ARM: SMP enable of cache maintanence broadcast

Russell King · Russell King · commit 0fc03d4c8761 · 2016-04-01T23:27:47.000+01:00
Masahiro Yamada reports that we can fail to set the FW bit in the
auxiliary control register, which enables broadcasting the cache
maintanence operations.  This occurs because we only check that the
SMP/nAMP bit is set, rather than checking whether all the bits we
want to be set are set.

Rearrange the code to ensure that all desired bits are set, and only
update the register if we discover some required bits are not set.

Tested-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
@@ -281,12 +281,12 @@ __v7_ca17mp_setup:
 	bl      v7_invalidate_l1
 	ldmia	r12, {r1-r6, lr}
 #ifdef CONFIG_SMP
+	orr	r10, r10, #(1 << 6)		@ Enable SMP/nAMP mode
 	ALT_SMP(mrc	p15, 0, r0, c1, c0, 1)
-	ALT_UP(mov	r0, #(1 << 6))		@ fake it for UP
-	tst	r0, #(1 << 6)			@ SMP/nAMP mode enabled?
-	orreq	r0, r0, #(1 << 6)		@ Enable SMP/nAMP mode
-	orreq	r0, r0, r10			@ Enable CPU-specific SMP bits
-	mcreq	p15, 0, r0, c1, c0, 1
+	ALT_UP(mov	r0, r10)		@ fake it for UP
+	orr	r10, r10, r0			@ Set required bits
+	teq	r10, r0				@ Were they already set?
+	mcrne	p15, 0, r10, c1, c0, 1		@ No, update register
 #endif
 	b	__v7_setup_cont
 
