Xen devel - Dec 2008 - [PATCH] Enable C3 without bm control only for CST based C3

domain0 patch: pull from Linux kernel upstream, to get correct C3 info in
certain newer machine.

commit ed3110efb538d7acbf635095c1382118f7414f75
Author: Venki Pallipadi <venkatesh.pallipadi@intel.com>
Date:   Tue Jul 31 12:04:31 2007 -0700

    ACPI: fix "Time Problems with 2.6.23-rc1-gf695baf2"

    Enable C3 without bm control only for CST based C3.

    Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
    Signed-off-by: Len Brown <len.brown@intel.com>

diff -r a070228ac76e -r 5e8ad099d5c8 drivers/acpi/processor_idle.c
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -857,11 +857,17 @@ static void acpi_processor_power_verify_
 	}
 
 	if (pr->flags.bm_check) {
-		/* bus mastering control is necessary */
 		if (!pr->flags.bm_control) {
-			ACPI_DEBUG_PRINT((ACPI_DB_INFO,
-					  "C3 support requires bus mastering control\n"));
-			return;
+			if (pr->flags.has_cst != 1) {
+				/* bus mastering control is necessary */
+				ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+					"C3 support requires BM control\n"));
+				return;
+			} else {
+				/* Here we enter C3 without bus mastering */
+				ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+					"C3 support without BM control\n"));
+			}
 		}
 	} else {
 		/*

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