[RFC PATCH 1/1] arm: add invalidate_dcache_all() after disable cache

[Emanuele Ghidoli]

From: Emanuele Ghidoli <emanuele.ghidoli at toradex.com>

On Cortex-R5 flushing and disabling cache is not enough to avoid
cache and memory incoherence.

In particular, when the cache is enabled after a disable, and if there
are entry in the cache the value from the cache is used instead of the
value from the memory. This, in particular, lead to stack corruption if
the stack is in a cached area.

The commit 44df5e8d30a2 ("arm: move flush_dcache_all() to just before disable cache")
already states that following a cache disable an invalidate is expected
to be done but without coping with cache enable. So just add it explicitly.

Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli at toradex.com>
---
 arch/arm/lib/cache-cp15.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/lib/cache-cp15.c b/arch/arm/lib/cache-cp15.c
index 0893915b3004..2921277d69e0 100644
--- a/arch/arm/lib/cache-cp15.c
+++ b/arch/arm/lib/cache-cp15.c
@@ -254,7 +254,15 @@ static void cache_disable(uint32_t cache_bit)
 	if (cache_bit == CR_C)
 #endif
 		flush_dcache_all();
+
 	set_cr(reg & ~cache_bit);
+
+#ifdef CONFIG_SYS_ARM_MMU
+	if (cache_bit == (CR_C | CR_M))
+#elif defined(CONFIG_SYS_ARM_MPU)
+	if (cache_bit == CR_C)
+#endif
+		invalidate_dcache_all();
 }
 #endif
 
-- 
2.34.1