Anders Blomdell wrote: > While looking into how to implement sharing of interrupts between > realtime and non-realtime domains (and applying Wolfgang Grandegger's > patch [https://mail.gna.org/public/xenomai-core/2006-01/msg00233.html], > 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. > > 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 > iend handler. > > 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", right? > 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, > returns XN_ISR_ENABLE > 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: https://mail.gna.org/public/xenomai-core/2005-11/msg00012.html > > Comments on the above are most welcome! > Jan
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