SMP on Xilinx Zynq

[Joel Sherrill]

On February 28, 2015 12:38:54 PM CST, "Maldonado, Sergio E." <smaldona at slac.stanford.edu> wrote:
>Hello,
>
>Attempting to get SMP working on my Xilinx Zynq platform.  
>I'm currently running RTEMS compiled from the head of the git repo
>master branch (as of 2/28/15), so I should have the latest updates.
>
>The problem I have is that multitasking does not work when both cores
>are enabled.
>
>I'm looking for some input on what could be going wrong and how to fix
>it.
>
>Scenario:
>
>At system boot, I can verify that core 0 completes RTEMS boot_card
>initialization, and starts multitasking.
>However, Core 0 does _not_ execute the Init task entry point and
>instead goes straight to its idle loop.
>
>Meanwhile, Core 1 starts and executes until it reaches the first
>_CPU_Context_Switch/_CPU_Context_Restore call.
>If I step into Core 1, I can see that it never returns from this
>routine and stays in an infinite loop of the following instructions

Did you configure multiple cores? There are SMP specific configuration parameters such as number of cores in the system.

>
>83		bne	.L_check_thread_dispatch_necessary
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:131
>131		GET_SELF_CPU_CONTROL	r2, r3
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:134
>134		ldrb	r4, [r2, #PER_CPU_DISPATCH_NEEDED]
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:135
>135		cmp	r4, #0
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:136
>136		beq	.L_check_is_executing
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:80
>80		add	r3, r1, #ARM_CONTEXT_CONTROL_IS_EXECUTING_OFFSET
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:81
>81		ldrexb	r4, [r3]
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:82
>82		cmp	r4, #0
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:83
>83		bne	.L_check_thread_dispatch_necessary
>(gdb) s
>?? ()
>at
>../../../../../../../../src/c/src/../../cpukit/score/cpu/arm/cpu_asm.S:131
>131		GET_SELF_CPU_CONTROL	r2, r3
>(gdb) s
>...
>
>
>Consequently, the Init task entry point is never executed by either
>core, and the system does not complete startup.
>
>Any thoughts on why Core 1 will not complete its transition to
>multitasking?
>
>Here's a piece of information that might be useful:
>
>When I configure RTEMS SMP with just 1 processor, the system
>successfully starts multitasking and the Init task entry point _does_
>get executed by Core 0.
>
>Thank you,
>
>Sergio Maldonado - SLAC
>
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--joel