sh: Cleanup and document register bank usage.

Initial register bank cleanup. Make SR.RB configurable, and add some
preliminary documentation on register bank usage within the kernel.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

2 files changed, 31 insertions, 3 deletions

diff --git a/include/asm-sh/system.h b/include/asm-sh/system.h
index 1630a5411e5..198d17e3069 100644
--- a/include/asm-sh/system.h
+++ b/include/asm-sh/system.h
@@ -136,7 +136,8 @@ extern void __xchg_called_with_bad_pointer(void);
 #define set_mb(var, value) do { xchg(&var, value); } while (0)
 
 /* Interrupt Control */
-static __inline__ void local_irq_enable(void)
+#ifdef CONFIG_CPU_HAS_SR_RB
+static inline void local_irq_enable(void)
 {
 	unsigned long __dummy0, __dummy1;
 
@@ -149,6 +150,20 @@ static __inline__ void local_irq_enable(void)
 			     : "1" (~0x000000f0)
 			     : "memory");
 }
+#else
+static inline void local_irq_enable(void)
+{
+	unsigned long __dummy0, __dummy1;
+
+	__asm__ __volatile__ (
+		"stc	sr, %0\n\t"
+		"and	%1, %0\n\t"
+		"ldc	%0, sr\n\t"
+		: "=&r" (__dummy0), "=r" (__dummy1)
+		: "1" (~0x000000f0)
+		: "memory");
+}
+#endif
 
 static __inline__ void local_irq_disable(void)
 {
diff --git a/include/asm-sh/thread_info.h b/include/asm-sh/thread_info.h
index 7345350d98c..f64dd803a01 100644
--- a/include/asm-sh/thread_info.h
+++ b/include/asm-sh/thread_info.h
@@ -48,16 +48,29 @@ struct thread_info {
 #define init_thread_info	(init_thread_union.thread_info)
 #define init_stack		(init_thread_union.stack)
 
+#define THREAD_SIZE (2*PAGE_SIZE)
+
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
 	struct thread_info *ti;
+#ifdef CONFIG_CPU_HAS_SR_RB
 	__asm__("stc	r7_bank, %0" : "=r" (ti));
+#else
+	unsigned long __dummy;
+
+	__asm__ __volatile__ (
+		"mov	r15, %0\n\t"
+		"and	%1, %0\n\t"
+		: "=&r" (ti), "=r" (__dummy)
+		: "1" (~(THREAD_SIZE - 1))
+		: "memory");
+#endif
+
 	return ti;
 }
 
 /* thread information allocation */
-#define THREAD_SIZE (2*PAGE_SIZE)
 #define alloc_thread_info(ti) ((struct thread_info *) __get_free_pages(GFP_KERNEL,1))
 #define free_thread_info(ti) free_pages((unsigned long) (ti), 1)
 
@@ -65,7 +78,7 @@ static inline struct thread_info *current_thread_info(void)
 
 /* how to get the thread information struct from ASM */
 #define GET_THREAD_INFO(reg) \
-	stc	r7_bank, reg
+	stc     r7_bank, reg
 
 #endif