MIPS: CPS: Add a couple of multi-cluster utility functions

This patch introduces a couple of utility functions which help later
patches with introducing support for multi-cluster systems.

 - mips_cps_multicluster_cpus() allows its caller to determine whether
   the system includes CPUs spread across multiple clusters. This is
   useful because in some cases behaviour can be more optimal taking
   this knowledge into account. The means by which we check this is
   dependent upon the way we probe CPUs & assign their numbers, so
   keeping this knowledge confined here in arch/mips/ seems appropriate.

 - mips_cps_first_online_in_cluster() allows its caller to determine
   whether it is running upon the first CPU online within its cluster.
   This information is useful in cases where some cluster-wide
   configuration may need to occur, but should not be repeated if
   another CPU in the cluster is already online. Similarly to the above
   this is determined based upon knowledge of CPU numbering so it makes
   sense to keep that knowledge in arch/mips/. The function is defined
   in mips-cm.c rather than in asm/mips-cps.h in order to allow us to
   use asm/cpu-info.h & linux/smp.h without encountering an include
   nightmare.

Signed-off-by: Paul Burton <paulburton@kernel.org>
Signed-off-by: Chao-ying Fu <cfu@wavecomp.com>
Signed-off-by: Dragan Mladjenovic <dragan.mladjenovic@syrmia.com>
Signed-off-by: Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

1 files changed, 37 insertions, 0 deletions

diff --git a/arch/mips/kernel/mips-cm.c b/arch/mips/kernel/mips-cm.c
index 3a115fab5573..3eb2cfb893e1 100644
--- a/arch/mips/kernel/mips-cm.c
+++ b/arch/mips/kernel/mips-cm.c
@@ -512,3 +512,40 @@ void mips_cm_error_report(void)
 	/* reprime cause register */
 	write_gcr_error_cause(cm_error);
 }
+
+unsigned int mips_cps_first_online_in_cluster(void)
+{
+	unsigned int local_cl;
+	int i;
+
+	local_cl = cpu_cluster(&current_cpu_data);
+
+	/*
+	 * We rely upon knowledge that CPUs are numbered sequentially by
+	 * cluster - ie. CPUs 0..X will be in cluster 0, CPUs X+1..Y in cluster
+	 * 1, CPUs Y+1..Z in cluster 2 etc. This means that CPUs in the same
+	 * cluster will immediately precede or follow one another.
+	 *
+	 * First we scan backwards, until we find an online CPU in the cluster
+	 * or we move on to another cluster.
+	 */
+	for (i = smp_processor_id() - 1; i >= 0; i--) {
+		if (cpu_cluster(&cpu_data[i]) != local_cl)
+			break;
+		if (!cpu_online(i))
+			continue;
+		return false;
+	}
+
+	/* Then do the same for higher numbered CPUs */
+	for (i = smp_processor_id() + 1; i < nr_cpu_ids; i++) {
+		if (cpu_cluster(&cpu_data[i]) != local_cl)
+			break;
+		if (!cpu_online(i))
+			continue;
+		return false;
+	}
+
+	/* We found no online CPUs in the local cluster */
+	return true;
+}