diff options
| author | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-08-28 13:08:14 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-09-26 14:39:54 +0100 |
| commit | 195b58add463f697fb802ed55e26759094d40a54 (patch) | |
| tree | d3523c21a3bb610a87672356770a83c1e3c0ca8d /arch/arm/kernel/entry-armv.S | |
| parent | 8b521cb2947d8811b4cf7fc6a7a6ebde35218243 (diff) | |
ARM: Avoid writing to control register on every exception
If we are not changing the control register value, avoid writing to it.
Writes to the control register can be very expensive, taking around a
hundred cycles or so.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/entry-armv.S')
| -rw-r--r-- | arch/arm/kernel/entry-armv.S | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 36276cdccfbc..3fe61de63e30 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -321,6 +321,9 @@ ENDPROC(__pabt_svc) ARM( stmib sp, {r1 - r12} ) THUMB( stmia sp, {r0 - r12} ) + ATRAP( mrc p15, 0, r7, c1, c0, 0) + ATRAP( ldr r8, .LCcralign) + ldmia r0, {r3 - r5} add r0, sp, #S_PC @ here for interlock avoidance mov r6, #-1 @ "" "" "" "" @@ -328,6 +331,8 @@ ENDPROC(__pabt_svc) str r3, [sp] @ save the "real" r0 copied @ from the exception stack + ATRAP( ldr r8, [r8, #0]) + @ @ We are now ready to fill in the remaining blanks on the stack: @ @@ -341,10 +346,9 @@ ENDPROC(__pabt_svc) ARM( stmdb r0, {sp, lr}^ ) THUMB( store_user_sp_lr r0, r1, S_SP - S_PC ) - @ @ Enable the alignment trap while in kernel mode - @ - alignment_trap r0, .LCcralign + ATRAP( teq r8, r7) + ATRAP( mcrne p15, 0, r8, c1, c0, 0) @ @ Clear FP to mark the first stack frame |