openrisc: Work around potential relocation issues

When reset code is in flash, the jump instructions emitted by the
compiler are relative instead of absolute jumps.

A fix to the reset code to make correct jumps to the beginning of
code relocated to RAM have also been added.

Signed-off-by: Julius Baxter <juliusbaxter@gmail.com>

diff --git a/arch/openrisc/cpu/cpu.c b/arch/openrisc/cpu/cpu.c
index 25cd6249d2bc0915be6d7912192ce85bfb48a5a1..73ecc6f766ffd06d9adf3b82f485020efc60a59d 100644 (file)
--- a/arch/openrisc/cpu/cpu.c
+++ b/arch/openrisc/cpu/cpu.c
@@ -151,7 +151,11 @@ extern void __reset(void);
 int do_reset(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
        disable_interrupts();
-       __reset();
+       /* Code the jump to __reset here as the compiler is prone to
+          emitting a bad jump instruction if the function is in flash */
+       __asm__("l.movhi r1,hi(__reset);  \
+                 l.ori r1,r1,lo(__reset); \
+                 l.jr r1");
        /* not reached, __reset does not return */
        return 0;
 }

diff --git a/arch/openrisc/cpu/start.S b/arch/openrisc/cpu/start.S
index 3a4271750e81a2fb107c18bda6ec06ea2999eeee..39c80e134fceab6026788fadd07df5195139cf88 100644 (file)
--- a/arch/openrisc/cpu/start.S
+++ b/arch/openrisc/cpu/start.S
@@ -26,8 +26,11 @@
 
 #define HANDLE_EXCEPTION                       \
        l.addi  r1, r1, -EXCEPTION_STACK_SIZE   ;\
+       l.sw    0x00(r1), r2                    ;\
        l.sw    0x1c(r1), r9                    ;\
-       l.jal   _exception_handler              ;\
+       l.movhi r2,hi(_exception_handler)       ;\
+       l.ori   r2,r2,lo(_exception_handler)    ;\
+       l.jalr  r2                              ;\
         l.nop                                  ;\
        l.lwz   r9, 0x1c(r1)                    ;\
        l.addi  r1, r1, EXCEPTION_STACK_SIZE    ;\
@@ -79,8 +82,9 @@ __reset:
        l.bnf   .L_relocvectors
         l.addi r4,r4, 4
 #endif
-
-       l.j     _start
+       l.movhi r4,hi(_start)
+       l.ori   r4,r4,lo(_start)
+       l.jr    r4
         l.nop
 
        /* bus error */
@@ -262,8 +266,7 @@ _start:
        .type   _exception_handler,@function
 
 _exception_handler:
-       /* Store state (r9 already saved)*/
-       l.sw    0x00(r1), r2
+       /* Store state (r2 and r9 already saved)*/
        l.sw    0x04(r1), r3
        l.sw    0x08(r1), r4
        l.sw    0x0c(r1), r5