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    Subject[RFC] disable PCIE 'Enable No Snoop' bit by default
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    PCIE 'Enable No Snoop' bit is set by default per PCIE spec, but OS
    assumes PCI DMA is snooped, which is legacy PCI device does. Enabling no
    snoop might cause potential DMA issues. This patch disables it, if a
    driver can work with no snoop, we can provide a helper to enable it.

    I didn't see any real breaks, but did see some devices with the bit enabled

    Signed-off-by: Shaohua Li <shaohua.li@intel.com>

    Index: linux/drivers/pci/probe.c
    ===================================================================
    --- linux.orig/drivers/pci/probe.c 2007-09-06 13:18:07.000000000 +0800
    +++ linux/drivers/pci/probe.c 2007-09-06 13:21:30.000000000 +0800
    @@ -694,6 +694,19 @@ static void pci_read_irq(struct pci_dev

    #define LEGACY_IO_RESOURCE (IORESOURCE_IO | IORESOURCE_PCI_FIXED)

    +static void pcie_setup_device(struct pci_dev *dev)
    +{
    + u16 reg16;
    + int pos;
    +
    + pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
    + if (pos) {
    + pci_read_config_word(dev, pos + PCI_EXP_DEVCTL, &reg16);
    + reg16 &= ~PCI_EXP_DEVCTL_NOSNOOP_EN;
    + pci_write_config_word(dev, pos + PCI_EXP_DEVCTL, reg16);
    + }
    +}
    +
    /**
    * pci_setup_device - fill in class and map information of a device
    * @dev: the device structure to fill
    @@ -795,6 +808,7 @@ static int pci_setup_device(struct pci_d
    dev->class = PCI_CLASS_NOT_DEFINED;
    }

    + pcie_setup_device(dev);
    /* We found a fine healthy device, go go go... */
    return 0;
    }
    -
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