Re: [PATCH] PCI/ASPM: Fix a NULL pointer crash on sparc64

[Bjorn Helgaas <bhelgaas@google.com>]

[+cc Dave, Eric, Ben, sparclinux]

On Mon, Aug 17, 2015 at 06:47:58PM +0800, Yijing Wang wrote:
> Commit d0751b98dfa3 ("PCI: Add dev->has_secondary_link to
> track downstream PCIe links")assumed root port is always
> the top device in pcie tree. But on sparc64 V245 and T2000
> the pcie tree has no root port device in top level, the
> upstream port device is connected directly to root bus.
> So we may get NULL parent for this upstream port device.
> 
> Upstream port ------ Downstream port ------PCIe-PCI bridge
> 
> Reported-by: Meelis Roos <mroos@linux.ee>
> Tested-by: Meelis Roos <mroos@linux.ee>
> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
> ---
>  drivers/pci/probe.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 51ebb97..cd54298 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1003,7 +1003,10 @@ void set_pcie_port_type(struct pci_dev *pdev)
>  	else if (type == PCI_EXP_TYPE_UPSTREAM ||
>  		 type == PCI_EXP_TYPE_DOWNSTREAM) {
>  		parent = pci_upstream_bridge(pdev);
> -		if (!parent->has_secondary_link)
> +		/* For sparc64 V245 and T2000, upstream port may be
> +		 * the top level device, connect to root bus directly.
> +		 */
> +		if (parent && !parent->has_secondary_link)
>  			pdev->has_secondary_link = 1;
>  	}
>  }
> -- 
> 1.7.1
>