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Message-ID: <4c15956660bd7305b0c095603bfa0e30c7f1610e.camel@gmail.com>
Subject: Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB
 on/off
From:   Bean Huo <huobean@gmail.com>
To:     Stanley Chu <stanley.chu@mediatek.com>
Cc:     alim.akhtar@samsung.com, avri.altman@wdc.com,
        asutoshd@codeaurora.org, jejb@linux.ibm.com,
        martin.petersen@oracle.com, beanhuo@micron.com, bvanassche@acm.org,
        tomas.winkler@intel.com, cang@codeaurora.org,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Tue, 22 Dec 2020 21:50:49 +0100
In-Reply-To: <1608617307.14045.3.camel@mtkswgap22>
References: <20201215230519.15158-1-huobean@gmail.com>
         <20201215230519.15158-2-huobean@gmail.com>
         <1608617307.14045.3.camel@mtkswgap22>
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On Tue, 2020-12-22 at 14:08 +0800, Stanley Chu wrote:
> > +     if (kstrtouint(buf, 0, &wb_enable))
> > +             return -EINVAL;
> > +
> > +     if (wb_enable != 0 && wb_enable != 1)
> > +             return -EINVAL;
> > +
> > +     pm_runtime_get_sync(hba->dev);
> > +     res = ufshcd_wb_ctrl(hba, wb_enable);
> 
> May this operation race with UFS shutdown flow?
> 
> To be more clear, ufshcd_wb_ctrl() here may be executed after host
> clock
> is disabled by shutdown flow?
> 
> If yes, we need to avoid it.
> 
> Thanks,
> Stanley Chu

Yes, it is quite possible, but who will mess up this on purpose?

ok, to counterbalance our concerns, I can add checkup:


/* UFS device & link must be active before we change WB status */
if (!ufshcd_is_ufs_dev_active(hba) || !ufshcd_is_link_active(hba))
	return -EINVAL;


how do you think about?

Bean