linux-kernel - Re: [PATCH v1] scsi: ufs: remove clk_scaling

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Date:   Tue, 15 Feb 2022 12:00:00 +0100
From:   Bean Huo <huobean@...il.com>
To:     Kiwoong Kim <kwmad.kim@...sung.com>,
        'Adrian Hunter' <adrian.hunter@...el.com>,
        'Avri Altman' <Avri.Altman@....com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        alim.akhtar@...sung.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, beanhuo@...ron.com,
        cang@...eaurora.org, sc.suh@...sung.com, hy50.seo@...sung.com,
        sh425.lee@...sung.com, bhoon95.kim@...sung.com,
        vkumar.1997@...sung.com
Subject: Re: [PATCH v1] scsi: ufs: remove clk_scaling_lock when clkscaling
 isn't supported.

On Sat, 2022-02-12 at 13:44 +0900, Kiwoong Kim wrote:
> > The error handler really should have exclusive access.  One of the
> > places
> > you change does explain that:
> > 
> >  		 * Hold the scaling lock just in case dev cmds
> >  		 * are sent via bsg and/or sysfs.
> >  		 */
> > -		down_write(&hba->clk_scaling_lock);
> > +		if (ufshcd_is_clkscaling_supported(hba))
> > +			down_write(&hba->clk_scaling_lock); 
> 
> Yeah.., I saw the comment but didn't get why.
> 
> Is there anyone who knows why it's necessary for all SoCs?
> At lease, I know there is no reason to forbid concurrent executions
> of dev cmd and power mode change.
> 
> If there's nothing, how about adding a quick to ignore it?
> 
> Thanks.
> Kiwoong Kim
> 

The name of clk_scaling_lock has explained everything, for the platform
which doesn't support load-based clk scaling, doesn't need to hold this
lock.

Acked-by: Bean Huo <beanhuo@...ron.com>