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

[Scott McNutt]

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 <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 */