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PCI/ACPI: Optimize device state transition delays

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The PCI "ACPI additions for FW latency optimizations" ECN (link below)
defines two functions in the PCI _DSM:

  Function 8, "Reset Delay," applies to the entire hierarchy below a PCI
  host bridge.  If it returns one, the OS may assume that all devices in
  the hierarchy have already completed power-on reset delays.

  Function 9, "Device Readiness Durations," applies only to the object
  where it is located.  It returns delay durations required after various
  events if the device requires less time than the spec requires.  Delays
  from this function take precedence over the Reset Delay function.

Add support for Reset Delay and part of Device Readiness Durations.

[bhelgaas: changelog, comments]
Link: https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Aaron Lu 2015-03-25 14:37:06 +08:00 • committed by Bjorn Helgaas
commit e33caa82e2
3 changed files with 77 additions and 0 deletions
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2
include/linux/pci-acpi.h
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@ -79,6 +79,8 @@ static inline void acpiphp_check_host_bridge(struct acpi_device *adev) { }
extern const u8 pci_acpi_dsm_uuid[];
#define DEVICE_LABEL_DSM 0x07
#define RESET_DELAY_DSM 0x08
#define FUNCTION_DELAY_DSM 0x09
#else /* CONFIG_ACPI */
static inline void acpi_pci_add_bus(struct pci_bus *bus) { }