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path: root/drivers/acpi/device_pm.c
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Diffstat (limited to 'drivers/acpi/device_pm.c')
-rw-r--r--drivers/acpi/device_pm.c39
1 files changed, 24 insertions, 15 deletions
diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index dd314ef9bff..96de787e610 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -145,27 +145,36 @@ int acpi_device_get_power(struct acpi_device *device, int *state)
}
/*
- * Get the device's power state either directly (via _PSC) or
- * indirectly (via power resources).
+ * Get the device's power state from power resources settings and _PSC,
+ * if available.
*/
+ if (device->power.flags.power_resources) {
+ int error = acpi_power_get_inferred_state(device, &result);
+ if (error)
+ return error;
+ }
if (device->power.flags.explicit_get) {
+ acpi_handle handle = device->handle;
unsigned long long psc;
- acpi_status status = acpi_evaluate_integer(device->handle,
- "_PSC", NULL, &psc);
+ acpi_status status;
+
+ status = acpi_evaluate_integer(handle, "_PSC", NULL, &psc);
if (ACPI_FAILURE(status))
return -ENODEV;
- result = psc;
- }
- /* The test below covers ACPI_STATE_UNKNOWN too. */
- if (result <= ACPI_STATE_D2) {
- ; /* Do nothing. */
- } else if (device->power.flags.power_resources) {
- int error = acpi_power_get_inferred_state(device, &result);
- if (error)
- return error;
- } else if (result == ACPI_STATE_D3_HOT) {
- result = ACPI_STATE_D3;
+ /*
+ * The power resources settings may indicate a power state
+ * shallower than the actual power state of the device.
+ *
+ * Moreover, on systems predating ACPI 4.0, if the device
+ * doesn't depend on any power resources and _PSC returns 3,
+ * that means "power off". We need to maintain compatibility
+ * with those systems.
+ */
+ if (psc > result && psc < ACPI_STATE_D3_COLD)
+ result = psc;
+ else if (result == ACPI_STATE_UNKNOWN)
+ result = psc > ACPI_STATE_D2 ? ACPI_STATE_D3_COLD : psc;
}
/*