>
CC:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: sunxi-ng: v3s: add support for variable rate audio pll output



于 2021年2月18日 GMT+08:00 下午3:58:35, Maxime Ripard <maxime@...no.tech> 写到:
>Hi,
>
>On Fri, Feb 12, 2021 at 02:57:25PM +0100, Tobias Schramm wrote:
>> Previously the variable rate audio pll output was fixed to a divider
>of
>> four. This is unfortunately incompatible with generating commonly
>used
>> I2S core clock rates like 24.576MHz from the 24MHz parent clock.
>> This commit adds support for arbitrary audio pll output dividers to
>fix
>> that.
>> 
>> Signed-off-by: Tobias Schramm <t.schramm@...jaro.org>
>
>It's not really clear to me how that would help.

We have introducee SDM-based accurate audio PLL on several
other SoCs. Some people is quite sensitive about audio-related things.

>
>The closest frequency we can provide for 24.576MHz would be 24580645
>Hz,
>with N = 127, M = 31 and P = 4, so it would work with what we have
>already?
>
>Maxime