linux-kernel - Re: [PATCH RFC v1 1/1] scsi: pm: Leave runtime resume along if block layer PM is enabled

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Message-ID: <6d774277-b055-6924-cf2d-01e874ac3f7b@acm.org>
Date:   Tue, 17 Nov 2020 20:38:11 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.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

On 11/15/20 5:42 PM, Can Guo wrote:
> 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 parent (and its parent's parent and so on)gets resumed as
> well.
> Thus, the pm_runtime_set_active() seems redundant. What do you think?

Hi Can,

It is not clear to me why the pm_runtime_set_active() calls occur in the
scsi_pm.c source file since the block layer automatically activates
block devices if necessary. Maybe these calls are a leftover from a time
when runtime suspended devices were not resumed automatically by the
block layer? Anyway, I'm fine with removing these calls.

Thanks,

Bart.