linux-kernel - Re: [PATCH] PCI / PM: Don't runtime suspend when device only supports wakeup from D0

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190522185339.pfo5xeopyz2i5iem@wunner.de>
Date:   Wed, 22 May 2019 20:53:39 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Kai Heng Feng <kai.heng.feng@...onical.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        linux-pci@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH] PCI / PM: Don't runtime suspend when device only
 supports wakeup from D0

On Wed, May 22, 2019 at 02:39:56PM -0400, Alan Stern wrote:
> According to Kai, PME signalling doesn't work in D0 -- or at least, it
> is _documented_ not to work in D0 -- even though it is enabled and the
> device claims to support it.
> 
> In any case, I don't really see any point in "runtime suspending" a 
> device while leaving it in D0.  We might as well just leave it alone.

There may be devices whose drivers are able to reduce power consumption
through some device-specific means when runtime suspending, even though
the device remains in PCI_D0.  The patch would cause a power regression
for those.

In particular, pci_target_state() returns PCI_D0 if the device lacks the
PM capability.

Thanks,

Lukas