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Date: Mon, 16 Nov 2020 09:19:49 +0800 From: Can Guo <cang@...eaurora.org> To: Bart Van Assche <bvanassche@....org> Cc: asutoshd@...eaurora.org, nguyenb@...eaurora.org, hongwus@...eaurora.org, ziqichen@...eaurora.org, rnayak@...eaurora.org, linux-scsi@...r.kernel.org, kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com, Stanley Chu <stanley.chu@...iatek.com>, "James E.J. Bottomley" <jejb@...ux.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, Matthias Brugger <matthias.bgg@...il.com>, open list <linux-kernel@...r.kernel.org>, "moderated list:ARM/Mediatek SoC support" <linux-arm-kernel@...ts.infradead.org>, "moderated list:ARM/Mediatek SoC support" <linux-mediatek@...ts.infradead.org> Subject: Re: [PATCH RFC v1 1/1] scsi: pm: Leave runtime resume along if block layer PM is enabled Hi Bart, On 2020-11-15 04:57, Bart Van Assche wrote: > On 11/12/20 10:30 PM, Can Guo wrote: >> If block layer runtime PM is enabled for one SCSI device, then there >> is >> no need to forcibly change the SCSI device and its request queue's >> runtime >> PM status to active in scsi_dev_type_resume(), since block layer PM >> shall >> resume the SCSI device on the demand of bios. > > Please change "along" into "alone" in the subject of this patch (if > that > is what you meant). > Aha, sorry, a typo here. >> + if (scsi_is_sdev_device(dev)) { >> + struct scsi_device *sdev; >> >> + sdev = to_scsi_device(dev); > > A minor comment: I think that "struct scsi_device *sdev = > to_scsi_device(dev);" fits on a single line. > Sure. >> + * If block layer runtime PM is enabled for the SCSI device, >> + * let block layer PM handle its runtime PM routines. > > Please change "its runtime PM routines" into "runtime resume" or > similar. I think that will make the comment more clear. > Yes, thanks. >> + if (sdev->request_queue->dev) >> + return err; >> + } > > The 'dev' member only exists in struct request_queue if CONFIG_PM=y so > the above won't compile if CONFIG_PM=n. How about adding a function in > include/linux/blk-pm.h to check whether or not runtime PM has been > enabled? > You are right. > Otherwise this patch looks good to me. Actually, I am thinking about removing all the pm_runtime_set_active() codes in both scsi_bus_resume_common() and scsi_dev_type_resume() - we don't need to forcibly set the runtime PM status to RPM_ACTIVE for either SCSI host/target or SCSI devices. Whenever we access one SCSI device, either block layer or somewhere in the path (e.g. throgh sg IOCTL, sg_open() calls scsi_autopm_get_device()) should runtime resume the device first, and the runtime PM framework makes sure device's gets resumed as well. Thus, the pm_runtime_set_active() seems redundant. What do you think? Thanks, Can Guo. > > Thanks, > > Bart.
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