diff --git a/drivers/acpi/acpica/hwtimer.c b/drivers/acpi/acpica/hwtimer.c
index 0c1a8bbd05d6..2d7d22ebc782 100644
--- a/drivers/acpi/acpica/hwtimer.c
+++ b/drivers/acpi/acpica/hwtimer.c
@@ -100,8 +100,13 @@ acpi_status acpi_get_timer(u32 * ticks)
 		return_ACPI_STATUS(AE_BAD_PARAMETER);
 	}
 
-	status = acpi_hw_read(ticks, &acpi_gbl_FADT.xpm_timer_block);
+	/* ACPI 5.0A: PM Timer is optional */
 
+	if (!acpi_gbl_FADT.xpm_timer_block.address) {
+		return_ACPI_STATUS(AE_SUPPORT);
+	}
+
+	status = acpi_hw_read(ticks, &acpi_gbl_FADT.xpm_timer_block);
 	return_ACPI_STATUS(status);
 }
 
@@ -148,6 +153,12 @@ acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
 		return_ACPI_STATUS(AE_BAD_PARAMETER);
 	}
 
+	/* ACPI 5.0A: PM Timer is optional */
+
+	if (!acpi_gbl_FADT.xpm_timer_block.address) {
+		return_ACPI_STATUS(AE_SUPPORT);
+	}
+
 	/*
 	 * Compute Tick Delta:
 	 * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
diff --git a/drivers/acpi/acpica/tbfadt.c b/drivers/acpi/acpica/tbfadt.c
index 33b00d22300a..9d99f2189693 100644
--- a/drivers/acpi/acpica/tbfadt.c
+++ b/drivers/acpi/acpica/tbfadt.c
@@ -117,7 +117,7 @@ static struct acpi_fadt_info fadt_info_table[] = {
 	 ACPI_FADT_OFFSET(pm_timer_block),
 	 ACPI_FADT_OFFSET(pm_timer_length),
 	 ACPI_PM_TIMER_WIDTH,
-	 ACPI_FADT_REQUIRED},
+	 ACPI_FADT_SEPARATE_LENGTH},	/* ACPI 5.0A: Timer is optional */
 
 	{"Gpe0Block",
 	 ACPI_FADT_OFFSET(xgpe0_block),
@@ -574,7 +574,7 @@ static void acpi_tb_validate_fadt(void)
 
 		if (fadt_info_table[i].type & ACPI_FADT_REQUIRED) {
 			/*
-			 * Field is required (Pm1a_event, Pm1a_control, pm_timer).
+			 * Field is required (Pm1a_event, Pm1a_control).
 			 * Both the address and length must be non-zero.
 			 */
 			if (!address64->address || !length) {