[PATCH 26/98] ACPICA: Do not use extended sleep registers unless HW-reduced bit is set

[Luis Henriques]

3.5.7.17 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lv Zheng <lv.zheng@xxxxxxxxx>

commit 7cec7048fe22e3e92389da2cd67098f6c4284e7f upstream.

Previous implementation incorrectly used the ACPI 5.0 extended
sleep registers if they were simply populated. This caused
problems on some non-HW-reduced machines. As per the ACPI spec,
they should only be used if the HW-reduced bit is set.  Lv Zheng,
ACPICA BZ 1020.

References: https://bugzilla.kernel.org/show_bug.cgi?id=54181
References: https://bugs.acpica.org/show_bug.cgi?id=1020
Reported-by: Daniel Rowe <bart@xxxxxxxxxxxx>
Bisected-by: Brint E. Kriebel <kernel@xxxxxxxxx>
Signed-off-by: Lv Zheng <lv.zheng@xxxxxxxxx>
Signed-off-by: Bob Moore <robert.moore@xxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 drivers/acpi/acpica/hwxfsleep.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/acpica/hwxfsleep.c b/drivers/acpi/acpica/hwxfsleep.c
index 762d059..a8af0ba 100644
--- a/drivers/acpi/acpica/hwxfsleep.c
+++ b/drivers/acpi/acpica/hwxfsleep.c
@@ -242,12 +242,14 @@ acpi_hw_sleep_dispatch(u8 sleep_state, u8 flags, u32 function_id)
 	    &acpi_sleep_dispatch[function_id];
 
 #if (!ACPI_REDUCED_HARDWARE)
-
 	/*
 	 * If the Hardware Reduced flag is set (from the FADT), we must
-	 * use the extended sleep registers
+	 * use the extended sleep registers (FADT). Note: As per the ACPI
+	 * specification, these extended registers are to be used for HW-reduced
+	 * platforms only. They are not general-purpose replacements for the
+	 * legacy PM register sleep support.
 	 */
-	if (acpi_gbl_reduced_hardware || acpi_gbl_FADT.sleep_control.address) {
+	if (acpi_gbl_reduced_hardware) {
 		status = sleep_functions->extended_function(sleep_state, flags);
 	} else {
 		/* Legacy sleep */
-- 
1.8.1.2

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