cpuidle: fix C3 for no bus-master control case

Port 18eab8550397f1f3d4b8b2c5257c88dae25d58ed
(Enable C3 even when PM2_control is zero) to cpuidle.

Without this patch, some systems will notice a regression
when enabling CPU_IDLE -- C3 would no longer be available.

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

1 files changed, 25 insertions, 10 deletions

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 0cad56ca342b..943a88069001 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -1514,23 +1514,38 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
         } else {
                 acpi_idle_update_bm_rld(pr, cx);
 
-                spin_lock(&c3_lock);
-                c3_cpu_count++;
-                /* Disable bus master arbitration when all CPUs are in C3 */
-                if (c3_cpu_count == num_online_cpus())
-                        acpi_set_register(ACPI_BITREG_ARB_DISABLE, 1);
-                spin_unlock(&c3_lock);
+                /*
+                 * 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) {
+                        spin_lock(&c3_lock);
+                        c3_cpu_count++;
+                        /* Disable bus master arbitration when all CPUs are in C3 */
+                        if (c3_cpu_count == num_online_cpus())
+                                acpi_set_register(ACPI_BITREG_ARB_DISABLE, 1);
+                        spin_unlock(&c3_lock);
+                } else if (!pr->flags.bm_check) {
+                        ACPI_FLUSH_CPU_CACHE();
+                }
 
                 t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
                 acpi_idle_do_entry(cx);
                 t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
 
-                spin_lock(&c3_lock);
                 /* Re-enable bus master arbitration */
-                if (c3_cpu_count == num_online_cpus())
+                if (pr->flags.bm_check && pr->flags.bm_control) {
+                        spin_lock(&c3_lock);
                         acpi_set_register(ACPI_BITREG_ARB_DISABLE, 0);
-                c3_cpu_count--;
-                spin_unlock(&c3_lock);
+                        c3_cpu_count--;
+                        spin_unlock(&c3_lock);
+                }
         }
 
 #if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86_TSC)