[POWERPC] Cleanup SMT thread handling

This cleans up the SMT thread handling, removing some hard coded
assumptions and providing a set of helpers to convert between linux
cpu numbers, thread numbers and cores.

This implementation requires the number of threads per core to be a
power of 2 and identical on all cores in the system, but it's an
implementation detail, not an API requirement and so this limitation
can be lifted in the future if anybody ever needs it.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 71 insertions, 0 deletions

diff --git a/include/asm-powerpc/cputhreads.h b/include/asm-powerpc/cputhreads.h
new file mode 100644
index 00000000000..8485c28b5f4
--- /dev/null
+++ b/include/asm-powerpc/cputhreads.h
@@ -0,0 +1,71 @@
+#ifndef _ASM_POWERPC_CPUTHREADS_H
+#define _ASM_POWERPC_CPUTHREADS_H
+
+#include <linux/cpumask.h>
+
+/*
+ * Mapping of threads to cores
+ */
+
+#ifdef CONFIG_SMP
+extern int threads_per_core;
+extern int threads_shift;
+extern cpumask_t threads_core_mask;
+#else
+#define threads_per_core        1
+#define threads_shift           0
+#define threads_core_mask       (CPU_MASK_CPU0)
+#endif
+
+/* cpu_thread_mask_to_cores - Return a cpumask of one per cores
+ *                            hit by the argument
+ *
+ * @threads:    a cpumask of threads
+ *
+ * This function returns a cpumask which will have one "cpu" (or thread)
+ * bit set for each core that has at least one thread set in the argument.
+ *
+ * This can typically be used for things like IPI for tlb invalidations
+ * since those need to be done only once per core/TLB
+ */
+static inline cpumask_t cpu_thread_mask_to_cores(cpumask_t threads)
+{
+        cpumask_t       tmp, res;
+        int             i;
+
+        res = CPU_MASK_NONE;
+        for (i = 0; i < NR_CPUS; i += threads_per_core) {
+                cpus_shift_right(tmp, threads_core_mask, i);
+                if (cpus_intersects(threads, tmp))
+                        cpu_set(i, res);
+        }
+        return res;
+}
+
+static inline int cpu_nr_cores(void)
+{
+        return NR_CPUS >> threads_shift;
+}
+
+static inline cpumask_t cpu_online_cores_map(void)
+{
+        return cpu_thread_mask_to_cores(cpu_online_map);
+}
+
+static inline int cpu_thread_to_core(int cpu)
+{
+        return cpu >> threads_shift;
+}
+
+static inline int cpu_thread_in_core(int cpu)
+{
+        return cpu & (threads_per_core - 1);
+}
+
+static inline int cpu_first_thread_in_core(int cpu)
+{
+        return cpu & ~(threads_per_core - 1);
+}
+
+#endif /* _ASM_POWERPC_CPUTHREADS_H */
+