Re: [PATCH resend] PCI: designware: fix register access before host init

[Bjorn Helgaas <helgaas@kernel.org>]

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@boundarydevices.com>
> Tested-by: Gary Bisson <gary.bisson@boundarydevices.com>
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  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);
> +
>  	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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