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>

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 1bee4b6..e72690e 100644 (file)
--- 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 3b1bf61..0317cce 100644 (file)
--- 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;
 }