ARMv7: Document the PRRR and NMRR registers setting

This patch adds a comment to the proc-v7.S file for the setting of the
PRRR and NMRR registers. It also sets the PRRR[13:12] bits to 0
(corresponding to the reserved TEX[0]CB encoding 110) to be consistent
with the documentation.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 30 insertions, 2 deletions

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 095b69f5a83..0a8ffd3c03f 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -219,8 +219,36 @@ __v7_setup:
         mov     r10, #0x1f                      @ domains 0, 1 = manager
         mcr     p15, 0, r10, c3, c0, 0          @ load domain access register
 #endif
-        ldr     r5, =0xff0aa1a8
-        ldr     r6, =0x40e040e0
+        /*
+         * Memory region attributes with SCTLR.TRE=1
+         *
+         *   n = TEX[0],C,B
+         *   TR = PRRR[2n+1:2n]         - memory type
+         *   IR = NMRR[2n+1:2n]         - inner cacheable property
+         *   OR = NMRR[2n+17:2n+16]     - outer cacheable property
+         *
+         *                      n       TR      IR      OR
+         *   UNCACHED           000     00
+         *   BUFFERABLE         001     10      00      00
+         *   WRITETHROUGH       010     10      10      10
+         *   WRITEBACK          011     10      11      11
+         *   reserved           110
+         *   WRITEALLOC         111     10      01      01
+         *   DEV_SHARED         100     01
+         *   DEV_NONSHARED      100     01
+         *   DEV_WC             001     10
+         *   DEV_CACHED         011     10
+         *
+         * Other attributes:
+         *
+         *   DS0 = PRRR[16] = 0         - device shareable property
+         *   DS1 = PRRR[17] = 1         - device shareable property
+         *   NS0 = PRRR[18] = 0         - normal shareable property
+         *   NS1 = PRRR[19] = 1         - normal shareable property
+         *   NOS = PRRR[24+n] = 1       - not outer shareable
+         */
+        ldr     r5, =0xff0a81a8                 @ PRRR
+        ldr     r6, =0x40e040e0                 @ NMRR
         mcr     p15, 0, r5, c10, c2, 0          @ write PRRR
         mcr     p15, 0, r6, c10, c2, 1          @ write NMRR
         adr     r5, v7_crval