POWERSAVE_LB: If all cpus are non-idle, then fallback

    to normal TT balancing. Since no energy
    saving at this point, at least try to
    use cpu affain.

patches/5.15/tt-5.15.patch

@@ -140,10 +140,10 @@ index 978fcfca5871..bfde8e0d851b 100644
  obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o stop_task.o pelt.o
 diff --git a/kernel/sched/bs.c b/kernel/sched/bs.c
 new file mode 100644
-index 000000000000..ad79be3d4c45
+index 000000000000..8c1097870394
 --- /dev/null
 +++ b/kernel/sched/bs.c
-@@ -0,0 +1,1876 @@
+@@ -0,0 +1,1888 @@
 +// SPDX-License-Identifier: GPL-2.0
 +/*
 + * TT Scheduler Class (SCHED_NORMAL/SCHED_BATCH)
@@ -1186,6 +1186,7 @@ index 000000000000..ad79be3d4c45
 +	int target = -1, cpu;
 +	struct tt_node *ttn = &p->se.tt_node;
 +	unsigned int min = ~0;
++	bool all_non_idle = true;
 +
 +	/*
 +	 * If type is realtime, interactive, or no type,
@@ -1198,15 +1199,26 @@ index 000000000000..ad79be3d4c45
 +		if (unlikely(!cpumask_test_cpu(cpu, p->cpus_ptr)))
 +			continue;
 +
-+		if (idle_cpu(cpu))
++		if (idle_cpu(cpu)) {
++			all_non_idle = false;
 +			continue;
++		}
 +
 +		if (cpu_rq(cpu)->nr_running < min) {
 +			target = cpu;
 +			min = cpu_rq(cpu)->nr_running;
 +		}
 +	}
 +
++	/*
++	 * If all cpus are non-idle, then fallback
++	 * to normal TT balancing. Since no energy
++	 * saving at this point, at least try to
++	 * use cpu affain.
++	 */
++	if (all_non_idle)
++		return -1;
++
 +	return target;
 +}
 +