From: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
On systems that do not have pm2_control_block, we cannot really use
ARB_DISABLE before C3. We used to disable C3 totally on such systems.
To be compatible with Windows, we need to enable C3 on such systems now.
We just skip ARB_DISABLE step before entering the C3-state and assume
hardware is handling things correctly. Also, ACPI spec is not clear
about pm2_control is _needed_ for C3 or not.
We have atleast one system that need this to enable C3.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
---
drivers/acpi/processor_idle.c | 20 +++++++++++++++-----
1 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index ee5759b..36dc1d2 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -488,7 +488,17 @@ static void acpi_processor_idle(void)
case ACPI_STATE_C3:
- if (pr->flags.bm_check) {
+ /*
+ * disable bus master
+ * bm_check implies we need ARB_DIS
+ * !bm_check implies we need cache flush
+ * bm_control implies whether we can do ARB_DIS
+ *
+ * That leaves a case where bm_check is set and bm_control is
+ * not set. In that case we cannot do much, we enter C3
+ * without doing anything.
+ */
+ if (pr->flags.bm_check && pr->flags.bm_control) {
if (atomic_inc_return(&c3_cpu_count) ==
num_online_cpus()) {
/*
@@ -497,7 +507,7 @@ static void acpi_processor_idle(void)
*/
acpi_set_register(ACPI_BITREG_ARB_DISABLE, 1);
}
- } else {
+ } else if (!pr->flags.bm_check) {
/* SMP with no shared cache... Invalidate cache */
ACPI_FLUSH_CPU_CACHE();
}
@@ -509,7 +519,7 @@ static void acpi_processor_idle(void)
acpi_cstate_enter(cx);
/* Get end time (ticks) */
t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
- if (pr->flags.bm_check) {
+ if (pr->flags.bm_check && pr->flags.bm_control) {
/* Enable bus master arbitration */
atomic_dec(&c3_cpu_count);
acpi_set_register(ACPI_BITREG_ARB_DISABLE, 0);
@@ -959,9 +969,9 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
if (pr->flags.bm_check) {
/* bus mastering control is necessary */
if (!pr->flags.bm_control) {
+ /* In this case we enter C3 without bus mastering */
ACPI_DEBUG_PRINT((ACPI_DB_INFO,
- "C3 support requires bus mastering control\n"));
- return;
+ "C3 support without bus mastering control\n"));
}
} else {
/*
--
1.5.3.rc2.22.g69a9b
-
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