linux-kernel - Re: [PATCH] ASoC: fsl_esai: Add pm runtime function

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Date:   Thu, 18 Apr 2019 11:12:45 +0000
From:   "S.j. Wang" <shengjiu.wang@....com>
To:     Mark Brown <broonie@...nel.org>
CC:     Nicolin Chen <nicoleotsuka@...il.com>,
        "timur@...nel.org" <timur@...nel.org>,
        "Xiubo.Lee@...il.com" <Xiubo.Lee@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: fsl_esai: Add pm runtime function

Hi

> On Thu, Apr 18, 2019 at 10:15:24AM +0000, S.j. Wang wrote:
> > > On Thu, Apr 18, 2019 at 02:00:12AM -0700, Nicolin Chen wrote:
> > > > On Thu, Apr 18, 2019 at 03:29:09AM +0000, S.j. Wang wrote:
> 
> > > > Just for curiosity, we had similar situation on imx6sx, so we
> > > > added suspend/resume with regcache. Why will the clock enable
> > > > state be lost too? Does CCM on imx8 (might not be called CCM
> > > > though) have any difference? What about clock rate settings?
> 
> > > That sounds like a bug somewhere else - I'd expect that after resume
> > > the clocking would be restored to the state it was in before suspend.
> 
> > There is limitation in our internal design. That is in imx8 the power
> > of subsystem will be disabled at suspend, include the clock state , clock
> rate.
> 
> Right, that's fairly normal but usually it'd be restored as part of the resume
> process?
> 
> > This patch is to enable the pm runtime,  so I think it is better to
> > move the clock operation to pm runtime,  and close the clock at
> > suspend to reduce the power.
> 
> It's definitely good to turn the clock off as much as possible, yes.

Thanks, will send v2.

Best regards
Wang shengjiu