ARM: 6938/1: fiq: Refactor {get,set}_fiq_regs() for Thumb-2
* To remove the risk of inconvenient register allocation decisions
by the compiler, these functions are separated out as pure
assembler.
* The apcs frame manipulation code is not applicable for Thumb-2
(and also not easily compatible). Since it's not essential to
have a full frame on these leaf assembler functions, the frame
manipulation is removed, in the interests of simplicity.
* Split up ldm/stm instructions to be compatible with Thumb-2,
as well as avoiding instruction forms deprecated on >= ARMv7.
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Reviewed-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/fiqasm.S b/arch/arm/kernel/fiqasm.S
new file mode 100644
index 0000000..207f9d6
--- /dev/null
+++ b/arch/arm/kernel/fiqasm.S
@@ -0,0 +1,49 @@
+/*
+ * linux/arch/arm/kernel/fiqasm.S
+ *
+ * Derived from code originally in linux/arch/arm/kernel/fiq.c:
+ *
+ * Copyright (C) 1998 Russell King
+ * Copyright (C) 1998, 1999 Phil Blundell
+ * Copyright (C) 2011, Linaro Limited
+ *
+ * FIQ support written by Philip Blundell <philb@gnu.org>, 1998.
+ *
+ * FIQ support re-written by Russell King to be more generic
+ *
+ * v7/Thumb-2 compatibility modifications by Linaro Limited, 2011.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * Taking an interrupt in FIQ mode is death, so both these functions
+ * disable irqs for the duration.
+ */
+
+ENTRY(__set_fiq_regs)
+ mov r2, #PSR_I_BIT | PSR_F_BIT | FIQ_MODE
+ mrs r1, cpsr
+ msr cpsr_c, r2 @ select FIQ mode
+ mov r0, r0 @ avoid hazard prior to ARMv4
+ ldmia r0!, {r8 - r12}
+ ldr sp, [r0], #4
+ ldr lr, [r0]
+ msr cpsr_c, r1 @ return to SVC mode
+ mov r0, r0 @ avoid hazard prior to ARMv4
+ mov pc, lr
+ENDPROC(__set_fiq_regs)
+
+ENTRY(__get_fiq_regs)
+ mov r2, #PSR_I_BIT | PSR_F_BIT | FIQ_MODE
+ mrs r1, cpsr
+ msr cpsr_c, r2 @ select FIQ mode
+ mov r0, r0 @ avoid hazard prior to ARMv4
+ stmia r0!, {r8 - r12}
+ str sp, [r0], #4
+ str lr, [r0]
+ msr cpsr_c, r1 @ return to SVC mode
+ mov r0, r0 @ avoid hazard prior to ARMv4
+ mov pc, lr
+ENDPROC(__get_fiq_regs)