ACPICA: Limit maximum time for Sleep() operator

To prevent accidental deep sleeps, limit the maximum time that
Sleep() will sleep. Configurable, default maximum is two seconds.
ACPICA bugzilla 854.

http://www.acpica.org/bugzilla/show_bug.cgi?id=854

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/acpica/acconfig.h

@@ -119,6 +119,10 @@
 
 #define ACPI_MAX_LOOP_ITERATIONS        0xFFFF
 
+/* Maximum sleep allowed via Sleep() operator */
+
+#define ACPI_MAX_SLEEP                  20000	/* Two seconds */
+
 /******************************************************************************
  *
  * ACPI Specification constants (Do not change unless the specification changes)

drivers/acpi/acpica/exsystem.c

@@ -201,6 +201,14 @@ acpi_status acpi_ex_system_do_sleep(u64 how_long)
 
 	acpi_ex_relinquish_interpreter();
 
+	/*
+	 * For compatibility with other ACPI implementations and to prevent
+	 * accidental deep sleeps, limit the sleep time to something reasonable.
+	 */
+	if (how_long > ACPI_MAX_SLEEP) {
+		how_long = ACPI_MAX_SLEEP;
+	}
+
 	acpi_os_sleep(how_long);
 
 	/* And now we must get the interpreter again */