[ACPI] Avoid BIOS inflicted crashes by evaluating _PDC only once

Linux invokes the AML _PDC method (Processor Driver Capabilities)
to tell the BIOS what features it can handle.  While the ACPI
spec says nothing about the OS invoking _PDC multiple times,
doing so with changing bits seems to hopelessly confuse the BIOS
on multiple platforms up to and including crashing the system.

Factor out the _PDC invocation so Linux invokes it only once.

http://bugzilla.kernel.org/show_bug.cgi?id=5483

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

1 files changed, 11 insertions, 17 deletions

diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index 421792562642..66bbda78507a 100644
--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -253,31 +253,21 @@ static int acpi_processor_errata(struct acpi_processor *pr)
  * _PDC is required for a BIOS-OS handshake for most of the newer
  * ACPI processor features.
  */
-
-int acpi_processor_set_pdc(struct acpi_processor *pr,
-                           struct acpi_object_list *pdc_in)
+static int acpi_processor_set_pdc(struct acpi_processor *pr)
 {
+        struct acpi_object_list *pdc_in = pr->pdc;
         acpi_status status = AE_OK;
-        u32 arg0_buf[3];
-        union acpi_object arg0 = { ACPI_TYPE_BUFFER };
-        struct acpi_object_list no_object = { 1, &arg0 };
-        struct acpi_object_list *pdc;
 
         ACPI_FUNCTION_TRACE("acpi_processor_set_pdc");
 
-        arg0.buffer.length = 12;
-        arg0.buffer.pointer = (u8 *) arg0_buf;
-        arg0_buf[0] = ACPI_PDC_REVISION_ID;
-        arg0_buf[1] = 0;
-        arg0_buf[2] = 0;
-
-        pdc = (pdc_in) ? pdc_in : &no_object;
+        if (!pdc_in)
+                return_VALUE(status);
 
-        status = acpi_evaluate_object(pr->handle, "_PDC", pdc, NULL);
+        status = acpi_evaluate_object(pr->handle, "_PDC", pdc_in, NULL);
 
-        if ((ACPI_FAILURE(status)) && (pdc_in))
+        if (ACPI_FAILURE(status))
                 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
-                                  "Error evaluating _PDC, using legacy perf. control...\n"));
+                    "Could not evaluate _PDC, using legacy perf. control...\n"));
 
         return_VALUE(status);
 }
@@ -574,6 +564,10 @@ static int acpi_processor_start(struct acpi_device *device)
                                   "Error installing device notify handler\n"));
         }
 
+        /* _PDC call should be done before doing anything else (if reqd.). */
+        arch_acpi_processor_init_pdc(pr);
+        acpi_processor_set_pdc(pr);
+
         acpi_processor_power_init(pr, device);
 
         if (pr->flags.throttling) {