[ARM] nommu: provide a way for correct control register value selection

Most MMU-based CPUs have a restriction on the setting of the data cache
enable and mmu enable bits in the control register, whereby if the data
cache is enabled, the MMU must also be enabled.  Enabling the data
cache without the MMU is an invalid combination.

However, there are CPUs where the data cache can be enabled without the
MMU.

In order to allow these CPUs to take advantage of that, provide a
method whereby each proc-*.S file defines the control regsiter value
for use with nommu (with the MMU disabled.)  Later on, when we add
support for enabling the MMU on these devices, we can adjust the
"crval" macro to also enable the data cache for nommu.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 6 insertions, 9 deletions

diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S
index ca13d4d05f6..f0075f1b1fc 100644
--- a/arch/arm/mm/proc-v6.S
+++ b/arch/arm/mm/proc-v6.S
@@ -212,11 +212,11 @@ __v6_setup:
 	orr	r0, r0, #(0xf << 20)
 	mcr	p15, 0, r0, c1, c0, 2		@ Enable full access to VFP
 #endif
+	adr	r5, v6_crval
+	ldmia	r5, {r5, r6}
 	mrc	p15, 0, r0, c1, c0, 0		@ read control register
-	ldr	r5, v6_cr1_clear		@ get mask for bits to clear
 	bic	r0, r0, r5			@ clear bits them
-	ldr	r5, v6_cr1_set			@ get mask for bits to set
-	orr	r0, r0, r5			@ set them
+	orr	r0, r0, r6			@ set them
 	mov	pc, lr				@ return to head.S:__ret
 
 	/*
@@ -225,12 +225,9 @@ __v6_setup:
 	 * rrrr rrrx xxx0 0101 xxxx xxxx x111 xxxx < forced
 	 *         0 110       0011 1.00 .111 1101 < we want
 	 */
-	.type	v6_cr1_clear, #object
-	.type	v6_cr1_set, #object
-v6_cr1_clear:
-	.word	0x01e0fb7f
-v6_cr1_set:
-	.word	0x00c0387d
+	.type	v6_crval, #object
+v6_crval:
+	crval	clear=0x01e0fb7f, mmuset=0x00c0387d, ucset=0x00c0187c
 
 	.type	v6_processor_functions, #object
 ENTRY(v6_processor_functions)