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>

4 files changed, 66 insertions, 46 deletions

diff --git a/arch/arm/include/asm/fiq.h b/arch/arm/include/asm/fiq.h
index 2242ce22ec6c..45bb3eeeab7c 100644
--- a/arch/arm/include/asm/fiq.h
+++ b/arch/arm/include/asm/fiq.h
@@ -29,9 +29,21 @@ struct fiq_handler {
 extern int claim_fiq(struct fiq_handler *f);
 extern void release_fiq(struct fiq_handler *f);
 extern void set_fiq_handler(void *start, unsigned int length);
-extern void set_fiq_regs(struct pt_regs *regs);
-extern void get_fiq_regs(struct pt_regs *regs);
 extern void enable_fiq(int fiq);
 extern void disable_fiq(int fiq);
 
+/* helpers defined in fiqasm.S: */
+extern void __set_fiq_regs(unsigned long const *regs);
+extern void __get_fiq_regs(unsigned long *regs);
+
+static inline void set_fiq_regs(struct pt_regs const *regs)
+{
+        __set_fiq_regs(&regs->ARM_r8);
+}
+
+static inline void get_fiq_regs(struct pt_regs *regs)
+{
+        __get_fiq_regs(&regs->ARM_r8);
+}
+
 #endif
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 8d95446150a3..01c0292eea8b 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -24,7 +24,7 @@ obj-$(CONFIG_OC_ETM)		+= etm.o
 
 obj-$(CONFIG_ISA_DMA_API)       += dma.o
 obj-$(CONFIG_ARCH_ACORN)        += ecard.o 
-obj-$(CONFIG_FIQ)               += fiq.o
+obj-$(CONFIG_FIQ)               += fiq.o fiqasm.o
 obj-$(CONFIG_MODULES)           += armksyms.o module.o
 obj-$(CONFIG_ARTHUR)            += arthur.o
 obj-$(CONFIG_ISA_DMA)           += dma-isa.o
diff --git a/arch/arm/kernel/fiq.c b/arch/arm/kernel/fiq.c
index e72dc34eea1c..4c164ece5891 100644
--- a/arch/arm/kernel/fiq.c
+++ b/arch/arm/kernel/fiq.c
@@ -89,47 +89,6 @@ void set_fiq_handler(void *start, unsigned int length)
                 flush_icache_range(0x1c, 0x1c + length);
 }
 
-/*
- * Taking an interrupt in FIQ mode is death, so both these functions
- * disable irqs for the duration.  Note - these functions are almost
- * entirely coded in assembly.
- */
-void __naked set_fiq_regs(struct pt_regs *regs)
-{
-        register unsigned long tmp;
-        asm volatile (
-        "mov    ip, sp\n\
-        stmfd   sp!, {fp, ip, lr, pc}\n\
-        sub     fp, ip, #4\n\
-        mrs     %0, cpsr\n\
-        msr     cpsr_c, %2      @ select FIQ mode\n\
-        mov     r0, r0\n\
-        ldmia   %1, {r8 - r14}\n\
-        msr     cpsr_c, %0      @ return to SVC mode\n\
-        mov     r0, r0\n\
-        ldmfd   sp, {fp, sp, pc}"
-        : "=&r" (tmp)
-        : "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE));
-}
-
-void __naked get_fiq_regs(struct pt_regs *regs)
-{
-        register unsigned long tmp;
-        asm volatile (
-        "mov    ip, sp\n\
-        stmfd   sp!, {fp, ip, lr, pc}\n\
-        sub     fp, ip, #4\n\
-        mrs     %0, cpsr\n\
-        msr     cpsr_c, %2      @ select FIQ mode\n\
-        mov     r0, r0\n\
-        stmia   %1, {r8 - r14}\n\
-        msr     cpsr_c, %0      @ return to SVC mode\n\
-        mov     r0, r0\n\
-        ldmfd   sp, {fp, sp, pc}"
-        : "=&r" (tmp)
-        : "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE));
-}
-
 int claim_fiq(struct fiq_handler *f)
 {
         int ret = 0;
@@ -174,8 +133,8 @@ void disable_fiq(int fiq)
 }
 
 EXPORT_SYMBOL(set_fiq_handler);
-EXPORT_SYMBOL(set_fiq_regs);
-EXPORT_SYMBOL(get_fiq_regs);
+EXPORT_SYMBOL(__set_fiq_regs);  /* defined in fiqasm.S */
+EXPORT_SYMBOL(__get_fiq_regs);  /* defined in fiqasm.S */
 EXPORT_SYMBOL(claim_fiq);
 EXPORT_SYMBOL(release_fiq);
 EXPORT_SYMBOL(enable_fiq);
diff --git a/arch/arm/kernel/fiqasm.S b/arch/arm/kernel/fiqasm.S
new file mode 100644
index 000000000000..207f9d652010
--- /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)