Patchwork [U-Boot] openrisc: Work around potential relocation issues

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Submitter Julius Baxter
Date May 5, 2012, 10:32 p.m.
Message ID <1336257131-29747-1-git-send-email-juliusbaxter@gmail.com>
Download mbox | patch
Permalink /patch/157055/
State Accepted
Commit 3874a377451e4d1f45710f5bf801dd96e8b8f67e
Headers show

Comments

Julius Baxter - May 5, 2012, 10:32 p.m.
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>
---
 arch/openrisc/cpu/cpu.c   |    6 +++++-
 arch/openrisc/cpu/start.S |   13 ++++++++-----
 2 files changed, 13 insertions(+), 6 deletions(-)
Mike Frysinger - May 14, 2012, 5:21 a.m.
On Saturday 05 May 2012 18:32:11 Julius Baxter wrote:
> 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.

please line wrap your commit messages to ~75 chars
-mike
Wolfgang Denk - Aug. 9, 2012, 9:38 p.m.
Dear Julius Baxter,

In message <1336257131-29747-1-git-send-email-juliusbaxter@gmail.com> you wrote:
> 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>
> ---
>  arch/openrisc/cpu/cpu.c   |    6 +++++-
>  arch/openrisc/cpu/start.S |   13 ++++++++-----
>  2 files changed, 13 insertions(+), 6 deletions(-)

Applied, thanks.

Best regards,

Wolfgang Denk

Patch

diff --git a/arch/openrisc/cpu/cpu.c b/arch/openrisc/cpu/cpu.c
index 25cd624..73ecc6f 100644
--- 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 3a42717..39c80e1 100644
--- 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