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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
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

53
drivers/pci/pci.c
View file

@ -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;
/**

13
include/linux/pci.h
View file

@ -828,6 +828,11 @@ static inline int pci_enable_wake(struct pci_dev *dev, pci_power_t state,
return __pci_enable_wake(dev, state, false, enable);
}
#define PCI_EXP_IDO_REQUEST (1<<0)
#define PCI_EXP_IDO_COMPLETION (1<<1)
void pci_enable_ido(struct pci_dev *dev, unsigned long type);
void pci_disable_ido(struct pci_dev *dev, unsigned long type);
/* For use by arch with custom probe code */
void set_pcie_port_type(struct pci_dev *pdev);
void set_pcie_hotplug_bridge(struct pci_dev *pdev);
@ -1207,6 +1212,14 @@ static inline int pci_enable_wake(struct pci_dev *dev, pci_power_t state,
return 0;
}
static inline void pci_enable_ido(struct pci_dev *dev, unsigned long type)
{
}
static inline void pci_disable_ido(struct pci_dev *dev, unsigned long type)
{
}
static inline int pci_request_regions(struct pci_dev *dev, const char *res_name)
{
return -EIO;

2
include/linux/pci_regs.h
View file

@ -510,6 +510,8 @@
#define PCI_EXP_DEVCAP2_ARI 0x20 /* Alternative Routing-ID */
#define PCI_EXP_DEVCTL2 40 /* Device Control 2 */
#define PCI_EXP_DEVCTL2_ARI 0x20 /* Alternative Routing-ID */
#define PCI_EXP_IDO_REQ_EN 0x100 /* ID-based ordering request enable */
#define PCI_EXP_IDO_CMP_EN 0x200 /* ID-based ordering completion enable */
#define PCI_EXP_LNKCTL2 48 /* Link Control 2 */
#define PCI_EXP_SLTCTL2 56 /* Slot Control 2 */