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

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Message-ID: <015701d823d6$7a9e5540$6fdaffc0$@samsung.com>
Date:   Thu, 17 Feb 2022 17:15:09 +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.

> On 2/14/22 22:03, Kiwoong Kim wrote:
> > The benefit that I think is not blocking dev cmd during submitting a
> scsi cmd.
> 
> Hi Kiwoong,
> 
> Both ufshcd_exec_dev_cmd() and previous versions of
> ufshcd_queuecommand() obtain a reader lock on the clock scaling lock so
> concurrent submission of both command types is allowed. I'm not aware of
> any version of the UFS driver that serializes device commands against SCSI
> commands.
> 
> Additionally, please take a look at commit 8d077ede48c1 ("scsi: ufs:
> Optimize the command queueing code"). That patch removes the clock scaling
> lock from ufshcd_queuecommand().
> 
> Thanks,
> 
> Bart.

Okay, I got it.