sh: Add support for 4K stacks.

This enables support for 4K stacks on SH.

Currently this depends on DEBUG_KERNEL, but likely all boards
will switch to this as the default in the future.

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

2 files changed, 20 insertions, 1 deletions

diff --git a/include/asm-sh/irq.h b/include/asm-sh/irq.h
index dd05e102fc0e..0e5f365aff70 100644
--- a/include/asm-sh/irq.h
+++ b/include/asm-sh/irq.h
@@ -719,6 +719,15 @@ static inline int generic_irq_demux(int irq)
 #define irq_canonicalize(irq)   (irq)
 #define irq_demux(irq)          __irq_demux(sh_mv.mv_irq_demux(irq))
 
+#ifdef CONFIG_4KSTACKS
+extern void irq_ctx_init(int cpu);
+extern void irq_ctx_exit(int cpu);
+# define __ARCH_HAS_DO_SOFTIRQ
+#else
+# define irq_ctx_init(cpu) do { } while (0)
+# define irq_ctx_exit(cpu) do { } while (0)
+#endif
+
 #if defined(CONFIG_CPU_SUBTYPE_SH73180)
 #include <asm/irq-sh73180.h>
 #endif
diff --git a/include/asm-sh/thread_info.h b/include/asm-sh/thread_info.h
index 605259f88113..3ebc3f9039eb 100644
--- a/include/asm-sh/thread_info.h
+++ b/include/asm-sh/thread_info.h
@@ -9,8 +9,8 @@
  *  Copyright (C) 2002  David Howells (dhowells@redhat.com)
  *  - Incorporating suggestions made by Linus Torvalds and Dave Miller
  */
-
 #ifdef __KERNEL__
+#include <asm/page.h>
 
 #ifndef __ASSEMBLY__
 #include <asm/processor.h>
@@ -23,13 +23,20 @@ struct thread_info {
         int                     preempt_count; /* 0 => preemptable, <0 => BUG */
         mm_segment_t            addr_limit;     /* thread address space */
         struct restart_block    restart_block;
+        unsigned long           previous_sp;    /* sp of previous stack in case
+                                                   of nested IRQ stacks */
         __u8                    supervisor_stack[0];
 };
 
 #endif
 
 #define PREEMPT_ACTIVE          0x10000000
+
+#ifdef CONFIG_4KSTACKS
+#define THREAD_SIZE             (PAGE_SIZE)
+#else
 #define THREAD_SIZE             (PAGE_SIZE * 2)
+#endif
 #define STACK_WARN              (THREAD_SIZE / 8)
 
 /*
@@ -52,6 +59,9 @@ struct thread_info {
 #define init_thread_info        (init_thread_union.thread_info)
 #define init_stack              (init_thread_union.stack)
 
+/* how to get the current stack pointer from C */
+register unsigned long current_stack_pointer asm("r15") __attribute_used__;
+
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {