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@xxxxxxxxxxxxxxxx> --- drivers/pci/pci.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++ include/linux/pci.h | 13 +++++++++++ include/linux/pci_regs.h | 2 + 3 files changed, 69 insertions(+), 0 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 44d1c7c..44bf8f0 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1834,6 +1834,60 @@ 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; + + 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); +} + +/** + * 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); +} + static int pci_acs_enable; /** diff --git a/include/linux/pci.h b/include/linux/pci.h index 96f70d7..551ddcb 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -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; diff --git a/include/linux/pci_regs.h b/include/linux/pci_regs.h index be01380..d9acf9b 100644 --- a/include/linux/pci_regs.h +++ b/include/linux/pci_regs.h @@ -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 */ -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html