ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+

ARMv6 and greater introduced a new instruction ("bx") which can be used
to return from function calls.  Recent CPUs perform better when the
"bx lr" instruction is used rather than the "mov pc, lr" instruction,
and this sequence is strongly recommended to be used by the ARM
architecture manual (section A.4.1.1).

We provide a new macro "ret" with all its variants for the condition
code which will resolve to the appropriate instruction.

Rather than doing this piecemeal, and miss some instances, change all
the "mov pc" instances to use the new macro, with the exception of
the "movs" instruction and the kprobes code.  This allows us to detect
the "mov pc, lr" case and fix it up - and also gives us the possibility
of deploying this for other registers depending on the CPU selection.

Reported-by: Will Deacon <will.deacon@arm.com>
Tested-by: Stephen Warren <swarren@nvidia.com> # Tegra Jetson TK1
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> # mioa701_bootresume.S
Tested-by: Andrew Lunn <andrew@lunn.ch> # Kirkwood
Tested-by: Shawn Guo <shawn.guo@freescale.com>
Tested-by: Tony Lindgren <tony@atomide.com> # OMAPs
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com> # Armada XP, 375, 385
Acked-by: Sekhar Nori <nsekhar@ti.com> # DaVinci
Acked-by: Christoffer Dall <christoffer.dall@linaro.org> # kvm/hyp
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com> # PXA3xx
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> # Xen
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> # ARMv7M
Tested-by: Simon Horman <horms+renesas@verge.net.au> # Shmobile
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 10 insertions, 9 deletions

diff --git a/arch/arm/mm/cache-fa.S b/arch/arm/mm/cache-fa.S
index e505befe51b5..2f0c58836ae7 100644
--- a/arch/arm/mm/cache-fa.S
+++ b/arch/arm/mm/cache-fa.S
@@ -15,6 +15,7 @@
  */
 #include <linux/linkage.h>
 #include <linux/init.h>
+#include <asm/assembler.h>
 #include <asm/memory.h>
 #include <asm/page.h>
 
@@ -45,7 +46,7 @@
 ENTRY(fa_flush_icache_all)
         mov     r0, #0
         mcr     p15, 0, r0, c7, c5, 0           @ invalidate I cache
-        mov     pc, lr
+        ret     lr
 ENDPROC(fa_flush_icache_all)
 
 /*
@@ -71,7 +72,7 @@ __flush_whole_cache:
         mcrne   p15, 0, ip, c7, c5, 6           @ invalidate BTB
         mcrne   p15, 0, ip, c7, c10, 4          @ drain write buffer
         mcrne   p15, 0, ip, c7, c5, 4           @ prefetch flush
-        mov     pc, lr
+        ret     lr
 
 /*
  *      flush_user_cache_range(start, end, flags)
@@ -99,7 +100,7 @@ ENTRY(fa_flush_user_cache_range)
         mcrne   p15, 0, ip, c7, c5, 6           @ invalidate BTB
         mcrne   p15, 0, ip, c7, c10, 4          @ data write barrier
         mcrne   p15, 0, ip, c7, c5, 4           @ prefetch flush
-        mov     pc, lr
+        ret     lr
 
 /*
  *      coherent_kern_range(start, end)
@@ -135,7 +136,7 @@ ENTRY(fa_coherent_user_range)
         mcr     p15, 0, r0, c7, c5, 6           @ invalidate BTB
         mcr     p15, 0, r0, c7, c10, 4          @ drain write buffer
         mcr     p15, 0, r0, c7, c5, 4           @ prefetch flush
-        mov     pc, lr
+        ret     lr
 
 /*
  *      flush_kern_dcache_area(void *addr, size_t size)
@@ -155,7 +156,7 @@ ENTRY(fa_flush_kern_dcache_area)
         mov     r0, #0
         mcr     p15, 0, r0, c7, c5, 0           @ invalidate I cache
         mcr     p15, 0, r0, c7, c10, 4          @ drain write buffer
-        mov     pc, lr
+        ret     lr
 
 /*
  *      dma_inv_range(start, end)
@@ -181,7 +182,7 @@ fa_dma_inv_range:
         blo     1b
         mov     r0, #0
         mcr     p15, 0, r0, c7, c10, 4          @ drain write buffer
-        mov     pc, lr
+        ret     lr
 
 /*
  *      dma_clean_range(start, end)
@@ -199,7 +200,7 @@ fa_dma_clean_range:
         blo     1b
         mov     r0, #0  
         mcr     p15, 0, r0, c7, c10, 4          @ drain write buffer
-        mov     pc, lr
+        ret     lr
 
 /*
  *      dma_flush_range(start,end)
@@ -214,7 +215,7 @@ ENTRY(fa_dma_flush_range)
         blo     1b
         mov     r0, #0  
         mcr     p15, 0, r0, c7, c10, 4          @ drain write buffer
-        mov     pc, lr
+        ret     lr
 
 /*
  *      dma_map_area(start, size, dir)
@@ -237,7 +238,7 @@ ENDPROC(fa_dma_map_area)
  *      - dir   - DMA direction
  */
 ENTRY(fa_dma_unmap_area)
-        mov     pc, lr
+        ret     lr
 ENDPROC(fa_dma_unmap_area)
 
         .globl  fa_flush_kern_cache_louis