linux-kernel - RE: [PATCH v3 1/1] scsi: ufs: Enable block layer runtime PM for well-known logical units

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Message-ID: <SN6PR04MB464005D38551AFBCBBA72E2BFCCE0@SN6PR04MB4640.namprd04.prod.outlook.com>
Date:   Wed, 25 Mar 2020 23:18:59 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Can Guo <cang@...eaurora.org>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "nguyenb@...eaurora.org" <nguyenb@...eaurora.org>,
        "hongwus@...eaurora.org" <hongwus@...eaurora.org>,
        "rnayak@...eaurora.org" <rnayak@...eaurora.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "kernel-team@...roid.com" <kernel-team@...roid.com>,
        "saravanak@...gle.com" <saravanak@...gle.com>,
        "salyzyn@...gle.com" <salyzyn@...gle.com>
CC:     Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Bart Van Assche <bvanassche@....org>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        Tomas Winkler <tomas.winkler@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 1/1] scsi: ufs: Enable block layer runtime PM for
 well-known logical units

 
> 
> Block layer RPM is enabled for the genernal UFS SCSI devices when they are
> probed by their driver. However block layer RPM is not enabled for UFS
> well-known SCSI devices.
> 
> As UFS SCSI devices have their corresponding BSG char devices, accessing
> a BSG char device via IOCTL may send requests to its corresponding SCSI
> device through its request queue. If BSG IOCTL sends a request to a
> well-known SCSI device when hba is not runtime active, due to block layer
> RPM is not eanbled for the well-known SCSI devices, hba, which is at the
> top of a scsi device's parent chain, shall not be resumed, then unexpected
> error would happen.
> 
> This change enables block layer RPM for the well-known SCSI devices, so
> that block layer can handle RPM for the well-known SCSI devices just like
> for the general SCSI devices.
> 
> Signed-off-by: Can Guo <cang@...eaurora.org>
Reviewed-by: Avri Altman <avri.altman@....com>