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 <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

3 files changed, 36 insertions, 6 deletions

diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c
index 652fd5ce303c..cab13f2fc28e 100644
--- a/drivers/acpi/acpi_lpss.c
+++ b/drivers/acpi/acpi_lpss.c
@@ -164,15 +164,24 @@ static int acpi_lpss_create_device(struct acpi_device *adev,
         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;
         ret = acpi_create_platform_device(adev, id);
         if (ret > 0)
diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index 318fa32a141e..31c217a42839 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -290,6 +290,26 @@ int acpi_bus_init_power(struct acpi_device *device)
         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;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 636c59f2003a..c13c919ab99e 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -382,6 +382,7 @@ const char *acpi_power_state_string(int state);
 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);