linux-kernel - Re: [PATCH] regmap: mmio: prepare/unprepare clk only when read/write

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Message-ID: <20200423104000.GD4808@sirena.org.uk>
Date:   Thu, 23 Apr 2020 11:40:00 +0100
From:   Mark Brown <broonie@...nel.org>
To:     peng.fan@....com
Cc:     rafael@...nel.org, linux-kernel@...r.kernel.org, linux-imx@....com,
        shengjiu.wang@....com
Subject: Re: [PATCH] regmap: mmio: prepare/unprepare clk only when read/write

On Thu, Apr 23, 2020 at 01:46:31PM +0800, peng.fan@....com wrote:
> From: Peng Fan <peng.fan@....com>
> 
> use clk_prepare at the very beginning will invoke pm runtime resume,
> if the clk is binded with a power domain. This will cause runtime
> power high. Let's use clk_prepare_enable and clk_disable_unprepare
> when read/write to avoid the runtime power issue.

This will mean that we're doing clk_prepare() during I/O which isn't
good since for MMIO regmaps we support I/O operations in atomic
contexts.

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