ACPICA: Make ACPI Power Management Timer (PM Timer) optional.

PM Timer is now optional.
This support is already in Windows8 and "SHOULD" come out in ACPI 5.0A
(if all goes well).

The change doesn't affect Linux directly, because it does not rely
on the presence of the PM timer.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 14 insertions, 3 deletions

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) {