Subject: [PATCH v2 2/2] Revert "ARM: 8857/1: efi: enable CP15 DMB instructions before cleaning the cache"

From: Ard Biesheuvel <[email-masked]>
Date: Mon, 18 Nov 2019 19:15:43 +0100

This reverts commit e17b1af96b2afc38e684aa2f1033387e2ed10029, which is
no longer necessary now that the v7 specific routines take care not to
issue CP15 barrier instructions before they are enabled in SCTLR.

Acked-by: Marc Zyngier <[email-masked]>
Reviewed-by: Linus Walleij <[email-masked]>
Signed-off-by: Ard Biesheuvel <[email-masked]>
---
 arch/arm/boot/compressed/head.S | 16 +---------------
 1 file changed, 1 insertion(+), 15 deletions(-)

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 1af62baf7cd5..9fe90c71f373 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -1460,21 +1460,7 @@ ENTRY(efi_stub_entry)
 
 		@ Preserve return value of efi_entry() in r4
 		mov	r4, r0
-
-		@ 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_clean_flush
 		bl	cache_off
 
 		@ Set parameters for booting zImage according to boot protocol
-- 
2.20.1

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