linux-kernel - Re: [PATCH 1/1] thunderbolt: Prevent root port runtime suspend during NVM upgrade

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Message-ID: <20181126105951.GE2296@lahna.fi.intel.com>
Date:   Mon, 26 Nov 2018 12:59:51 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        Lukas Wunner <lukas@...ner.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] thunderbolt: Prevent root port runtime suspend
 during NVM upgrade

On Mon, Nov 26, 2018 at 11:46:39AM +0100, Greg Kroah-Hartman wrote:
> On Mon, Nov 26, 2018 at 12:47:46PM +0300, Mika Westerberg wrote:
> > During NVM upgrade process the host router is hot-removed for a short
> > while. During this time it is possible that the root port is moved into
> > D3cold which would be fine if the root port could trigger PME on itself.
> > However, many systems actually do not implement it so what happens is
> > that the root port goes into D3cold and never wakes up unless userspace
> > does PCI config space access, such as running 'lscpi'.
> > 
> > For this reason we explicitly prevent the root port from runtime
> > suspending during NVM upgrade.
> > 
> > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > ---
> >  drivers/thunderbolt/switch.c | 40 ++++++++++++++++++++++++++++++++++--
> >  1 file changed, 38 insertions(+), 2 deletions(-)
> 
> Is this a regression?  If so, should it go to stable kernels?

It is not a regression.

> If not, and this never worked, should this just wait until 4.21-rc1?

Only reason I would like to have it included in v4.20 is that v4.20
started supporting PCI runtime PM for these systems so NVM upgrade would
then not work until v4.21.

But I'm fine either way and can send it to you later for v4.21 inclusion :)