All of lore.kernel.org
 help / color / mirror / Atom feed
From: Lukas Wunner <lukas@wunner.de>
To: Heiner Kallweit <hkallweit1@gmail.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	Bjorn Helgaas <helgaas@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Kai Heng Feng <kai.heng.feng@canonical.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Time to re-enable Runtime PM per default for PCI devcies?
Date: Mon, 4 Jan 2021 18:39:44 +0100	[thread overview]
Message-ID: <20210104173944.GA31187@wunner.de> (raw)
In-Reply-To: <4eb10092-e3f9-c9be-2dec-e6de8aeedf97@gmail.com>

On Thu, Dec 31, 2020 at 10:38:12AM +0100, Heiner Kallweit wrote:
> On 31.12.2020 05:07, Lukas Wunner wrote:
> > FWIW, if platform_pci_power_manageable() returns true, it can probably
> > be assumed that allowing runtime PM by default is okay.  So as a first
> > step, you may want to call that instead of adding a new callback.
> 
> I don't think that's sufficient. Most likely all the broken old systems
> return true for platform_pci_power_manageable().

platform_pci_power_manageable() is not a global flag, but rather
a per-device flag whether the platform is capable of power-managing
that device.  E.g. for the ACPI platform, it indicates that objects
such as _PS0 or _PS3 are present in the device's namespace.

My point is that if the platform can power-manage a device,
then it ought to be safe to enable runtime PM by default for it.

If you insist on a "big hammer" approach by turning on runtime PM
by default for everything, you risk regressions.  You can avoid
that by going for a smart approach which enables runtime PM in
cases when it's safe.

Thanks,

Lukas

  parent reply	other threads:[~2021-01-04 17:40 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-17 15:56 Time to re-enable Runtime PM per default for PCI devcies? Heiner Kallweit
2020-11-17 16:38 ` Bjorn Helgaas
2020-11-17 16:57   ` Rafael J. Wysocki
2020-12-26 15:26     ` Heiner Kallweit
2020-12-29 11:56       ` Kai-Heng Feng
2020-12-29 21:11         ` Heiner Kallweit
2020-12-30 22:56     ` Heiner Kallweit
2020-12-31  4:07       ` Lukas Wunner
2020-12-31  9:38         ` Heiner Kallweit
2020-12-31  9:52           ` Heiner Kallweit
2021-01-04 17:39           ` Lukas Wunner [this message]
2021-01-04 20:32             ` Heiner Kallweit
2020-12-29 11:30   ` Lukas Wunner

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210104173944.GA31187@wunner.de \
    --to=lukas@wunner.de \
    --cc=bhelgaas@google.com \
    --cc=helgaas@kernel.org \
    --cc=hkallweit1@gmail.com \
    --cc=kai.heng.feng@canonical.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=mika.westerberg@linux.intel.com \
    --cc=rafael@kernel.org \
    --cc=rjw@rjwysocki.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.