On 12:14 Fri 16 May , Amit Kumar wrote:
>
>
> Hello,
>
> Kindly refer code at path UBOOT / u-boot / cpu / pxa /
> start.S
>
>
>
> Code:
>
> .macro irq_save_user_regs
>
> sub sp, sp, #S_FRAME_SIZE
>
> stmia sp, {r0 - r12} /* Calling r0-r12 */
>
> add r8, sp, #S_PC
>
> stmdb r8, {sp, lr}^ /* Calling SP, LR */
>
> str lr, [r8, #0] /* Save calling PC */
>
> mrs r6, spsr
>
> str r6, [r8, #4] /* Save CPSR */
>
> str r0, [r8, #8] /* Save OLD_R0 */
>
> mov r0, sp
>
> .endm
>
>
>
> Why there is need to save R0? If we refer ARM architecture (section what
> all happens when interrupt comes) there is no need to save R0.
>
>
>
> Moreover, there is no need of writing such big piece of code it can be
> replaced with below given four liner code:
>
>
>
> Sub lr, lr, #4
>
> Stmfd sp! , {r0-r12, lr}
>
> MRS r1, spsr
>
> Stmfd sp! , {r1}
>
>
>
> Similarly we can write small code for restore of stack
>
> .macro irq_restore_user_regs
>
> Ldmfd sp! , {r1}
>
> MSR cpsr_c , R1
> ldmfd sp!, {r0-r12, pc}^
>
> .endm
>
>
>
> Can anybody clarify?
I'll take a look, I'm currently cleaning the board init
Please do NOT post as HTML
>
>
>
> Regards
>
> Amit Kumar
>
>
>
>
>
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Please remove this to
Best Regards,
J.
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