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Thu, 20 Feb 2020 05:30:50 -0800 Received: from MTKMBS02N1.mediatek.inc (172.21.101.77) by MTKMBS62DR.mediatek.inc (172.29.94.18) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Thu, 20 Feb 2020 05:30:48 -0800 Received: from mtkcas08.mediatek.inc (172.21.101.126) by mtkmbs02n1.mediatek.inc (172.21.101.77) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Thu, 20 Feb 2020 21:28:54 +0800 Received: from [172.21.84.99] (172.21.84.99) by mtkcas08.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Thu, 20 Feb 2020 21:31:13 +0800 Message-ID: <1582205440.26304.50.camel@mtksdccf07> Subject: Re: [PATCH v1 1/2] scsi: ufs: add required delay after gating reference clock From: Stanley Chu To: Can Guo Date: Thu, 20 Feb 2020 21:30:40 +0800 In-Reply-To: References: <20200217093559.16830-1-stanley.chu@mediatek.com> <20200217093559.16830-2-stanley.chu@mediatek.com> <1581945168.26304.4.camel@mtksdccf07> <1581946449.26304.15.camel@mtksdccf07> <56c1fc80919491d058d904fcc7301835@codeaurora.org> <1582103495.26304.42.camel@mtksdccf07> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200220_053056_583042_F8B828F7 X-CRM114-Status: GOOD ( 21.10 ) 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: chun-hung.wu@mediatek.com, linux-scsi@vger.kernel.org, martin.petersen@oracle.com, andy.teng@mediatek.com, jejb@linux.ibm.com, peter.wang@mediatek.com, kuohong.wang@mediatek.com, linux-kernel@vger.kernel.org, avri.altman@wdc.com, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org, alim.akhtar@samsung.com, matthias.bgg@gmail.com, beanhuo@micron.com, bvanassche@acm.org, hongwus@codeaurora.org, Asutosh Das 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 Wed, 2020-02-19 at 18:33 +0800, Can Guo wrote: > Hi Stanley, > > On 2020-02-19 17:11, Stanley Chu wrote: > > Hi Can, > > > > On Wed, 2020-02-19 at 10:35 +0800, Can Guo wrote: > > > >> Since we all need this delay here, how about put the delay in the > >> entrence of ufshcd_setup_clocks(), before vops_setup_clocks()? > >> If so, we can remove all the delays we added in our vops since the > >> delay anyways delays everything inside ufshcd_setup_clocks(). > >> > > > > Always putting the delay in the entrance of ufshcd_setup_clocks() may > > add unwanted delay for vendors, just like your current implementation, > > or some other vendors who do not want to disable the reference clock. > > > > I think current patch is more reasonable because the delay is applied > > to > > clock only named as "ref_clk" specifically. > > > > If you needs to keep "ref_clk" in DT, would you consider to remove the > > delay in your ufs_qcom_dev_ref_clk_ctrl() and let the delay happens via > > common ufshcd_setup_clocks() only? However you may still need delay if > > call path comes from ufs_qcom_pwr_change_notify(). > > > > What do you think? > > > > I agree current change is more reasonable from what it looks, but the > fact > is that I canont remove the delay in ufs_qcom_dev_ref_clk_ctrl() even > with > this change. On our platforms, ref_clk in DT serves multipule purposes, > the ref_clk provided to UFS device is actually controlled in > ufs_qcom_dev_ref_clk_ctrl(), which comes before where this change kicks > start, > so if I remove the delay in ufs_qcom_dev_ref_clk_ctrl(), this change > cannot > provide us the correct delay before gate the ref_clk provided to UFS > device. > > Always putting the delay in the entrance of ufshcd_setup_clocks() may > > add unwanted delay for vendors, just like your current implementation, > > or some other vendors who do not want to disable the reference clock. > > I meant if we put the delay in the entrance, I will be able to remove > the delay in ufs_qcom_dev_ref_clk_ctrl(). Meanwhile, we can add proper > checks before the delay to make sure it is initiated only if ref_clk > needs > to be disabled, i.e: > > if(!on && !skip_ref_clk && hba->dev_info.clk_gating_wait_us) > usleep_range(); > > Does this look better to you? Firstly thanks so much for above details. Again this statement may also add unwanted delay if some other vendors does not have "ref_clk" in DT or they don't/can't disable the reference clock provided to UFS device. > > Anyways, we will see regressions with this change on our platforms, can > we > have more discussions before get it merged? It should be OK if you go > with > patch #2 alone first, right? Thanks. Now the fact is that this change will impact your flow and it seems no solid conclusion yet. Sure I could drop patch #1 and submit patch #2 only first : ) Thanks, Stanley Chu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel