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Mon, 30 Dec 2019 23:51:33 -0800 Received: from MTKMBS02N2.mediatek.inc (172.21.101.101) by MTKMBS62N1.mediatek.inc (172.29.193.41) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Mon, 30 Dec 2019 23:45:16 -0800 Received: from MTKCAS06.mediatek.inc (172.21.101.30) by mtkmbs02n2.mediatek.inc (172.21.101.101) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Tue, 31 Dec 2019 15:44:06 +0800 Received: from [172.21.77.33] (172.21.77.33) by MTKCAS06.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Tue, 31 Dec 2019 15:43:33 +0800 Message-ID: <1577778290.13164.45.camel@mtkswgap22> Subject: Re: [PATCH v1 1/2] scsi: ufs: set device as default active power mode during initialization only From: Stanley Chu To: Can Guo Date: Tue, 31 Dec 2019 15:44:50 +0800 In-Reply-To: <1577766179.13164.24.camel@mtkswgap22> References: <1577693546-7598-1-git-send-email-stanley.chu@mediatek.com> <1577693546-7598-2-git-send-email-stanley.chu@mediatek.com> <1577754469.13164.5.camel@mtkswgap22> <836772092daffd8283a97d633e59fc34@codeaurora.org> <1577766179.13164.24.camel@mtkswgap22> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-TM-SNTS-SMTP: 45FB1168EF4BF48378D8C06BB302A9DF542A4E7C9858C67C2092FB067919067B2000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191230_235144_387904_344DC4F3 X-CRM114-Status: GOOD ( 15.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: martin.petersen@oracle.com, linux-scsi@vger.kernel.org, andy.teng@mediatek.com, jejb@linux.ibm.com, chun-hung.wu@mediatek.com, kuohong.wang@mediatek.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, asutoshd@codeaurora.org, avri.altman@wdc.com, linux-mediatek@lists.infradead.org, peter.wang@mediatek.com, linux-scsi-owner@vger.kernel.org, subhashj@codeaurora.org, alim.akhtar@samsung.com, beanhuo@micron.com, pedrom.sousa@synopsys.com, bvanassche@acm.org, linux-arm-kernel@lists.infradead.org, matthias.bgg@gmail.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Can, On Tue, 2019-12-31 at 12:22 +0800, Stanley Chu wrote: > Hi Can, > > > > Hi Stanley, > > > > I see skipping ufshcd_set_ufs_dev_active() in ufshcd_probe_hba() > > if it is called from ufshcd_resume() path is the purpose here. > > > > If so, then ufshcd_set_dev_pwr_mode() would be called, meaning > > SSU command will be sent. Why is this SSU command needed to be > > sent after a full host reset and restore? Is ufshcd_probe_hba() > > not enough to make UFS device fully functional? > > After resume (for both runtime resume and system resume), device power > mode shall be back to "Active" to service incoming requests. > > I see two cases need device power mode transition during resume flow > 1. Device Power Mode = Sleep > 2. Device Power Mode = PowerDown > > For 1, ufshcd_probe_hba() is not invoked during resume flow, > hba->curr_dev_pwr_mode = SLEEP, thus ufshcd_resume() can invoke > ufshcd_set_dev_pwr_mode() to change device power mode. > > For 2, ufshcd_probe_hba() is invoked during resume flow, before this > fix, hba->curr_dev_pwr_mode will be set to ACTIVE (note that only this > flag is set as ACTIVE, but device may be still in PowerDown state if > device power is not fully shutdown or device HW reset is not executed > before resume), in the end, ufshcd_resume() will not invoke > ufshcd_set_dev_pwr_mode() to send SSU command to make device change back > to Active power mode. > > But if device is fully reset before resume (not by current mainstream > driver), device can be already in "Active" power mode after power on > again during resume flow. In this case, it is OK to set > hba->curr_dev_pwr_mode as ACTIVE in ufshcd_probe_hba() and SSU command > is not necessary. > > Thanks, > Stanley I think currently the assumption in ufshcd_probe_hba() that "device shall be already in Active power mode" makes sense because many device commands will be sent to device in ufshcd_probe_hba() but device is not promised to handle those commands in PowerDown power mode according to UFS spec. So, maybe always ensuring device being Active power mode before leaving ufshcd_probe_hba() is more reasonable. If so, I will drop this patch first. Thanks so much for your reviews. Happy new year! Thanks, Stanley _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel