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>
Index: linux-2.6.22-rc-mm/drivers/acpi/processor_idle.c
===================================================================
--- linux-2.6.22-rc-mm.orig/drivers/acpi/processor_idle.c 2007-06-07 10:47:00.000000000 -0700
+++ linux-2.6.22-rc-mm/drivers/acpi/processor_idle.c 2007-06-07 11:35:07.000000000 -0700
@@ -506,9 +506,9 @@
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 {
/*
@@ -977,8 +977,17 @@
return 0;
}
- /* disable bus master */
- 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.
+ * This the other OS compatible behavior.
+ */
+ if (pr->flags.bm_check && pr->flags.bm_control) {
spin_lock(&c3_lock);
c3_cpu_count++;
if (c3_cpu_count == num_online_cpus()) {
@@ -989,7 +998,7 @@
acpi_set_register(ACPI_BITREG_ARB_DISABLE, 1);
}
spin_unlock(&c3_lock);
- } else {
+ } else if (!pr->flags.bm_check) {
/* SMP with no shared cache... Invalidate cache */
ACPI_FLUSH_CPU_CACHE();
}
@@ -1000,7 +1009,7 @@
acpi_idle_do_entry(cx);
t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
- if (pr->flags.bm_check) {
+ if (pr->flags.bm_check && pr->flags.bm_control) {
spin_lock(&c3_lock);
/* Enable bus master arbitration */
if (c3_cpu_count == num_online_cpus())
-
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