diff options
| -rw-r--r-- | arch/blackfin/mach-common/interrupt.S | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/arch/blackfin/mach-common/interrupt.S b/arch/blackfin/mach-common/interrupt.S index 29fbf67..c754ff7 100644 --- a/arch/blackfin/mach-common/interrupt.S +++ b/arch/blackfin/mach-common/interrupt.S @@ -261,6 +261,31 @@ ENTRY(_evt_system_call) ENDPROC(_evt_system_call) #ifdef CONFIG_IPIPE +/* + * __ipipe_call_irqtail: lowers the current priority level to EVT15 + * before running a user-defined routine, then raises the priority + * level to EVT14 to prepare the caller for a normal interrupt + * return through RTI. + * + * We currently use this facility in two occasions: + * + * - to branch to __ipipe_irq_tail_hook as requested by a high + * priority domain after the pipeline delivered an interrupt, + * e.g. such as Xenomai, in order to start its rescheduling + * procedure, since we may not switch tasks when IRQ levels are + * nested on the Blackfin, so we have to fake an interrupt return + * so that we may reschedule immediately. + * + * - to branch to sync_root_irqs, in order to play any interrupt + * pending for the root domain (i.e. the Linux kernel). This lowers + * the core priority level enough so that Linux IRQ handlers may + * never delay interrupts handled by high priority domains; we defer + * those handlers until this point instead. This is a substitute + * to using a threaded interrupt model for the Linux kernel. + * + * r0: address of user-defined routine + * context: caller must have preempted EVT15, hw interrupts must be off. + */ ENTRY(___ipipe_call_irqtail) p0 = r0; r0.l = 1f; |
