ACPI / LPSS: Power up LPSS devices during enumeration

Commit 7cd8407 (ACPI / PM: Do not execute _PS0 for devices without
_PSC during initialization) introduced a regression on some systems
with Intel Lynxpoint Low-Power Subsystem (LPSS) where some devices
need to be powered up during initialization, but their device objects
in the ACPI namespace have _PS0 and _PS3 only (without _PSC or power
resources).

To work around this problem, make the ACPI LPSS driver power up
devices it knows about by using a new helper function
acpi_device_fix_up_power() that does all of the necessary
sanity checks and calls acpi_dev_pm_explicit_set() to put the
device into D0.

Reported-and-tested-by: Mika Westerberg <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/acpi_lpss.c

···
 	if (dev_desc->clk_required) {
 		ret = register_device_clock(adev, pdata);
 		if (ret) {
-			/*
-			 * Skip the device, but don't terminate the namespace
-			 * scan.
-			 */
-			kfree(pdata);
-			return 0;
+			/* Skip the device, but continue the namespace scan. */
+			ret = 0;
+			goto err_out;
 		}
+	}
+
+	/*
+	 * This works around a known issue in ACPI tables where LPSS devices
+	 * have _PS0 and _PS3 without _PSC (and no power resources), so
+	 * acpi_bus_init_power() will assume that the BIOS has put them into D0.
+	 */
+	ret = acpi_device_fix_up_power(adev);
+	if (ret) {
+		/* Skip the device, but continue the namespace scan. */
+		ret = 0;
+		goto err_out;
 	}
 
 	adev->driver_data = pdata;

drivers/acpi/device_pm.c

···
 	return 0;
 }
 
+/**
+ * acpi_device_fix_up_power - Force device with missing _PSC into D0.
+ * @device: Device object whose power state is to be fixed up.
+ *
+ * Devices without power resources and _PSC, but having _PS0 and _PS3 defined,
+ * are assumed to be put into D0 by the BIOS.  However, in some cases that may
+ * not be the case and this function should be used then.
+ */
+int acpi_device_fix_up_power(struct acpi_device *device)
+{
+	int ret = 0;
+
+	if (!device->power.flags.power_resources
+	    && !device->power.flags.explicit_get
+	    && device->power.state == ACPI_STATE_D0)
+		ret = acpi_dev_pm_explicit_set(device, ACPI_STATE_D0);
+
+	return ret;
+}
+
 int acpi_bus_update_power(acpi_handle handle, int *state_p)
 {
 	struct acpi_device *device;

include/acpi/acpi_bus.h

···
 int acpi_device_get_power(struct acpi_device *device, int *state);
 int acpi_device_set_power(struct acpi_device *device, int state);
 int acpi_bus_init_power(struct acpi_device *device);
+int acpi_device_fix_up_power(struct acpi_device *device);
 int acpi_bus_update_power(acpi_handle handle, int *state_p);
 bool acpi_bus_power_manageable(acpi_handle handle);