ARC: SMP support
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>
diff --git a/arch/arc/kernel/ctx_sw.c b/arch/arc/kernel/ctx_sw.c
index fbf739c..60844da 100644
--- a/arch/arc/kernel/ctx_sw.c
+++ b/arch/arc/kernel/ctx_sw.c
@@ -58,7 +58,18 @@
* For SMP extra work to get to &_current_task[cpu]
* (open coded SET_CURR_TASK_ON_CPU)
*/
+#ifndef CONFIG_SMP
"st %2, [@_current_task] \n\t"
+#else
+ "lr r24, [identity] \n\t"
+ "lsr r24, r24, 8 \n\t"
+ "bmsk r24, r24, 7 \n\t"
+ "add2 r24, @_current_task, r24 \n\t"
+ "st %2, [r24] \n\t"
+#endif
+#ifdef CONFIG_ARC_CURR_IN_REG
+ "mov r25, %2 \n\t"
+#endif
/* get ksp of incoming task from tsk->thread.ksp */
"ld.as sp, [%2, %1] \n\t"