linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Bjorn Helgaas <helgaas@kernel.org>
To: Lukas Wunner <lukas@wunner.de>
Cc: Konstantin Kharlamov <Hi-Angel@yandex.ru>,
	linux-pci@vger.kernel.org,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Andreas Noever <andreas.noever@gmail.com>,
	linux-pm@vger.kernel.org
Subject: Re: [PATCH] PCI: don't power-off apple thunderbolt controller on s2idle
Date: Fri, 7 May 2021 08:30:02 -0500	[thread overview]
Message-ID: <20210507133002.GA1499665@bjorn-Precision-5520> (raw)
In-Reply-To: <20210506220738.GA2150@wunner.de>

On Fri, May 07, 2021 at 12:07:38AM +0200, Lukas Wunner wrote:
> On Thu, May 06, 2021 at 04:48:42PM -0500, Bjorn Helgaas wrote:
> > On Thu, May 06, 2021 at 08:38:20PM +0300, Konstantin Kharlamov wrote:
> > > On Macbook 2013 resuming from s2idle results in external monitor no
> > > longer being detected, and dmesg having errors like:
> > > 
> > >     pcieport 0000:06:00.0: can't change power state from D3hot to D0 (config space inaccessible)
> > > 
> > > and a stacktrace. The reason turned out that the hw that the quirk
> > > powers off does not get powered on back on resume.
> > 
> > quirk_apple_poweroff_thunderbolt() was added in 2014 by 1df5172c5c25
> > ("PCI: Suspend/resume quirks for Apple thunderbolt").  It claims
> > "power is automatically restored before resume," so there must be
> > something special about s2idle that prevents the power-on.
> 
> With s2idle, the machine isn't suspended via ACPI, so the AML code
> which powers the controller off isn't executed.  The dance to prepare
> the controller for power-off consequently isn't necessary but rather
> harmful.
> 
> To get the same power savings as with ACPI suspend, the controller
> needs to be powered off via runtime suspend.  I posted patches for
> that back in 2016.  I'm using them on my laptop, they need some
> polishing and rebasing before I can repost them due to massive
> changes that have happened in the thunderbolt driver in the meantime.
> Without these patches, the controller sucks 1.5W of power in s2idle.
> 
> > Obviously the *hardware* hasn't changed since 1df5172c5c25.  Is s2idle
> > something that wasn't tested back then, or is this problem connected
> > to an s2idle change since then?  Can we identify a commit that
> > introduced this problem?  That would help with backporting or stable
> > tags.
> 
> Yes I believe the quirk predates the introduction of s2idle by a couple
> of years.

In an ideal world, we would know which commit introduced s2idle and
hence the possibility of hitting this bug, and we would add a Fixes:
tag for that commit so we could connect this fix with it.

Apart from that, what I don't like about this (and about the original
1df5172c5c25) is that there's no connection to a spec or to documented
behavior of the device or of suspend/resume.

For example, "With s2idle, the machine isn't suspended via ACPI, so
the AML code which powers the controller off isn't executed."  AFAICT
that isn't actually a required, documented property of s2idle, but
rather it reaches into the internal implementation.

The code comment "If suspend mode is s2idle, power won't get restored
on resume" is similar.  !pm_suspend_via_firmware() tells us that
platform firmware won't be invoked.  But the connection between *that*
and "power won't get restored" is unexplained.

> > > Signed-off-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> 
> Reviewed-by: Lukas Wunner <lukas@wunner.de>

Thanks for looking at this!

Bjorn

  parent reply	other threads:[~2021-05-07 13:30 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-06 17:38 [PATCH] PCI: don't power-off apple thunderbolt controller on s2idle Konstantin Kharlamov
2021-05-06 21:48 ` Bjorn Helgaas
2021-05-06 22:07   ` Lukas Wunner
2021-05-07  9:51     ` Rafael J. Wysocki
2021-05-08  8:48       ` Lukas Wunner
2021-05-07 13:30     ` Bjorn Helgaas [this message]
2021-05-07 14:08       ` Konstantin Kharlamov
2021-05-12 20:36         ` Konstantin Kharlamov
2021-05-17 19:51           ` PING " Konstantin Kharlamov
2021-05-19 17:28         ` Bjorn Helgaas
2021-05-19 19:12           ` Rafael J. Wysocki
2021-05-19 19:48             ` Bjorn Helgaas
2021-05-20 11:27               ` Rafael J. Wysocki
2021-05-20 11:54                 ` Rafael J. Wysocki
2021-05-20 19:49                   ` Bjorn Helgaas
2021-05-20 23:28                     ` Konstantin Kharlamov
2021-05-24  6:59                       ` Konstantin Kharlamov
2021-05-20 23:55                     ` [PATCH v2] PCI: don't call firmware hooks on suspend unless it's fw-controlled Konstantin Kharlamov
2021-05-28  7:39                       ` PING: " Konstantin Kharlamov
2021-06-03  8:36                         ` PING: " Konstantin Kharlamov
2021-06-03 17:46                           ` Bjorn Helgaas
2021-06-04  8:30                             ` Konstantin Kharlamov
2021-05-21  9:47                     ` [PATCH] PCI: don't power-off apple thunderbolt controller on s2idle Rafael J. Wysocki
2021-05-07 15:02       ` Rafael J. Wysocki
2021-05-08  8:20       ` Lukas Wunner
2021-05-07  9:32   ` Konstantin Kharlamov
2021-05-07 13:07     ` Bjorn Helgaas
2021-05-07 13:48       ` Konstantin Kharlamov
2021-05-20 11:58   ` Rafael J. Wysocki
2021-06-07 23:17 ` Bjorn Helgaas

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=20210507133002.GA1499665@bjorn-Precision-5520 \
    --to=helgaas@kernel.org \
    --cc=Hi-Angel@yandex.ru \
    --cc=andreas.noever@gmail.com \
    --cc=linux-pci@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=lukas@wunner.de \
    --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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).