powerpc: Correct smt_enabled=X boot option for > 2 threads per core

The 'smt_enabled=X' boot option does not handle values of X > 2.
For Power 7 processors with smt modes of 0,1,2,3, and 4 this does
not work.  This patch allows the smt_enabled option to be set to
any value limited to a max equal to the number of threads per
core.

Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 43 insertions, 31 deletions

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 1bee4b68fa45..e72690ec9b87 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -95,7 +95,7 @@ int ucache_bsize;
 
 #ifdef CONFIG_SMP
 
-static int smt_enabled_cmdline;
+static char *smt_enabled_cmdline;
 
 /* Look for ibm,smt-enabled OF option */
 static void check_smt_enabled(void)
@@ -103,37 +103,46 @@ static void check_smt_enabled(void)
         struct device_node *dn;
         const char *smt_option;
 
-        /* Allow the command line to overrule the OF option */
-        if (smt_enabled_cmdline)
-                return;
-
-        dn = of_find_node_by_path("/options");
-
-        if (dn) {
-                smt_option = of_get_property(dn, "ibm,smt-enabled", NULL);
+        /* Default to enabling all threads */
+        smt_enabled_at_boot = threads_per_core;
 
-                if (smt_option) {
-                        if (!strcmp(smt_option, "on"))
-                                smt_enabled_at_boot = 1;
-                        else if (!strcmp(smt_option, "off"))
-                                smt_enabled_at_boot = 0;
-                }
-        }
+        /* Allow the command line to overrule the OF option */
+        if (smt_enabled_cmdline) {
+                if (!strcmp(smt_enabled_cmdline, "on"))
+                        smt_enabled_at_boot = threads_per_core;
+                else if (!strcmp(smt_enabled_cmdline, "off"))
+                        smt_enabled_at_boot = 0;
+                else {
+                        long smt;
+                        int rc;
+
+                        rc = strict_strtol(smt_enabled_cmdline, 10, &smt);
+                        if (!rc)
+                                smt_enabled_at_boot =
+                                        min(threads_per_core, (int)smt);
+                }
+        } else {
+                dn = of_find_node_by_path("/options");
+                if (dn) {
+                        smt_option = of_get_property(dn, "ibm,smt-enabled",
+                                                     NULL);
+
+                        if (smt_option) {
+                                if (!strcmp(smt_option, "on"))
+                                        smt_enabled_at_boot = threads_per_core;
+                                else if (!strcmp(smt_option, "off"))
+                                        smt_enabled_at_boot = 0;
+                        }
+
+                        of_node_put(dn);
+                }
+        }
 }
 
 /* Look for smt-enabled= cmdline option */
 static int __init early_smt_enabled(char *p)
 {
-        smt_enabled_cmdline = 1;
-
-        if (!p)
-                return 0;
-
-        if (!strcmp(p, "on") || !strcmp(p, "1"))
-                smt_enabled_at_boot = 1;
-        else if (!strcmp(p, "off") || !strcmp(p, "0"))
-                smt_enabled_at_boot = 0;
-
+        smt_enabled_cmdline = p;
         return 0;
 }
 early_param("smt-enabled", early_smt_enabled);
@@ -380,8 +389,8 @@ void __init setup_system(void)
          */
         xmon_setup();
 
-        check_smt_enabled();
         smp_setup_cpu_maps();
+        check_smt_enabled();
 
 #ifdef CONFIG_SMP
         /* Release secondary cpus out of their spinloops at 0x60 now that
diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index 3b1bf61c45be..0317cce877c6 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -182,10 +182,13 @@ static int smp_pSeries_cpu_bootable(unsigned int nr)
         /* Special case - we inhibit secondary thread startup
          * during boot if the user requests it.
          */
-        if (system_state < SYSTEM_RUNNING &&
-            cpu_has_feature(CPU_FTR_SMT) &&
-            !smt_enabled_at_boot && cpu_thread_in_core(nr) != 0)
-                return 0;
+        if (system_state < SYSTEM_RUNNING && cpu_has_feature(CPU_FTR_SMT)) {
+                if (!smt_enabled_at_boot && cpu_thread_in_core(nr) != 0)
+                        return 0;
+                if (smt_enabled_at_boot
+                    && cpu_thread_in_core(nr) >= smt_enabled_at_boot)
+                        return 0;
+        }
 
         return 1;
 }