[RFC PATCH v2 4/5] ARM: kernel: update __cpu_disable to use cache LoUIS maintenance API

[Lorenzo Pieralisi]

When a CPU is hotplugged out caches that reside in its power domain
lose their contents and so must be cleaned to the next memory level.

Currently, __cpu_disable calls flush_cache_all() that for new generation
processor like A15/A7 ends up cleaning and invalidating all cache levels
up to Level of Coherency, which includes the unified L2.

This ends up being a waste of cycles since the L2 cache contents are not
lost on power down.

This patch updates __cpu_disable to use the new LoUIS API cache operations.

Reviewed-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
---
 arch/arm/kernel/smp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index d3eb222..f44e9cd 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -136,8 +136,11 @@ int __cpu_disable(void)
 	/*
 	 * Flush user cache and TLB mappings, and then remove this CPU
 	 * from the vm mask set of all processes.
+	 *
+	 * Caches are flushed to the Level of Unification Inner Shareable
+	 * to write-back dirty lines to unified caches shared by all CPUs.
 	 */
-	flush_cache_all();
+	flush_cache_louis();
 	local_flush_tlb_all();
 
 	clear_tasks_mm_cpumask(cpu);
-- 
1.7.12