MIPS: Deal with larger physical offsets

AR7 has a larger physical offset than other MIPS based systems and therefore
needs to setup its handlers beyond the usual KSEG0 range. When running the
kernel in mapped mode this modification is also required. Remove function
comment which is now incorrect.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Eugene Konev <ejka@imfi.kspu.ru>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
To: linux-mips@linux-mips.org
To: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/889/
Patchwork: http://patchwork.linux-mips.org/patch/932/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/traps.c

@@ -50,6 +50,7 @@
 #include <asm/types.h>
 #include <asm/stacktrace.h>
 #include <asm/irq.h>
+#include <asm/uasm.h>
 
 extern void check_wait(void);
 extern asmlinkage void r4k_wait(void);
@@ -1271,11 +1272,6 @@ unsigned long ebase;
 unsigned long exception_handlers[32];
 unsigned long vi_handlers[64];
 
-/*
- * As a side effect of the way this is implemented we're limited
- * to interrupt handlers in the address range from
- * KSEG0 <= x < KSEG0 + 256mb on the Nevada.  Oh well ...
- */
 void __init *set_except_vector(int n, void *addr)
 {
 	unsigned long handler = (unsigned long) addr;
@@ -1283,9 +1279,18 @@ void __init *set_except_vector(int n, void *addr)
 
 	exception_handlers[n] = handler;
 	if (n == 0 && cpu_has_divec) {
-		*(u32 *)(ebase + 0x200) = 0x08000000 |
-					  (0x03ffffff & (handler >> 2));
-		local_flush_icache_range(ebase + 0x200, ebase + 0x204);
+		unsigned long jump_mask = ~((1 << 28) - 1);
+		u32 *buf = (u32 *)(ebase + 0x200);
+		unsigned int k0 = 26;
+		if ((handler & jump_mask) == ((ebase + 0x200) & jump_mask)) {
+			uasm_i_j(&buf, handler & ~jump_mask);
+			uasm_i_nop(&buf);
+		} else {
+			UASM_i_LA(&buf, k0, handler);
+			uasm_i_jr(&buf, k0);
+			uasm_i_nop(&buf);
+		}
+		local_flush_icache_range(ebase + 0x200, (unsigned long)buf);
 	}
 	return (void *)old_handler;
 }