Blackfin arch: allow people to select the feature that is unavailable to the kernel

 - allow people to select the feature that is unavailable to the kernel: NMI, JTAG, or CYCLES.
 - change default NMI handler to simply dump hardware trace buffer.
 - remove default NMI handler completely as calling into kernel code is not safe
   move example handler to wiki so people dont haphazardly copy and paste this stuff thinking its safe

Signed-off-by: Mike Frysinger <michael.frysinger@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

1 files changed, 13 insertions, 5 deletions

diff --git a/arch/blackfin/mach-common/entry.S b/arch/blackfin/mach-common/entry.S
index ab278a72f282..2188f81c6456 100644
--- a/arch/blackfin/mach-common/entry.S
+++ b/arch/blackfin/mach-common/entry.S
@@ -58,6 +58,14 @@
 
 #include <asm/mach-common/context.S>
 
+#if defined(CONFIG_BFIN_SCRATCH_REG_RETN)
+# define EX_SCRATCH_REG RETN
+#elif defined(CONFIG_BFIN_SCRATCH_REG_RETE)
+# define EX_SCRATCH_REG RETE
+#else
+# define EX_SCRATCH_REG CYCLES
+#endif
+
 #ifdef CONFIG_EXCPT_IRQ_SYSC_L1
 .section .l1.text
 #else
@@ -93,7 +101,7 @@ ENTRY(_ex_icplb)
         call __cplb_hdr;
         DEBUG_START_HWTRACE(p5, r7)
         RESTORE_ALL_SYS
-        SP = RETN;
+        SP = EX_SCRATCH_REG;
         rtx;
 ENDPROC(_ex_icplb)
 
@@ -102,7 +110,7 @@ ENTRY(_ex_syscall)
         (R7:6,P5:4) = [sp++];
         ASTAT = [sp++];
         raise 15;               /* invoked by TRAP #0, for sys call */
-        sp = retn;
+        sp = EX_SCRATCH_REG;
         rtx
 ENDPROC(_ex_syscall)
 
@@ -145,7 +153,7 @@ _return_from_exception:
 #endif
         (R7:6,P5:4) = [sp++];
         ASTAT = [sp++];
-        sp = retn;
+        sp = EX_SCRATCH_REG;
         rtx;
 ENDPROC(_ex_soft_bp)
 
@@ -204,7 +212,7 @@ ENTRY(_ex_trap_c)
         DEBUG_START_HWTRACE(p5, r7)
         (R7:6,P5:4) = [sp++];
         ASTAT = [sp++];
-        SP = RETN;
+        SP = EX_SCRATCH_REG;
         raise 5;
         rtx;
 ENDPROC(_ex_trap_c)
@@ -279,7 +287,7 @@ ENTRY(_trap) /* Exception: 4th entry into system event table(supervisor mode)*/
          * covered by a CPLB.  Switch to an exception stack; use RETN as a
          * scratch register (for want of a better option).
          */
-        retn = sp;
+        EX_SCRATCH_REG = sp;
         sp.l = _exception_stack_top;
         sp.h = _exception_stack_top;
         /* Try to deal with syscalls quickly.  */