Re: [PATCH 3/4] MIPS: deal with larger physical offset

[David Daney <ddaney@caviumnetworks.com>]

Florian Fainelli wrote:
> AR7 has a larger physical offset than other MIPS based
> systems and therefore needs to setup handlers differently.
> This version uses uasm instead of the hand crafted assembly
> previously sent. This modification is also required for
> running the kernel in mapped address space.
> 
> Signed-off-by: David Daney <ddaney@caviumnetworks.com>
> Signed-off-by: Eugene Konev <ejka@imfi.kspu.ru>
> Signed-off-by: Florian Fainelli <florian@openwrt.org>
> ---
> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
> index 308e434..dbf52ab 100644
> --- a/arch/mips/kernel/traps.c
> +++ b/arch/mips/kernel/traps.c
> @@ -51,6 +51,8 @@
>  #include <asm/stacktrace.h>
>  #include <asm/irq.h>
>  
> +#include "../mm/uasm.h"
> +


The first time this came up, it was suggested that uasm.h move to 
asm/uasm.h so that we don't have this ugliness.  I think it is still a 
good idea.

>  extern void check_wait(void);
>  extern asmlinkage void r4k_wait(void);
>  extern asmlinkage void rollback_handle_int(void);
> @@ -1283,9 +1285,18 @@ void *set_except_vector(int n, void *addr)
>  
>  	exception_handlers[n] = handler;
>  	if (n == 0 && cpu_has_divec) {
> -		*(u32 *)(ebase + 0x200) = 0x08000000 |
> -					  (0x03ffffff & (handler >> 2));
> -		local_flush_icache_range(ebase + 0x200, ebase + 0x204);
> +		unsigned long jump_mask = ~((1 << 28) - 1);
> +		u32 *buf = (u32 *)(ebase + 0x200);
> +		unsigned int k0 = 26;
> +		if((handler & jump_mask) == ((ebase + 0x200) & jump_mask)) {
> +			uasm_i_j(&buf, handler & jump_mask);
> +			uasm_i_nop(&buf);
> +		} else {
> +			UASM_i_LA(&buf, k0, handler);
> +			uasm_i_jr(&buf, k0);
> +			uasm_i_nop(&buf);
> +		}
> +		local_flush_icache_range(ebase + 0x200, (unsigned long)buf);


I would expect that this causes section mismatch build warnings.

You may have to make this function __init or __cpu_init (and change 
trap_init() to __cpu_init too).

You should also fix the comment, as after the patch it is no longer 
accurate.

>  	}
>  	return (void *)old_handler;
>  }
> 
>