linux-kernel - Re: [PATCH v6 1/6] scsi: ufs: Add "wb_on" sysfs node to control WB on/off

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Message-ID: <0fb16957375cc5916b61aa6ea2c13c64455f1d35.camel@gmail.com>
Date:   Tue, 19 Jan 2021 17:31:45 +0100
From:   Bean Huo <huobean@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>, alim.akhtar@...sung.com,
        avri.altman@....com, asutoshd@...eaurora.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, stanley.chu@...iatek.com,
        beanhuo@...ron.com, bvanassche@....org, tomas.winkler@...el.com,
        cang@...eaurora.org
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/6] scsi: ufs: Add "wb_on" sysfs node to control WB
 on/off

On Tue, 2021-01-19 at 12:00 +0200, Adrian Hunter wrote:
> > > Is it so, that after a full reset, WB is always enabled again? 
> > > Is
> > > that
> > > intended?
> > 
> > Hello Adrian
> > Good questions. yes, after a full reset, the UFS device side by
> > default
> > is wb disabled,  then WB will be always enabled agaion in
> > ufshcd_wb_config(hba). but, for the platform which
> > supports UFSHCD_CAP_CLK_SCALING, wb will be disabled again while
> > clk
> > scaling down and enabled while clk scaling up.
> > 
> > Regarding the last question, I think OEM wants to do that. maybe
> > they
> > suppose there will be a lot of writing after reset?? From the UFS
> > device's point of view, the control of WB is up to the user.
> 
> If it is by design enabled after reset, then perhaps it should be
> mentioned
> in the sysfs documentation.

ok, will add it in the next version.

thanks,
Bean