[ARM] 3352/1: DSB required for the completion of a TLB maintenance operation

Patch from Catalin Marinas

Chapter B2.7.3 in the latest ARM ARM (with v6 information) states that
the completion of a TLB maintenance operation is only guaranteed by
the execution of a DSB (Data Syncronization Barrier, formerly Data
Write Barrier or Drain Write Buffer).

Note that a DSB is only needed in the flush_tlb_kernel_* functions
since the completion is guaranteed by a mode change (i.e. switching
back to user mode) for the flush_tlb_user_* functions.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -78,7 +78,7 @@ menu "System Type"
 
 choice
 	prompt "ARM system type"
-	default ARCH_RPC
+	default ARCH_VERSATILE
 
 config ARCH_CLPS7500
 	bool "Cirrus-CL-PS7500FE"

arch/arm/mm/tlb-v6.S

@@ -80,6 +80,7 @@ ENTRY(v6wbi_flush_kern_tlb_range)
 	add	r0, r0, #PAGE_SZ
 	cmp	r0, r1
 	blo	1b
+	mcr	p15, 0, r2, c7, c10, 4		@ data synchronization barrier
 	mov	pc, lr
 
 	.section ".text.init", #alloc, #execinstr

include/asm-arm/tlbflush.h

@@ -340,6 +340,12 @@ static inline void local_flush_tlb_kernel_page(unsigned long kaddr)
 		asm("mcr%? p15, 0, %0, c8, c6, 1" : : "r" (kaddr));
 	if (tlb_flag(TLB_V6_I_PAGE))
 		asm("mcr%? p15, 0, %0, c8, c5, 1" : : "r" (kaddr));
+
+	/* The ARM ARM states that the completion of a TLB maintenance
+	 * operation is only guaranteed by a DSB instruction
+	 */
+	if (tlb_flag(TLB_V6_U_PAGE | TLB_V6_D_PAGE | TLB_V6_I_PAGE))
+		asm("mcr%? p15, 0, %0, c7, c10, 4" : : "r" (zero));
 }
 
 /*