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-rw-r--r--arch/arm/boot/compressed/head.S16
1 files changed, 15 insertions, 1 deletions
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 6c7ccb428c07..7135820f76d4 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -1438,7 +1438,21 @@ ENTRY(efi_stub_entry)
@ Preserve return value of efi_entry() in r4
mov r4, r0
- bl cache_clean_flush
+
+ @ our cache maintenance code relies on CP15 barrier instructions
+ @ but since we arrived here with the MMU and caches configured
+ @ by UEFI, we must check that the CP15BEN bit is set in SCTLR.
+ @ Note that this bit is RAO/WI on v6 and earlier, so the ISB in
+ @ the enable path will be executed on v7+ only.
+ mrc p15, 0, r1, c1, c0, 0 @ read SCTLR
+ tst r1, #(1 << 5) @ CP15BEN bit set?
+ bne 0f
+ orr r1, r1, #(1 << 5) @ CP15 barrier instructions
+ mcr p15, 0, r1, c1, c0, 0 @ write SCTLR
+ ARM( .inst 0xf57ff06f @ v7+ isb )
+ THUMB( isb )
+
+0: bl cache_clean_flush
bl cache_off
@ Set parameters for booting zImage according to boot protocol