ACPI: scan: Avoid unnecessary second pass in acpi_bus_scan()

If there are no devices whose enumeration has been deferred after
the first pass in acpi_bus_scan(), the second pass is not necssary,
so avoid it with the help of a new static variable.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 00f1b09..2871374 100644 (file)
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1910,6 +1910,8 @@ static void acpi_scan_dep_init(struct acpi_device *adev)
        mutex_unlock(&acpi_dep_list_lock);
 }
 
+static bool acpi_bus_scan_second_pass;
+
 static acpi_status acpi_bus_check_add(acpi_handle handle, bool check_dep,
                                      struct acpi_device **adev_p)
 {
@@ -1934,8 +1936,10 @@ static acpi_status acpi_bus_check_add(acpi_handle handle, bool check_dep,
        if (type == ACPI_BUS_TYPE_DEVICE && check_dep) {
                u32 count = acpi_scan_check_dep(handle);
                /* Bail out if the number of recorded dependencies is not 0. */
-               if (count > 0)
+               if (count > 0) {
+                       acpi_bus_scan_second_pass = true;
                        return AE_CTRL_DEPTH;
+               }
        }
 
        acpi_add_single_object(&device, handle, type, sta);
@@ -2136,6 +2140,8 @@ int acpi_bus_scan(acpi_handle handle)
 {
        struct acpi_device *device = NULL;
 
+       acpi_bus_scan_second_pass = false;
+
        /* Pass 1: Avoid enumerating devices with missing dependencies. */
 
        if (ACPI_SUCCESS(acpi_bus_check_add(handle, true, &device)))
@@ -2148,6 +2154,9 @@ int acpi_bus_scan(acpi_handle handle)
 
        acpi_bus_attach(device, true);
 
+       if (!acpi_bus_scan_second_pass)
+               return 0;
+
        /* Pass 2: Enumerate all of the remaining devices. */
 
        device = NULL;