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>

1 files changed, 15 insertions, 2 deletions

diff --git a/include/asm-sh/thread_info.h b/include/asm-sh/thread_info.h
index 7345350d98c0..f64dd803a014 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