linux-kernel - Re: [PATCH] pci: host: xgene: fix incorrectly returned address by map

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Date:	Thu, 5 Mar 2015 10:38:22 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Feng Kan <fkan@....com>
Cc:	patches@....com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, robh@...nel.org,
	linux-arm-kernel@...ts.infradead.org, tinamdar@....com,
	Mark Salter <msalter@...hat.com>
Subject: Re: [PATCH] pci: host: xgene: fix incorrectly returned address by
 map_bus

[+cc Mark]

On Thu, Feb 26, 2015 at 06:21:51PM -0600, Bjorn Helgaas wrote:
> On Tue, Feb 17, 2015 at 03:14:00PM -0800, Feng Kan wrote:
> > The generic accessor functions for pci-xgene uses map_bus
> > call that returns the base address but did not add the additional
> > offset.
> > 
> > Signed-off-by: Feng Kan <fkan@....com>
> > ---
> >  drivers/pci/host/pci-xgene.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/host/pci-xgene.c b/drivers/pci/host/pci-xgene.c
> > index aab5547..ee082c0 100644
> > --- a/drivers/pci/host/pci-xgene.c
> > +++ b/drivers/pci/host/pci-xgene.c
> > @@ -127,7 +127,7 @@ static bool xgene_pcie_hide_rc_bars(struct pci_bus *bus, int offset)
> >  	return false;
> >  }
> >  
> > -static int xgene_pcie_map_bus(struct pci_bus *bus, unsigned int devfn,
> > +static void __iomem *xgene_pcie_map_bus(struct pci_bus *bus, unsigned int devfn,
> >  			      int offset)
> >  {
> >  	struct xgene_pcie_port *port = bus->sysdata;
> > @@ -137,7 +137,7 @@ static int xgene_pcie_map_bus(struct pci_bus *bus, unsigned int devfn,
> >  		return NULL;
> >  
> >  	xgene_pcie_set_rtdid_reg(bus, devfn);
> > -	return xgene_pcie_get_cfg_base(bus);
> > +	return xgene_pcie_get_cfg_base(bus) + offset;
> 
> Where's the locking here?  ECAM doesn't need locking because the
> bus/dev/fn/offset is all encoded in the MMIO address.  But it looks
> like X-Gene doesn't work that way and bus/dev/fn is in the RTDID register.
> 
> So it seems like X-Gene needs locking that not everybody needs.  Are you
> relying on higher-level locking somewhere?

Ping, what's going on here?  I've gotten at least three patches for this
offset issue, so we need to get it resolved.

If there's no locking problem, I can just apply this and we'll be finished.
Actually, I think Mark's patch is better, because it correctly returns NULL
(failure) if xgene_pcie_get_cfg_base() fails.  So please review and ack
that one or explain why this one is better.

But if there *is* a locking problem, we should fix that, too.  That should
be a separate patch, so I guess I can apply the one to fix the offset
problem first, and we'll at least be no worse off with respect to locking
than we are today.

Please help me out.

Bjorn

> >  }
> >  
> >  static struct pci_ops xgene_pcie_ops = {
> > -- 
> > 1.9.1
> > 
> > --
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