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SubjectRe: [pci] pci/mrst: Detect loops when reading fixed BAR cap.
Date
On Wednesday, July 14, 2010 11:02:03 am Ben Greear wrote:
> The mrst logic introduced in 2.6.33-rc8 in commit
> a712ffbc199849364c46e9112b93b66de08e2c26 causes boot
> to hang on at least this platform:
>
> Intel E5405 CPU
> System Information
> Manufacturer: Supermicro
> Product Name: X7DBU
>
> The cause of the hang is that pci_cap points to itself
> as the next capability, putting the fixed_bar_cap into
> an endless loop.
>
> This patch detects the loop, prints a warning, and
> continues on with useful work. This strategy was
> suggested by Robert Hancock <hancockrwd@gmail.com>
>
> This should be a candidate for 2.6.34.y as well.
>
> Signed-off-by: Ben Greear <greearb@candelatech.com>
> ---
> :100644 100644 1cdc02c... 9535ba9... M arch/x86/pci/mrst.c
> arch/x86/pci/mrst.c | 11 +++++++++++
> 1 files changed, 11 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/pci/mrst.c b/arch/x86/pci/mrst.c
> index 1cdc02c..9535ba9 100644
> --- a/arch/x86/pci/mrst.c
> +++ b/arch/x86/pci/mrst.c
> @@ -76,6 +76,17 @@ static int fixed_bar_cap(struct pci_bus *bus, unsigned int devfn)
> return pos;
> }
>
> + if ((pcie_cap >> 20) == 0)
> + break;
> +
> + if ((pcie_cap >> 20) <= pos) {
> + printk(KERN_WARNING "WARNING: mrst: detected loop"
> + " when searching for fixed BAR cap, previous"
> + " position: 0x%x new position: 0x%x"
> + " bus-number: %i devfn: %i\n",
> + pos, pcie_cap >> 20, bus->number, devfn);

Can you use dev_warn() here to print the device info in the
standard way?

Bjorn


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