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authorMathias Nyman <mathias.nyman@linux.intel.com>2017-06-02 16:36:26 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-08-24 17:15:05 -0700
commite2322bcce28862537c4c31684a3eeaf5a3e27c20 (patch)
parent6632ae821b59916c1a6e38e5a35f80df26faf90c (diff)
usb: optimize acpi companion search for usb port devices
commit ed18c5fa945768a9bec994e786edbbbc7695acf6 upstream. This optimization significantly reduces xhci driver load time. In ACPI tables the acpi companion port devices are children of the hub device. The port devices are identified by their port number returned by the ACPI _ADR method. _ADR 0 is reserved for the root hub device. The current implementation to find a acpi companion port device loops through all acpi port devices under that parent hub, evaluating their _ADR method each time a new port device is added. for a xHC controller with 25 ports under its roothub it will end up invoking ACPI bytecode 625 times before all ports are ready, making it really slow. The _ADR values are already read and cached earler. So instead of running the bytecode again we can check the cached _ADR value first, and then fall back to the old way. As one of the more significant changes, the xhci load time on Intel kabylake reduced by 70%, (28ms) from initcall xhci_pci_init+0x0/0x49 returned 0 after 39537 usecs to initcall xhci_pci_init+0x0/0x49 returned 0 after 11270 usecs Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 23 insertions, 3 deletions
diff --git a/drivers/usb/core/usb-acpi.c b/drivers/usb/core/usb-acpi.c
index 2776cfe64c09..ef9cf4a21afe 100644
--- a/drivers/usb/core/usb-acpi.c
+++ b/drivers/usb/core/usb-acpi.c
@@ -127,6 +127,22 @@ out:
#define USB_ACPI_LOCATION_VALID (1 << 31)
+static struct acpi_device *usb_acpi_find_port(struct acpi_device *parent,
+ int raw)
+ struct acpi_device *adev;
+ if (!parent)
+ return NULL;
+ list_for_each_entry(adev, &parent->children, node) {
+ if (acpi_device_adr(adev) == raw)
+ return adev;
+ }
+ return acpi_find_child_device(parent, raw, false);
static struct acpi_device *usb_acpi_find_companion(struct device *dev)
struct usb_device *udev;
@@ -174,8 +190,10 @@ static struct acpi_device *usb_acpi_find_companion(struct device *dev)
int raw;
raw = usb_hcd_find_raw_port_number(hcd, port1);
- adev = acpi_find_child_device(ACPI_COMPANION(&udev->dev),
- raw, false);
+ adev = usb_acpi_find_port(ACPI_COMPANION(&udev->dev),
+ raw);
if (!adev)
return NULL;
} else {
@@ -186,7 +204,9 @@ static struct acpi_device *usb_acpi_find_companion(struct device *dev)
return NULL;
acpi_bus_get_device(parent_handle, &adev);
- adev = acpi_find_child_device(adev, port1, false);
+ adev = usb_acpi_find_port(adev, port1);
if (!adev)
return NULL;