[PATCH] ARM: ARMv5: make PTE_SMALL_AP_UNO_SRO work

[Sascha Hauer <s.hauer@pengutronix.de>]

On ARMv4/5 we have the SCTLR.S and SCTLR.R bits. We set the former which
is deprecated and has implementation defined behaviour on ARMv5. We
clear the latter which has the effect that AP=0b00 as used in PTE_SMALL_AP_UNO_SRO
means "no access".

Clear SCTLR.S and set SCTLR.R instead. With this AP=0b00 maps to
read-only access as intended.

Do not touch any of these bits for >= ARMv6 as both are reserved there.

Fixes: 5916385fae ("ARM: MMU: map text segment ro and data segments execute never")
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 arch/arm/cpu/lowlevel_32.S | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm/cpu/lowlevel_32.S b/arch/arm/cpu/lowlevel_32.S
index 3b1dea5c67..517cefa7b4 100644
--- a/arch/arm/cpu/lowlevel_32.S
+++ b/arch/arm/cpu/lowlevel_32.S
@@ -59,7 +59,7 @@ THUMB(	orr	r12, r12, #PSR_T_BIT	)
 	/* disable MMU stuff and data/unified caches */
 	mrc	p15, 0, r12, c1, c0, 0		/* SCTLR */
 	bic	r12, r12, #(CR_M | CR_C | CR_B)
-	bic	r12, r12, #(CR_S | CR_R | CR_V)
+	bic	r12, r12, #CR_V
 
 #ifndef CONFIG_ARCH_IMX_EXTERNAL_BOOT_NAND
 	/* enable instruction cache */
@@ -70,7 +70,8 @@ THUMB(	orr	r12, r12, #PSR_T_BIT	)
 	orr	r12, r12, #CR_U
 	bic	r12, r12, #CR_A
 #else
-	orr	r12, r12, #CR_S
+	bic	r12, r12, #CR_S
+	orr	r12, r12, #CR_R
 	orr	r12, r12, #CR_A
 #endif
 
-- 
2.47.3