Thomas,
Applied to: git://git.denx.de/u-boot-nios.git next
Thanks,
--Scott
Thomas Chou wrote:
> 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 <tho...@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 */
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