Jan Kiszka wrote:
Anders Blomdell wrote:
While looking into how to implement sharing of interrupts between
realtime and non-realtime domains (and applying Wolfgang Grandegger's
which is necessary to make XN_ISR_ENABLE work at all on the PowerPC
platform), I'm beginning to think that XN_ISR_CHAINED and XN_ISR_ENABLE
are mutually exclusive, since if both are set, desc->handler->end will
be called twice:
1. When the realtime isr handler returns
2. When the Linux domain calls it in __do_IRQ
Yes, those bits are semantically exclusive. Actually, I think passing
both bits could even cause deadlocks if the RT-IRQ is raised again
before the non-RT handler got a chance to clear the IRQ source in hardware.
My impression as well, but it's nowhere documented, nor enforced in the code.
In the solution I have in mind at the moment, I will:
1. Add an extra iend handler argument to xnintr_init
2. If XN_ISR_ENABLE is returned from the isr handler,
replace desc->handler->end with the user supplied
Hereby I hope to be able to handle interrupts shared between realtime
and non-realtime domain, without having the realtime domain wait for all
non-realtime interrupts to finish. This is the scenario I'm thinking of:
1. A non-RT interrupt occurs
2. The (RT) isr handler detects the non-RT interrupt,
disables further non-RT interrupts on that irq-vector, replaces
This remains vague to me. How precisely will you disable? I guess at
hardware level, i.e. in a (non-RT) device-specific way: switch off the
bit in some hardware register that says "this device can produce IRQs",
If the non-RT driver sets that bit in its ISR routine, yes. I have the (overly
optimistic?) view that the non-RT ISR only does whatever is necessary to clear
the interrupt and leaves the enable/disable bits untouched.
desc->handler->end with the user supplied iend handler,
returns XN_ISR_CHAINED | XN_ISR_ENABLE.
3. RT interrupts are serviced by the (RT) isr handler,
4. The Linux domain get a chance to run the chained interrupt,
and eventually calls desc->handler->end (supplied iend handler)
5. The iend handler reenables non-RT interrupts.
Then this would switch on that bit again? Note that this may require to
synchronise the hardware access with parts of the non-RT driver.
Meanwhile I recalled that my hack to realise IRQ sharing between a RT
device and a non-RT eepro100 is filed on a public archive:
Thanks, I'll take a look at it.
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