41195d236e
ARC common code to enable a SMP system + ISS provided SMP extensions. ARC700 natively lacks SMP support, hence some of the core features are are only enabled if SoCs have the necessary h/w pixie-dust. This includes: -Inter Processor Interrupts (IPI) -Cache coherency -load-locked/store-conditional ... The low level exception handling would be completely broken in SMP because we don't have hardware assisted stack switching. Thus a fair bit of this code is repurposing the MMU_SCRATCH reg for event handler prologues to keep them re-entrant. Many thanks to Rajeshwar Ranga for his initial "major" contributions to SMP Port (back in 2008), and to Noam Camus and Gilad Ben-Yossef for help with resurrecting that in 3.2 kernel (2012). Note that this platform code is again singleton design pattern - so multiple SMP platforms won't build at the moment - this deficiency is addressed in subsequent patches within this series. Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Rajeshwar Ranga <rajeshwar.ranga@gmail.com> Cc: Noam Camus <noamc@ezchip.com> Cc: Gilad Ben-Yossef <gilad@benyossef.com>
109 lines
3.2 KiB
C
109 lines
3.2 KiB
C
/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Vineetg: Aug 2009
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* -"C" version of lowest level context switch asm macro called by schedular
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* gcc doesn't generate the dward CFI info for hand written asm, hence can't
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* backtrace out of it (e.g. tasks sleeping in kernel).
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* So we cheat a bit by writing almost similar code in inline-asm.
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* -This is a hacky way of doing things, but there is no other simple way.
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* I don't want/intend to extend unwinding code to understand raw asm
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*/
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#include <asm/asm-offsets.h>
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#include <linux/sched.h>
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struct task_struct *__sched
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__switch_to(struct task_struct *prev_task, struct task_struct *next_task)
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{
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unsigned int tmp;
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unsigned int prev = (unsigned int)prev_task;
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unsigned int next = (unsigned int)next_task;
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int num_words_to_skip = 1;
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#ifdef CONFIG_ARC_CURR_IN_REG
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num_words_to_skip++;
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#endif
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__asm__ __volatile__(
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/* FP/BLINK save generated by gcc (standard function prologue */
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"st.a r13, [sp, -4] \n\t"
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"st.a r14, [sp, -4] \n\t"
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"st.a r15, [sp, -4] \n\t"
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"st.a r16, [sp, -4] \n\t"
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"st.a r17, [sp, -4] \n\t"
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"st.a r18, [sp, -4] \n\t"
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"st.a r19, [sp, -4] \n\t"
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"st.a r20, [sp, -4] \n\t"
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"st.a r21, [sp, -4] \n\t"
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"st.a r22, [sp, -4] \n\t"
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"st.a r23, [sp, -4] \n\t"
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"st.a r24, [sp, -4] \n\t"
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#ifndef CONFIG_ARC_CURR_IN_REG
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"st.a r25, [sp, -4] \n\t"
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#endif
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"sub sp, sp, %4 \n\t" /* create gutter at top */
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/* set ksp of outgoing task in tsk->thread.ksp */
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"st.as sp, [%3, %1] \n\t"
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"sync \n\t"
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/*
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* setup _current_task with incoming tsk.
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* optionally, set r25 to that as well
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* For SMP extra work to get to &_current_task[cpu]
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* (open coded SET_CURR_TASK_ON_CPU)
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*/
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#ifndef CONFIG_SMP
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"st %2, [@_current_task] \n\t"
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#else
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"lr r24, [identity] \n\t"
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"lsr r24, r24, 8 \n\t"
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"bmsk r24, r24, 7 \n\t"
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"add2 r24, @_current_task, r24 \n\t"
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"st %2, [r24] \n\t"
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#endif
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#ifdef CONFIG_ARC_CURR_IN_REG
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"mov r25, %2 \n\t"
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#endif
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/* get ksp of incoming task from tsk->thread.ksp */
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"ld.as sp, [%2, %1] \n\t"
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/* start loading it's CALLEE reg file */
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"add sp, sp, %4 \n\t" /* skip gutter at top */
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#ifndef CONFIG_ARC_CURR_IN_REG
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"ld.ab r25, [sp, 4] \n\t"
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#endif
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"ld.ab r24, [sp, 4] \n\t"
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"ld.ab r23, [sp, 4] \n\t"
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"ld.ab r22, [sp, 4] \n\t"
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"ld.ab r21, [sp, 4] \n\t"
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"ld.ab r20, [sp, 4] \n\t"
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"ld.ab r19, [sp, 4] \n\t"
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"ld.ab r18, [sp, 4] \n\t"
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"ld.ab r17, [sp, 4] \n\t"
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"ld.ab r16, [sp, 4] \n\t"
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"ld.ab r15, [sp, 4] \n\t"
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"ld.ab r14, [sp, 4] \n\t"
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"ld.ab r13, [sp, 4] \n\t"
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/* last (ret value) = prev : although for ARC it mov r0, r0 */
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"mov %0, %3 \n\t"
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/* FP/BLINK restore generated by gcc (standard func epilogue */
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: "=r"(tmp)
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: "n"((TASK_THREAD + THREAD_KSP) / 4), "r"(next), "r"(prev),
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"n"(num_words_to_skip * 4)
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: "blink"
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);
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return (struct task_struct *)tmp;
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}
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