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[95.91.238.27]) by smtp.googlemail.com with ESMTPSA id h12sm11297196ejx.81.2021.01.19.08.31.46 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 19 Jan 2021 08:31:47 -0800 (PST) Message-ID: <0fb16957375cc5916b61aa6ea2c13c64455f1d35.camel@gmail.com> Subject: Re: [PATCH v6 1/6] scsi: ufs: Add "wb_on" sysfs node to control WB on/off From: Bean Huo To: Adrian Hunter , 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> <9ad2cf1a-68df-47ef-9fe7-01954d2d6181@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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