ACPICA: Fix an off-by-one error in acpi_get_timer_duration().

ACPICA commit b4fd33f3c2af014aeec978d46392d286fd7f52b3

Delta calculation has an off-by-one error when there is a rollover.
For example, when start_ticks is 0x00FFFFFF and end_ticks is 0x00000000
(for 24-bit timer), delta_ticks should be 1 (one) but it was 0 (zero).

Link: https://github.com/acpica/acpica/commit/b4fd33f3
Signed-off-by: Jung-uk Kim <jkim@free_BSD.org>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Erik Schmauss <erik.schmauss@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/acpica/hwtimer.c b/drivers/acpi/acpica/hwtimer.c
index a2f4e25..5b42829 100644 (file)
--- a/drivers/acpi/acpica/hwtimer.c
+++ b/drivers/acpi/acpica/hwtimer.c
@@ -150,10 +150,10 @@ ACPI_EXPORT_SYMBOL(acpi_get_timer)
  *
  ******************************************************************************/
 acpi_status
-acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
+acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 *time_elapsed)
 {
        acpi_status status;
-       u32 delta_ticks;
+       u64 delta_ticks;
        u64 quotient;
 
        ACPI_FUNCTION_TRACE(acpi_get_timer_duration);
@@ -168,30 +168,29 @@ acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
                return_ACPI_STATUS(AE_SUPPORT);
        }
 
+       if (start_ticks == end_ticks) {
+               *time_elapsed = 0;
+               return_ACPI_STATUS(AE_OK);
+       }
+
        /*
         * Compute Tick Delta:
         * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
         */
-       if (start_ticks < end_ticks) {
-               delta_ticks = end_ticks - start_ticks;
-       } else if (start_ticks > end_ticks) {
+       delta_ticks = end_ticks;
+       if (start_ticks > end_ticks) {
                if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
 
                        /* 24-bit Timer */
 
-                       delta_ticks =
-                           (((0x00FFFFFF - start_ticks) +
-                             end_ticks) & 0x00FFFFFF);
+                       delta_ticks |= (u64)1 << 24;
                } else {
                        /* 32-bit Timer */
 
-                       delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
+                       delta_ticks |= (u64)1 << 32;
                }
-       } else {                /* start_ticks == end_ticks */
-
-               *time_elapsed = 0;
-               return_ACPI_STATUS(AE_OK);
        }
+       delta_ticks -= start_ticks;
 
        /*
         * Compute Duration (Requires a 64-bit multiply and divide):
@@ -199,10 +198,10 @@ acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
         * time_elapsed (microseconds) =
         *  (delta_ticks * ACPI_USEC_PER_SEC) / ACPI_PM_TIMER_FREQUENCY;
         */
-       status = acpi_ut_short_divide(((u64)delta_ticks) * ACPI_USEC_PER_SEC,
+       status = acpi_ut_short_divide(delta_ticks * ACPI_USEC_PER_SEC,
                                      ACPI_PM_TIMER_FREQUENCY, &quotient, NULL);
 
-       *time_elapsed = (u32) quotient;
+       *time_elapsed = (u32)quotient;
        return_ACPI_STATUS(status);
 }