[U-Boot] [PATCH v2] nios2: fix out of reach case for do_reset

[Thomas Chou]

There is a limitation (or bug?) of nios2 toolchain. The nios2 gcc
didn't generate correct code when the reset vector is passed as a
constant. It just generated a direct "call", which was wrong when
the reset vector was not located in the same 256MB span as u-boot.

The "Nios II Processor Reference Handbook" said,
"call can transfer execution anywhere within the 256 MByte range
determined by PC31..28. The Nios II GNU linker does not automatically
handle cases in which the address is out of this range."

So we have to use registered "callr" instruction to do the job.

Signed-off-by: Thomas Chou <thomas at wytron.com.tw>
---
v2, add a macro for the inlince asm nios2_callr.

 arch/nios2/cpu/cpu.c            |   11 +++++------
 arch/nios2/include/asm/system.h |    5 +++++
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/nios2/cpu/cpu.c b/arch/nios2/cpu/cpu.c
index 6379534..d9c6544 100644
--- a/arch/nios2/cpu/cpu.c
+++ b/arch/nios2/cpu/cpu.c
@@ -40,11 +40,10 @@ int checkcpu (void)
 	return (0);
 }
 
-
-int do_reset (void)
+int do_reset(void)
 {
-	void (*rst)(void) = (void(*)(void))CONFIG_SYS_RESET_ADDR;
-	disable_interrupts ();
-	rst();
-	return(0);
+	disable_interrupts();
+	/* indirect call to go beyond 256MB limitation of toolchain */
+	nios2_callr(CONFIG_SYS_RESET_ADDR);
+	return 0;
 }
diff --git a/arch/nios2/include/asm/system.h b/arch/nios2/include/asm/system.h
index bb03ca5..086d92b 100644
--- a/arch/nios2/include/asm/system.h
+++ b/arch/nios2/include/asm/system.h
@@ -56,4 +56,9 @@
 	((flags & NIOS2_STATUS_PIE_MSK) == 0x0);	\
 })
 
+/* indirect call to go beyond 256MB limitation of toolchain */
+#define nios2_callr(addr) __asm__ __volatile__ (	\
+	"callr	%0"					\
+	: : "r" (addr))
+
 #endif /* __ASM_NIOS2_SYSTEM_H */
-- 
1.7.2.1