[Skiboot] [PATCH v1] external/mambo: Add POWER10 small-core mode

[Nicholas Piggin]

If the SMT configuration is not 8, set small-core mode in SIM_CTRL1
and PVR registers.

Also allow only 1, 2, 4, or 8 threads, and only allow 1 and 2 threads
if there is only one processor configured. This helps avoid strange
crashes due to thread/core enumeration problems with unexpected threads
per core.

Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
 external/mambo/skiboot.tcl | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/external/mambo/skiboot.tcl b/external/mambo/skiboot.tcl
index 68bedbcfc..fb6c93547 100644
--- a/external/mambo/skiboot.tcl
+++ b/external/mambo/skiboot.tcl
@@ -147,11 +147,28 @@ if { $default_config == "P9" } {
 }
 
 if { $default_config == "P10" } {
-    # PVR configured for POWER10 DD2.0, big-core, LPAR-per-thread
-    # Small-core has bit 0x1000 set.
-    myconf config processor/initial/PVR 0x800200
+    # PVR configured for POWER10 DD2.0, LPAR-per-thread
     myconf config processor/initial/SIM_CTRL  0x0c1dd60000000000
-    myconf config processor/initial/SIM_CTRL1 0xc0400c0400040a40
+    if { $mconf(threads) == 8 } {
+        # Big-core mode.
+        myconf config processor/initial/PVR 0x00800200
+        myconf config processor/initial/SIM_CTRL1 0xc0400c0400040a40
+	puts "Set P10 big-core mode"
+    } else {
+        # Small-core mode.
+        myconf config processor/initial/PVR 0x00801200
+        myconf config processor/initial/SIM_CTRL1 0xc0400c0401040a40
+        if { $mconf(threads) != 1 && $mconf(threads) != 2 && $mconf(threads) != 4 } {
+            puts "ERROR: Bad threads configuration"
+            exit
+        }
+        if { $mconf(threads) != 4 && $mconf(cpus) != 1 } {
+            puts "ERROR: Bad threads, cpus configuration"
+            exit
+        }
+
+	puts "Set P10 small-core mode"
+    }
 
     if { $mconf(numa) } {
         myconf config memory_region_id_shift 44
-- 
2.23.0