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PCI: add ID-based ordering enable/disable support

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Add support to allow drivers to enable/disable ID-based ordering.  Where
supported, ID-based ordering can significantly improve the latency of
individual requests by preventing them from queueing up behind unrelated
traffic.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
This commit is contained in:
Jesse Barnes
2010-10-19 13:07:57 -07:00
parent 69643e4829
commit b48d4425b6
3 changed files with 68 additions and 0 deletions
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53
drivers/pci/pci.c
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@ -1834,6 +1834,59 @@ void pci_enable_ari(struct pci_dev *dev)
bridge->ari_enabled = 1;
}
/**
* pci_enable_ido - enable ID-based ordering on a device
* @dev: the PCI device
* @type: which types of IDO to enable
*
* Enable ID-based ordering on @dev. @type can contain the bits
* %PCI_EXP_IDO_REQUEST and/or %PCI_EXP_IDO_COMPLETION to indicate
* which types of transactions are allowed to be re-ordered.
*/
void pci_enable_ido(struct pci_dev *dev, unsigned long type)
{
int pos;
u16 ctrl;
pos = pci_pcie_cap(dev);
if (!pos)
return;
pci_read_config_word(dev, pos + PCI_EXP_DEVCTL2, &ctrl);
if (type & PCI_EXP_IDO_REQUEST)
ctrl |= PCI_EXP_IDO_REQ_EN;
if (type & PCI_EXP_IDO_COMPLETION)
ctrl |= PCI_EXP_IDO_CMP_EN;
pci_write_config_word(dev, pos + PCI_EXP_DEVCTL2, ctrl);
}
EXPORT_SYMBOL(pci_enable_ido);
/**
* pci_disable_ido - disable ID-based ordering on a device
* @dev: the PCI device
* @type: which types of IDO to disable
*/
void pci_disable_ido(struct pci_dev *dev, unsigned long type)
{
int pos;
u16 ctrl;
if (!pci_is_pcie(dev))
return;
pos = pci_pcie_cap(dev);
if (!pos)
return;
pci_read_config_word(dev, pos + PCI_EXP_DEVCTL2, &ctrl);
if (type & PCI_EXP_IDO_REQUEST)
ctrl &= ~PCI_EXP_IDO_REQ_EN;
if (type & PCI_EXP_IDO_COMPLETION)
ctrl &= ~PCI_EXP_IDO_CMP_EN;
pci_write_config_word(dev, pos + PCI_EXP_DEVCTL2, ctrl);
}
EXPORT_SYMBOL(pci_disable_ido);
static int pci_acs_enable;
/**