linux-kernel - Re: [PATCH] Revert "ARM: cns3xxx: pci: avoid potential stack overflow"

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Date:	Thu, 9 Jun 2016 12:01:56 -0500
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Krzysztof Hałasa <khalasa@...p.pl>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "ARM: cns3xxx: pci: avoid potential stack
 overflow"

On Wed, Jun 01, 2016 at 11:09:47PM +0200, Arnd Bergmann wrote:
> On Wednesday, June 1, 2016 1:08:59 PM CEST Krzysztof Hałasa wrote:
> > Bjorn Helgaas <bhelgaas@...gle.com> writes:
> > 
> > > This reverts commit 498a92d42596a7a32c042319eb62a4c3d8081cf1.
> > >
> > > Krzysztof reported that this change broke Cavium CNS3xxx, ARMv6 (Laguna
> > > GW-2388) because the MRRS setting is never written to the hardware.
> > >
> > > Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > > CC: Arnd Bergmann <arnd@...db.de>
> > > CC: Krzysztof Hałasa <khalasa@...p.pl>
> > > ---
> > >  arch/arm/mach-cns3xxx/pcie.c |   71 ++++++++++++++++++++++++------------------
> > >  1 file changed, 41 insertions(+), 30 deletions(-)
> > 
> > This, applied to v4.7-rc1, fixes the problem on my Laguna boards.
> > 
> > Tested-by: Krzysztof Hałasa <khalasa@...p.pl>
> > 
> > And as well
> > 
> > Acked-by: Krzysztof Hałasa <khalasa@...p.pl>
> 
> Thank!
> 
> Obviously, I'd rather not bring back the gcc warning or the potential
> stack overflow (however unlikely).
> 
> What exactly is the problem we are seeing, and is there a way to fix
> it on top of my patch? Are we perhaps just missing a call to
> pcie_bus_configure_settings()?
> 
> Note that cns3xxx is in a bit of an odd state, as only half of the
> platform code is even present in the kernel, and there is no effort
> to change that. As far as I know, the board that this was tested on
> is not present in the mainline kernel, and the board we support
> is a development system that few people even own at this point.

I'm sure there's a good, simple fix for this that would be better than
the revert.  Unfortunately I don't have time to work on it right now.
I'll be on vacation for the last 2-3 weeks before v4.7 releases, so
I'm scrambling to get the big chunks merged before 6/22 or so.

Bjorn