[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-arm720.S b/arch/arm/mm/proc-arm720.S
index 86102467d37f..b22bc3af232e 100644
--- a/arch/arm/mm/proc-arm720.S
+++ b/arch/arm/mm/proc-arm720.S
@@ -169,11 +169,11 @@ __arm720_setup:
 #ifdef CONFIG_MMU
         mcr     p15, 0, r0, c8, c7, 0           @ flush TLB (v4)
 #endif
+        adr     r5, arm720_crval
+        ldmia   r5, {r5, r6}
         mrc     p15, 0, r0, c1, c0              @ get control register
-        ldr     r5, arm720_cr1_clear
         bic     r0, r0, r5
-        ldr     r5, arm720_cr1_set
-        orr     r0, r0, r5
+        orr     r0, r0, r6
         mov     pc, lr                          @ __ret (head.S)
         .size   __arm720_setup, . - __arm720_setup
 
@@ -183,12 +183,9 @@ __arm720_setup:
          * ..1. 1001 ..11 1101
          * 
          */
-        .type   arm720_cr1_clear, #object
-        .type   arm720_cr1_set, #object
-arm720_cr1_clear:
-        .word   0x2f3f
-arm720_cr1_set:
-        .word   0x213d
+        .type   arm720_crval, #object
+arm720_crval:
+        crval   clear=0x00002f3f, mmuset=0x0000213d, ucset=0x00000130
 
                 __INITDATA