linux-kernel - Re: Time to re-enable Runtime PM per default for PCI devcies?

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Date:   Tue, 29 Dec 2020 12:30:24 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Kai Heng Feng <kai.heng.feng@...onical.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Time to re-enable Runtime PM per default for PCI devcies?

> On Tue, Nov 17, 2020 at 04:56:09PM +0100, Heiner Kallweit wrote:
> > With Runtime PM disabled e.g. the PHY on network devices may remain
> > powered up even with no cable plugged in, affecting battery lifetime
> > on mobile devices. Currently we have to rely on the respective distro
> > or user to enable Runtime PM via sysfs (echo auto > power/control).
> > Some devices work around this restriction by calling pm_runtime_allow
> > in their probe routine, even though that's not recommended by
> > https://www.kernel.org/doc/Documentation/power/pci.txt
> > 
> > Disabling Runtime PM per default seems to be a big hammer, a quirk
> > for affected devices / systems may had been better. And we still
> > have the option to disable Runtime PM for selected devices via sysfs.

Removing the recommendation in pci.txt and allowing runtime PM in more
drivers by default seems sensible to me.  Such an incremental approach
is less risky with regards to regressions than a big hammer.  Heiner,
care to submit patches to that effect?

Thanks,

Lukas