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authorAaron Lu <aaron.lu@intel.com>2015-03-25 14:37:06 +0800
committerBjorn Helgaas <bhelgaas@google.com>2015-04-08 16:25:25 -0500
commite33caa82e221b0bbeba373b507e3f134dc2efa1a (patch)
tree5a5b5cb497a21c0342ac0a7d2956b366020fef68 /drivers/pci
parent3390e0850b711d163b35508464cfbe0a4477dfe2 (diff)
downloadlinux-e33caa82e221b0bbeba373b507e3f134dc2efa1a.tar.bz2
PCI/ACPI: Optimize device state transition delays
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>
Diffstat (limited to 'drivers/pci')
-rw-r--r--drivers/pci/pci-acpi.c74
1 files changed, 74 insertions, 0 deletions
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index bea6be4992c3..5eba74716900 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -537,11 +537,32 @@ static struct pci_platform_pm_ops acpi_pci_platform_pm = {
void acpi_pci_add_bus(struct pci_bus *bus)
{
+ union acpi_object *obj;
+ struct pci_host_bridge *bridge;
+
if (acpi_pci_disabled || !bus->bridge)
return;
acpi_pci_slot_enumerate(bus);
acpiphp_enumerate_slots(bus);
+
+ /*
+ * For a host bridge, check its _DSM for function 8 and if
+ * that is available, mark it in pci_host_bridge.
+ */
+ if (!pci_is_root_bus(bus))
+ return;
+
+ obj = acpi_evaluate_dsm(ACPI_HANDLE(bus->bridge), pci_acpi_dsm_uuid, 3,
+ RESET_DELAY_DSM, NULL);
+ if (!obj)
+ return;
+
+ if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1) {
+ bridge = pci_find_host_bridge(bus);
+ bridge->ignore_reset_delay = 1;
+ }
+ ACPI_FREE(obj);
}
void acpi_pci_remove_bus(struct pci_bus *bus)
@@ -567,6 +588,57 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
check_children);
}
+/**
+ * pci_acpi_optimize_delay - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either the device itself or the PCI host bridge.
+ *
+ * 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.
+ *
+ * These _DSM functions are defined by the draft ECN of January 28, 2014,
+ * titled "ACPI additions for FW latency optimizations."
+ */
+static void pci_acpi_optimize_delay(struct pci_dev *pdev,
+ acpi_handle handle)
+{
+ struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus);
+ int value;
+ union acpi_object *obj, *elements;
+
+ if (bridge->ignore_reset_delay)
+ pdev->d3cold_delay = 0;
+
+ obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 3,
+ FUNCTION_DELAY_DSM, NULL);
+ if (!obj)
+ return;
+
+ if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+ elements = obj->package.elements;
+ if (elements[0].type == ACPI_TYPE_INTEGER) {
+ value = (int)elements[0].integer.value / 1000;
+ if (value < PCI_PM_D3COLD_WAIT)
+ pdev->d3cold_delay = value;
+ }
+ if (elements[3].type == ACPI_TYPE_INTEGER) {
+ value = (int)elements[3].integer.value / 1000;
+ if (value < PCI_PM_D3_WAIT)
+ pdev->d3_delay = value;
+ }
+ }
+ ACPI_FREE(obj);
+}
+
static void pci_acpi_setup(struct device *dev)
{
struct pci_dev *pci_dev = to_pci_dev(dev);
@@ -575,6 +647,8 @@ static void pci_acpi_setup(struct device *dev)
if (!adev)
return;
+ pci_acpi_optimize_delay(pci_dev, adev->handle);
+
pci_acpi_add_pm_notifier(adev, pci_dev);
if (!adev->wakeup.flags.valid)
return;