Re: [PATCH 2/2] PCI: fix system hang issue of Marvell SATA host controller

Bjorn Helgaas
2013-03-08T04:20:05Z

On Thu, Mar 7, 2013 at 8:07 PM, Xiangliang Yu <yuxiangl@marvell.com> wrote:
> Hi, Bjorn
>
>> > Fix system hang issue: if first accessed resource file of BAR0 ~
>> > BAR4, system will hang after executing lspci command
>>
>> This needs more explanation. We've already read the BARs by the time
>> header quirks are run, so apparently it's not just the mere act of
>> accessing a BAR that causes a hang.
>>
>> We need to know exactly what's going on here. For example, do BARs
>> 0-4 exist? Does the device decode accesses to the regions described
>> by the BARs? The PCI core has to know what resources the device uses,
>> so if the device decodes accesses, we can't just throw away the
>> start/end information.
> The BARs 0-4 is exist and the PCI device is enable IO space, but user access the regions file by udevadm command with info parameter, the system will hang.
> Like this: udevadmin info --attribut-walk --path=/sys/device/pci-device/000:*.
> Because the device is just AHCI host controller, don't need the BAR0 ~ 4 region file.
> Is my explanation ok for the patch?

No, I still don't know what causes the hang; I only know that udevadm
can trigger it. I don't want to just paper over the problem until we
know what the root cause is.

Does "lspci -H1 -vv" also cause a hang? What about "setpci -s<dev>
BASE_ADDRESS_0"? "setpci -H1 -s<dev> BASE_ADDRESS_0"?

>>
>> > ---
>> > drivers/pci/quirks.c | 15 +++++++++++++++
>> > 1 files changed, 15 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>> > index 0369fb6..d49f8dc 100644
>> > --- a/drivers/pci/quirks.c
>> > +++ b/drivers/pci/quirks.c
>> > @@ -44,6 +44,21 @@ static void quirk_mmio_always_on(struct pci_dev *dev)
>> > DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_ANY_ID, PCI_ANY_ID,
>> > PCI_CLASS_BRIDGE_HOST, 8,
>> quirk_mmio_always_on);
>> >
>> > +/* The BAR0 ~ BAR4 of Marvell 9125 device can't be accessed
>> > +* by IO resource file, and need to skip the files
>> > +*/
>> > +static void quirk_marvell_mask_bar(struct pci_dev *dev)
>> > +{
>> > + int i;
>> > +
>> > + for (i = 0; i < 5; i++)
>> > + if (dev->resource[i].start)
>> > + dev->resource[i].start =
>> > + dev->resource[i].end = 0;
>> > +}
>> > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_MARVELL_EXT, 0x9125,
>> > + quirk_marvell_mask_bar);
>> > +
>> > /* The Mellanox Tavor device gives false positive parity errors
>> > * Mark this device with a broken_parity_status, to allow
>> > * PCI scanning code to "skip" this now blacklisted device.
>> > --
>> > 1.7.5.4
>> >