[PATCH v2 1/3] ARM: cpu: suppress arm_early_mmu_cache_invalidate if dcache enabled

[Ahmad Fatoum]

barebox built as EFI payload on ARM invalidates the data caches inside
barebox_arm_entry(), which may lead to memory corruption.

Generally, calling arm_early_mmu_cache_invalidate() while the caches are
enabled is a bad idea, so add a function that protects against that and
use it in common code.

Fixes: 742e78976dd4 ("ARM64: add optional EFI stub")
Signed-off-by: Ahmad Fatoum <a.fat...@pengutronix.de>
---
v1 -> v2:
  - rename dcache_invalidate_stale(to cache_invalidate_stale (Lucas)
---
 arch/arm/cpu/common.c        | 16 ++++++++++++++++
 arch/arm/cpu/entry_ll_32.S   |  2 +-
 arch/arm/cpu/entry_ll_64.S   |  2 +-
 arch/arm/include/asm/cache.h |  3 +++
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
index adb5d6a02bc8..e079f55b8bb7 100644
--- a/arch/arm/cpu/common.c
+++ b/arch/arm/cpu/common.c
@@ -37,6 +37,22 @@ void sync_caches_for_execution(void)
        arm_early_mmu_cache_flush();
 }
 
+/**
+ * cache_invalidate_stale - invalidate caches prior to enabling them
+ *
+ * Some SoCs can come up with invalid entries, but with the valid bit set.
+ * This function discards them, as that would lead to memory corruption
+ * otherwise.
+ */
+void cache_invalidate_stale(void)
+{
+       /* if caches are already enabled, don't cause data loss */
+       if (get_cr() & CR_C)
+               return;
+
+       arm_early_mmu_cache_invalidate();
+}
+
 void pbl_barebox_break(void)
 {
        __asm__ __volatile__ (
diff --git a/arch/arm/cpu/entry_ll_32.S b/arch/arm/cpu/entry_ll_32.S
index 0d4c47c1c870..0763581fded4 100644
--- a/arch/arm/cpu/entry_ll_32.S
+++ b/arch/arm/cpu/entry_ll_32.S
@@ -15,7 +15,7 @@ ENTRY(__barebox_arm_entry)
        mov     r4, r0
        mov     r5, r1
        mov     r6, r2
-       bl      arm_early_mmu_cache_invalidate
+       bl      cache_invalidate_stale
        mov     r0, r4
        mov     r1, r5
        mov     r2, r6
diff --git a/arch/arm/cpu/entry_ll_64.S b/arch/arm/cpu/entry_ll_64.S
index 5eb6efed5baf..c80a23c6506d 100644
--- a/arch/arm/cpu/entry_ll_64.S
+++ b/arch/arm/cpu/entry_ll_64.S
@@ -15,7 +15,7 @@ ENTRY(__barebox_arm_entry)
        mov     x19, x0
        mov     x20, x1
        mov     x21, x2
-       bl      arm_early_mmu_cache_invalidate
+       bl      cache_invalidate_stale
        mov     x0, x19
        mov     x1, x20
        mov     x2, x21
diff --git a/arch/arm/include/asm/cache.h b/arch/arm/include/asm/cache.h
index ea78ae123aec..9dbf433356b9 100644
--- a/arch/arm/include/asm/cache.h
+++ b/arch/arm/include/asm/cache.h
@@ -26,6 +26,9 @@ static inline void icache_invalidate(void)
 #endif
 }
 
+
+void cache_invalidate_stale(void);
+
 void arm_early_mmu_cache_flush(void);
 void arm_early_mmu_cache_invalidate(void);
 
-- 
2.47.3