Commit 7a7967dc authored by Philippe Gerum's avatar Philippe Gerum Committed by Mike Frysinger
Browse files

Blackfin: document __ipipe_call_irqtail


Signed-off-by: default avatarPhilippe Gerum <rpm@xenomai.org>
Signed-off-by: default avatarMike Frysinger <vapier@gentoo.org>
parent 70f47202
......@@ -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;
......
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