topic Re: Which registers should I save when saving state in timer interupt handler on mpc8306? in PowerQUICC Processors

Which registers should I save when saving state in timer interupt handler on mpc8306?

maojiu — Tue, 19 Aug 2014 02:25:02 GMT

Which registers should I save when saving state in timer interupt handler on mpc8306? I have saved the following registers:

r0 to r31, srr0,srr1, lr, ctr, cr, xer.

but it seems not working.

Thank you for any help !

Re: Which registers should I save when saving state in timer interupt handler on mpc8306?

yipingwang — Tue, 19 Aug 2014 11:04:24 GMT

Hello mao jiu,

Please refer to the following code from CodeWarrior sample project.

##############################################################################

# isr_prologue

# Saves the necessary registers for an interrupt service routine

##############################################################################

isr_prologue: .macro

stwu rsp,-80(rsp)

stw r0,8(rsp)

mfctr r0

stw r0,12(rsp)

mfxer r0

stw r0,16(rsp)

mfcr r0

stw r0,20(rsp)

mflr r0

stw r0,24(rsp)

stw r3,40(rsp)

stw r4,44(rsp)

stw r5,48(rsp)

stw r6,52(rsp)

stw r7,56(rsp)

stw r8,60(rsp)

stw r9,64(rsp)

stw r10,68(rsp)

stw r11,72(rsp)

stw r12,76(rsp)

mfsrr0 r0

stw r0,28(rsp)

mfsrr1 r0

stw r0,32(rsp)

.endm

##############################################################################

# isr_epilogue

# Restores the necessary registers for an interrupt service routine

##############################################################################

isr_epilogue: .macro

lwz r0,32(rsp)

mtsrr1 r0

lwz r0,28(rsp)

mtsrr0 r0

lwz r3,40(rsp)

lwz r4,44(rsp)

lwz r5,48(rsp)

lwz r6,52(rsp)

lwz r7,56(rsp)

lwz r8,60(rsp)

lwz r9,64(rsp)

lwz r10,68(rsp)

lwz r11,72(rsp)

lwz r12,76(rsp)

lwz r0,24(rsp)

mtlr r0

lwz r0,20(rsp)

mtcrf 0xff,r0

lwz r0,16(rsp)

mtxer r0

lwz r0,12(rsp)

mtctr r0

lwz r0,8(rsp)

addi rsp,rsp,80

rfi

.endm

gInterruptVectorTable:

Have a great day,
Yiping

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Re: Which registers should I save when saving state in timer interupt handler on mpc8306?

maojiu — Tue, 19 Aug 2014 13:40:32 GMT

Hello Yiping Wang:

I appreciate your help. However, when I use the statement “stwu rsp, -80(rsp)”, an error comes out and the error message is :” unsupported relocation against rsp”.

I am a fresh man in embedded world and mpc8306 is my first chip to work on, would you please recommend some materials about porting on mpc8306?

Moreover, I have a stupid question: Since I think the statement “stwu rsp, -80(rsp)” is writing the content in “rsp” (assume it is “ A”) to the address “A-80” and set “rsp” to “A-80”, what will happen if there is already some important data in the address “A-80” , can it be safely overwrote especially when saving state for task switching?

Re: Which registers should I save when saving state in timer interupt handler on mpc8306?

scottwood — Tue, 19 Aug 2014 19:51:45 GMT

The CodeWarrior code appears to be depending on "#define rsp r1" in some header. It also appears to be written for a simple kernel-only environment that doesn't need to switch stacks on exception entry. Be wary of code samples given without context.

Re: Which registers should I save when saving state in timer interupt handler on mpc8306?

yipingwang — Thu, 21 Aug 2014 07:45:37 GMT

Hello Mao Jiu,

The variable rsp is stack frame pointer, it is R1 Register in CodeWarrior EABI Specification.

The above Code comes from CodeWarrior MPC8306 bareboard project(without OS).

Have a great day,
Yiping

Re: Which registers should I save when saving state in timer interupt handler on mpc8306?

maojiu — Thu, 21 Aug 2014 08:43:30 GMT

Hello Yiping:

Thank you for your reply.

I have an OS, freeRTOS, but I have trouble in switching tasks. Since I haven’t figured out whether the assembly code for task switching in timer interrupt handler is wrong or not, I’m now checking the C++ code in freeRTOS related to task switching again. However, I think the C++ code couldn’t be wrong, since I have read it for several times and I’m familiar with C++. Thus, as a fresh man in embedded world, I hope you can give me some advices for getting start on mpc8306. Any help will be appreciated.

Have a nice day,

Xue Liu