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Subject: Re: [PATCH v6 1/6] scsi: ufs: Add "wb_on" sysfs node to control WB
 on/off
From:   Bean Huo <huobean@gmail.com>
To:     Adrian Hunter <adrian.hunter@intel.com>, alim.akhtar@samsung.com,
        avri.altman@wdc.com, asutoshd@codeaurora.org, jejb@linux.ibm.com,
        martin.petersen@oracle.com, stanley.chu@mediatek.com,
        beanhuo@micron.com, bvanassche@acm.org, tomas.winkler@intel.com,
        cang@codeaurora.org
Cc:     linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Tue, 19 Jan 2021 17:31:45 +0100
In-Reply-To: <9ad2cf1a-68df-47ef-9fe7-01954d2d6181@intel.com>
References: <20210118201039.2398-1-huobean@gmail.com>
         <20210118201039.2398-2-huobean@gmail.com>
         <0a9971aa-e508-2aaa-1379-fb898471a252@intel.com>
         <fabf0e83387f6155efea521a15b00bb1225d35a4.camel@gmail.com>
         <9ad2cf1a-68df-47ef-9fe7-01954d2d6181@intel.com>
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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