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[95.91.252.233]) by smtp.googlemail.com with ESMTPSA id i18sm17684002edt.68.2020.12.23.13.52.08 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Wed, 23 Dec 2020 13:52:08 -0800 (PST) Message-ID: <1fa9d66079d34768f16fb0ef8d8c46ceead7bff6.camel@gmail.com> Subject: Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB on/off From: Bean Huo To: Stanley Chu Cc: alim.akhtar@samsung.com, avri.altman@wdc.com, asutoshd@codeaurora.org, jejb@linux.ibm.com, martin.petersen@oracle.com, beanhuo@micron.com, bvanassche@acm.org, tomas.winkler@intel.com, cang@codeaurora.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 23 Dec 2020 22:52:07 +0100 In-Reply-To: <1608617307.14045.3.camel@mtkswgap22> References: <20201215230519.15158-1-huobean@gmail.com> <20201215230519.15158-2-huobean@gmail.com> <1608617307.14045.3.camel@mtkswgap22> 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, 2020-12-22 at 14:08 +0800, Stanley Chu wrote: > Hi Bean, > > On Wed, 2020-12-16 at 00:05 +0100, Bean Huo wrote: > > From: Bean Huo > > > > Currently UFS WriteBooster driver uses clock scaling up/down to set > > WB on/off, for the platform which doesn't support > > UFSHCD_CAP_CLK_SCALING, > > WB will be always on. Provide a sysfs attribute to enable/disable > > WB > > during runtime. Write 1/0 to "wb_on" sysfs node to enable/disable > > UFS WB. > > > > Reviewed-by: Avri Altman > > Reviewed-by: Stanley Chu > > Signed-off-by: Bean Huo > > --- > > drivers/scsi/ufs/ufs-sysfs.c | 41 > > ++++++++++++++++++++++++++++++++++++ > > drivers/scsi/ufs/ufshcd.c | 3 +-- > > drivers/scsi/ufs/ufshcd.h | 2 ++ > > 3 files changed, 44 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/scsi/ufs/ufs-sysfs.c b/drivers/scsi/ufs/ufs- > > sysfs.c > > index 08e72b7eef6a..f3ca3d6b82c4 100644 > > --- a/drivers/scsi/ufs/ufs-sysfs.c > > +++ b/drivers/scsi/ufs/ufs-sysfs.c > > @@ -189,6 +189,45 @@ static ssize_t auto_hibern8_store(struct > > device *dev, > > return count; > > } > > > > +static ssize_t wb_on_show(struct device *dev, struct > > device_attribute *attr, > > + char *buf) > > +{ > > + struct ufs_hba *hba = dev_get_drvdata(dev); > > + > > + return sysfs_emit(buf, "%d\n", hba->wb_enabled); > > +} > > + > > +static ssize_t wb_on_store(struct device *dev, struct > > device_attribute *attr, > > + const char *buf, size_t count) > > +{ > > + struct ufs_hba *hba = dev_get_drvdata(dev); > > + unsigned int wb_enable; > > + ssize_t res; > > + > > + if (ufshcd_is_clkscaling_supported(hba)) { > > + /* > > + * If the platform supports UFSHCD_CAP_CLK_SCALING, > > turn WB > > + * on/off will be done while clock scaling up/down. > > + */ > > + dev_warn(dev, "To control WB through wb_on is not > > allowed!\n"); > > + return -EOPNOTSUPP; > > + } > > + if (!ufshcd_is_wb_allowed(hba)) > > + return -EOPNOTSUPP; > > + > > + if (kstrtouint(buf, 0, &wb_enable)) > > + return -EINVAL; > > + > > + if (wb_enable != 0 && wb_enable != 1) > > + return -EINVAL; > > + > > + pm_runtime_get_sync(hba->dev); > > + res = ufshcd_wb_ctrl(hba, wb_enable); > > May this operation race with UFS shutdown flow? > > To be more clear, ufshcd_wb_ctrl() here may be executed after host > clock > is disabled by shutdown flow? > > If yes, we need to avoid it. > > Thanks, > Stanley Chu > Hi Stanley and Can I just sent a new patch to address this issue, let's discusss in that patch set, I added PM maintainer in the mail as well to help us address concern about pm_runtime_get_sync and shutdown flow. If that way can fix this issue, then I will update this patch again. one note: I didn't add "if (!ufshcd_is_ufs_dev_active(hba) || !ufshcd_is_link_active(hba))" checkup, since sysfs node access is a normal request as well, UFS driver should give correct response as possbile as it can, even if device/link is lower power mode. Thanks, Bean