linux-kernel - Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB on/off

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Date:   Tue, 22 Dec 2020 22:08:56 +0100
From:   Bean Huo <huobean@...il.com>
To:     Stanley Chu <stanley.chu@...iatek.com>
Cc:     alim.akhtar@...sung.com, avri.altman@....com,
        asutoshd@...eaurora.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, beanhuo@...ron.com, bvanassche@....org,
        tomas.winkler@...el.com, cang@...eaurora.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB
 on/off

On Tue, 2020-12-22 at 21:50 +0100, Bean Huo wrote:
> > 
> > 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

seems there are only auto_hibern8 and wb will issue command to UFS
device. if you think auto_hibern8 also needs this protection.

I will add in the next version patch, otherwise, just add this checkup
in the WB.

Look forward to your feedback!

Thanks,
Bean