linux-kernel - Re: [PATCH 03/10] clk: mediatek: mux: add clk notifier functions

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Message-ID: <20220907225957.10541-1-miles.chen@mediatek.com>
Date:   Thu, 8 Sep 2022 06:59:57 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     <angelogioacchino.delregno@...labora.com>
CC:     <chun-jie.chen@...iatek.com>, <devicetree@...r.kernel.org>,
        <drinkcat@...omium.org>, <jose.exposito89@...il.com>,
        <krzysztof.kozlowski+dt@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <matthias.bgg@...il.com>,
        <miles.chen@...iatek.com>, <mturquette@...libre.com>,
        <nfraprado@...labora.com>, <rex-bc.chen@...iatek.com>,
        <robh+dt@...nel.org>, <sboyd@...nel.org>, <weiyi.lu@...iatek.com>,
        <wenst@...omium.org>
Subject: Re: [PATCH 03/10] clk: mediatek: mux: add clk notifier functions

> From: Chen-Yu Tsai <wenst@...omium.org>
> 
> With device frequency scaling, the mux clock that (indirectly) feeds the
> device selects between a dedicated PLL, and some other stable clocks.
> 
> When a clk rate change is requested, the (normally) upstream PLL is
> reconfigured. It's possible for the clock output of the PLL to become
> unstable during this process.
> 
> To avoid causing the device to glitch, the mux should temporarily be
> switched over to another "stable" clock during the PLL rate change.
> This is done with clk notifiers.
> 
> This patch adds common functions for notifiers to temporarily and
> transparently reparent mux clocks.
> 
> This was loosely based on commit 8adfb08605a9 ("clk: sunxi-ng: mux: Add
> clk notifier functions").
>

Reviewed-by: Miles Chen <miles.chen@...iatek.com>