[+cc Joao, Niklas, Carlos, Jose, Jesper]
On Fri, Oct 21, 2016 at 10:31:42AM -0500, Bjorn Helgaas wrote:
> On Tue, Oct 18, 2016 at 10:25:49AM +0200, Lucas Stach wrote:
> > The function used to determine if iATU unroll is available will read
> > a RC register. This is not possible and will result in a system hang
> > if the RC is still in reset, so it is only safe to call this function
> > after host_init() has been called.
>
> I'm sure Joao tested a0601a470537 somewhere, so I assume this hang only
> happens on certain systems?
>
> I'm wondering if this is suggesting something that's currently done
> differently across the drivers but could be done more similarly.
>
> > Fixes: a0601a470537 (PCI: designware: Add iATU Unroll feature)
> > Reported-by: Gary Bisson <gary.bisson@xxxxxxxxxxxxxxxxxxx>
> > Tested-by: Gary Bisson <gary.bisson@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> > ---
> > drivers/pci/host/pcie-designware.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pci/host/pcie-designware.c b/drivers/pci/host/pcie-designware.c
> > index 035f50c03281..74510508fafc 100644
> > --- a/drivers/pci/host/pcie-designware.c
> > +++ b/drivers/pci/host/pcie-designware.c
> > @@ -637,11 +637,11 @@ int dw_pcie_host_init(struct pcie_port *pp)
> > }
> > }
> >
> > - pp->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled(pp);
> > -
> > if (pp->ops->host_init)
> > pp->ops->host_init(pp);
> >
> > + pp->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled(pp);
> > +
Niklas suggested this exact change earlier [1], but Joao pointed out the
problem with calling dw_pcie_iatu_unroll_enabled() after calling
pp->ops->host_init():
dw_pcie_host_init
pp->ops->host_init
dw_pcie_setup_rc
dw_pcie_prog_outbound_atu
if (pp->iatu_unroll_enabled)
...
pp->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled()
We check iatu_unroll_enabled in dw_pcie_prog_outbound_atu() before it
has been set.
Niklas' second patch [2] looks like a better fix. Can you guys take a
look and see if you agree?
[1] http://lkml.kernel.org/r/b53d5807-8199-5789-6184-e37324a1d79e@xxxxxxxx
[2] http://lkml.kernel.org/r/1476482095-26289-1-git-send-email-niklass@xxxxxxxx
> > pp->root_bus_nr = pp->busn->start;
> > if (IS_ENABLED(CONFIG_PCI_MSI)) {
> > bus = pci_scan_root_bus_msi(pp->dev, pp->root_bus_nr,
> > --
> > 2.9.3
> >
> > --
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