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

[maojiu]

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 !

[yipingwang]

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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[maojiu]

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? 

[yipingwang]

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

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[maojiu]

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

[scottwood]

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.