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Commit 8f275615 authored by Jung-uk Kim's avatar Jung-uk Kim Committed by Rafael J. Wysocki
Browse files

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: default avatarJung-uk Kim <jkim@free_BSD.org>
Signed-off-by: default avatarBob Moore <robert.moore@intel.com>
Signed-off-by: default avatarErik Schmauss <erik.schmauss@intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 4fbd8d19

drivers/acpi/acpica/hwtimer.c

+14 −15
Original line number Diff line number Diff line
@@ -153,7 +153,7 @@ acpi_status 
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):
@@ -199,7 +198,7 @@ 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;