ACPI: Disable ARB_DISABLE on platforms where it is not needed
Pallipadi, Venkatesh [Fri, 22 May 2009 00:09:10 +0000 (17:09 -0700)]
ARB_DISABLE is a NOP on all of the recent Intel platforms.

For such platforms, reduce contention on c3_lock
by skipping the fake ARB_DISABLE.

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

arch/x86/kernel/acpi/cstate.c
drivers/acpi/processor_idle.c

index bbbe4bb..8c44c23 100644 (file)
@@ -34,12 +34,22 @@ void acpi_processor_power_init_bm_check(struct acpi_processor_flags *flags,
                flags->bm_check = 1;
        else if (c->x86_vendor == X86_VENDOR_INTEL) {
                /*
-                * Today all CPUs that support C3 share cache.
-                * TBD: This needs to look at cache shared map, once
-                * multi-core detection patch makes to the base.
+                * Today all MP CPUs that support C3 share cache.
+                * And caches should not be flushed by software while
+                * entering C3 type state.
                 */
                flags->bm_check = 1;
        }
+
+       /*
+        * On all recent Intel platforms, ARB_DISABLE is a nop.
+        * So, set bm_control to zero to indicate that ARB_DISABLE
+        * is not required while entering C3 type state on
+        * P4, Core and beyond CPUs
+        */
+       if (c->x86_vendor == X86_VENDOR_INTEL &&
+           (c->x86 > 0x6 || (c->x86 == 6 && c->x86_model >= 14)))
+                       flags->bm_control = 0;
 }
 EXPORT_SYMBOL(acpi_processor_power_init_bm_check);
 
index 72069ba..4840c79 100644 (file)
@@ -512,7 +512,8 @@ static void acpi_processor_power_verify_c2(struct acpi_processor_cx *cx)
 static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
                                           struct acpi_processor_cx *cx)
 {
-       static int bm_check_flag;
+       static int bm_check_flag = -1;
+       static int bm_control_flag = -1;
 
 
        if (!cx->address)
@@ -542,12 +543,14 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
        }
 
        /* All the logic here assumes flags.bm_check is same across all CPUs */
-       if (!bm_check_flag) {
+       if (bm_check_flag == -1) {
                /* Determine whether bm_check is needed based on CPU  */
                acpi_processor_power_init_bm_check(&(pr->flags), pr->id);
                bm_check_flag = pr->flags.bm_check;
+               bm_control_flag = pr->flags.bm_control;
        } else {
                pr->flags.bm_check = bm_check_flag;
+               pr->flags.bm_control = bm_control_flag;
        }
 
        if (pr->flags.bm_check) {