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

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

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.fatoum@pengutronix.de>
---
 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..d41da73d7e83 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();
 }
 
+/**
+ * dcache_invalidate_stale - invalidate data cache prior to enabling it
+ *
+ * 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 dcache_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..eb1793b54e66 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	dcache_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..3404f6d05802 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	dcache_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..64f369f865db 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 dcache_invalidate_stale(void);
+
 void arm_early_mmu_cache_flush(void);
 void arm_early_mmu_cache_invalidate(void);
 
-- 
2.47.3