linux-kernel - Re: [Update][PATCH v2 01/12] PM / core: Add NEVER_SKIP and SMART

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Message-ID: <9928366.cAI691llHG@aspire.rjw.lan>
Date:   Fri, 20 Oct 2017 13:28:33 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Lukas Wunner <lukas@...ner.de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Alan Stern <stern@...land.harvard.edu>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Documentation <linux-doc@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kevin Hilman <khilman@...nel.org>,
        Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
        Lee Jones <lee.jones@...aro.org>
Subject: Re: [Update][PATCH v2 01/12] PM / core: Add NEVER_SKIP and SMART_PREPARE driver flags

On Friday, October 20, 2017 1:35:27 PM CEST Greg Kroah-Hartman wrote:
> On Fri, Oct 20, 2017 at 01:11:22PM +0200, Rafael J. Wysocki wrote:
> > On Thursday, October 19, 2017 9:33:15 AM CEST Greg Kroah-Hartman wrote:
> > > On Thu, Oct 19, 2017 at 01:17:31AM +0200, Rafael J. Wysocki wrote:
> > > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > 
> > > > The motivation for this change is to provide a way to work around
> > > > a problem with the direct-complete mechanism used for avoiding
> > > > system suspend/resume handling for devices in runtime suspend.
> > > > 
> > > > The problem is that some middle layer code (the PCI bus type and
> > > > the ACPI PM domain in particular) returns positive values from its
> > > > system suspend ->prepare callbacks regardless of whether the driver's
> > > > ->prepare returns a positive value or 0, which effectively prevents
> > > > drivers from being able to control the direct-complete feature.
> > > > Some drivers need that control, however, and the PCI bus type has
> > > > grown its own flag to deal with this issue, but since it is not
> > > > limited to PCI, it is better to address it by adding driver flags at
> > > > the core level.
> > > > 
> > > > To that end, add a driver_flags field to struct dev_pm_info for flags
> > > > that can be set by device drivers at the probe time to inform the PM
> > > > core and/or bus types, PM domains and so on on the capabilities and/or
> > > > preferences of device drivers.  Also add two static inline helpers
> > > > for setting that field and testing it against a given set of flags
> > > > and make the driver core clear it automatically on driver remove
> > > > and probe failures.
> > > > 
> > > > Define and document two PM driver flags related to the direct-
> > > > complete feature: NEVER_SKIP and SMART_PREPARE that can be used,
> > > > respectively, to indicate to the PM core that the direct-complete
> > > > mechanism should never be used for the device and to inform the
> > > > middle layer code (bus types, PM domains etc) that it can only
> > > > request the PM core to use the direct-complete mechanism for
> > > > the device (by returning a positive value from its ->prepare
> > > > callback) if it also has been requested by the driver.
> > > > 
> > > > While at it, make the core check pm_runtime_suspended() when
> > > > setting power.direct_complete so that it doesn't need to be
> > > > checked by ->prepare callbacks.
> > > > 
> > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > 
> > > Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > Thanks!
> > 
> > Does it also apply to the other patches in the series?
> > 
> > I'd like to queue up the core patches for 4.15 as they are specifically
> > designed to only affect the drivers that actually set the flags, so there
> > shouldn't be any regression resulting from them, and I'd like to be
> > able to start using the flags in drivers going forward.
> 
> Yes, sorry, I thought I acked them, but you are right, I didn't:
> 
> Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> for all of them please.

Thanks!