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

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Date:   Tue, 15 Feb 2022 15:03:25 +0900
From:   "Kiwoong Kim" <kwmad.kim@...sung.com>
To:     "'Bart Van Assche'" <bvanassche@....org>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <alim.akhtar@...sung.com>, <avri.altman@....com>,
        <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>,
        <beanhuo@...ron.com>, <cang@...eaurora.org>,
        <adrian.hunter@...el.com>, <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.

> > -	down_read(&hba->clk_scaling_lock);
> > +	if (ufshcd_is_clkscaling_supported(hba))
> > +		down_read(&hba->clk_scaling_lock);
> >
> >   	lrbp = &hba->lrb[tag];
> >   	WARN_ON(lrbp->cmd);
> 
> I don't like this patch at all. This patch makes testing the UFS driver
> more complicated without having any clear benefit. Additionally, adding
> if-statements in front of locking makes static source code analysis harder
> and is an anti-pattern. Please don't do this.
> 
> Bart. 

The benefit that I think is not blocking dev cmd during submitting a scsi cmd.
Rather, I don't understand why this lock is required if a SoC doesn't support clk scaling.

The period of ringing doorbells has been already protected by spin lock.

Thanks.
Kiwoong Kim