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SubjectRe: [PATCH] pci: host: xgene: fix incorrectly returned address by map_bus
On Thu, Mar 5, 2015 at 10:38 AM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> [+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@apm.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.

There's no locking problem. The config accesses are all within the
pci_lock spinlock and nothing else touches that register.

Rob


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