linux-kernel - RE: [PATCH 1/2] clk: imx: pll14xx: use writel

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Message-ID: <AM0PR04MB44817EBFF8CF1BB6E2CE369D88760@AM0PR04MB4481.eurprd04.prod.outlook.com>
Date:   Wed, 13 Nov 2019 12:15:45 +0000
From:   Peng Fan <peng.fan@....com>
To:     Daniel Baluta <daniel.baluta@....com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        Abel Vesa <abel.vesa@....com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "festevam@...il.com" <festevam@...il.com>
CC:     dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Aisheng Dong <aisheng.dong@....com>,
        Alice Guo <alice.guo@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        Leonard Crestez <leonard.crestez@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "will@...nel.org" <will@...nel.org>
Subject: RE: [PATCH 1/2] clk: imx: pll14xx: use writel_relaxed

Hi Daniel,

> Subject: Re: [PATCH 1/2] clk: imx: pll14xx: use writel_relaxed
> 
> 
> On Wed, 2019-11-13 at 07:24 +0000, Peng Fan wrote:
> > From: Peng Fan <peng.fan@....com>
> >
> > It not make sense to use writel, use relaxed variant.
> >
> 
> Hi Peng,
> 
> Please explain why this change is needed.

writel has a barrier, however that barrier is not needed,
because device memory access is in order and clk driver
has spin_lock or other lock to make sure write finished.

I would hear more comments before I post V2 about
the change and other similar patches to switch to
use relaxed API.

Thanks,
Peng.