ARM: bL_switcher: Add query interface to discover CPU affinities

When the switcher is active, there is no straightforward way to
figure out which logical CPU a given physical CPU maps to.

This patch provides a function
bL_switcher_get_logical_index(mpidr), which is analogous to
get_logical_index().

This function returns the logical CPU on which the specified
physical CPU is grouped (or -EINVAL if unknown).
If the switcher is inactive or not present, -EUNATCH is returned instead.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Nicolas Pitre <nico@linaro.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/arm/common/bL_switcher.c b/arch/arm/common/bL_switcher.c
index 38c852627c3..1883c5b3e3f 100644
--- a/arch/arm/common/bL_switcher.c
+++ b/arch/arm/common/bL_switcher.c
@@ -571,6 +571,26 @@ static int bL_switcher_halve_cpus(void)
 	return 0;
 }
 
+/* Determine the logical CPU a given physical CPU is grouped on. */
+int bL_switcher_get_logical_index(u32 mpidr)
+{
+	int cpu;
+
+	if (!bL_switcher_active)
+		return -EUNATCH;
+
+	mpidr &= MPIDR_HWID_BITMASK;
+	for_each_online_cpu(cpu) {
+		int pairing = bL_switcher_cpu_pairing[cpu];
+		if (pairing == -1)
+			continue;
+		if ((mpidr == cpu_logical_map(cpu)) ||
+		    (mpidr == cpu_logical_map(pairing)))
+			return cpu;
+	}
+	return -EINVAL;
+}
+
 static void bL_switcher_trace_trigger_cpu(void *__always_unused info)
 {
 	trace_cpu_migrate_current(get_ns(), read_mpidr());