Hi, On 07/06/2016 11:30 AM, Thomas Gleixner wrote: > On Wed, 6 Jul 2016, Marc Zyngier wrote: >> On 05/07/16 20:24, Thomas Gleixner wrote: >>> On Tue, 5 Jul 2016, Marc Zyngier wrote: >>>> Hardcoded? No way. You simply implement a route allocator in your >>>> driver, assigning them as needed. And yes, if you have more than 24 >>>> interrupts, they get muxed. >>> >>> There is one caveat though. Under some circumstances (think RT) you want to >>> configure which interrupts get muxed and which not. We really should have >>> that >>> option, but yes for anything which has less than 24 autorouting is the way >>> to >>> go. >> >> Good point. I can see two possibilities for that: >> >> - either we describe this DT with some form of hint, indicating what are >> the inputs that can be muxed to a single output. Easy, but the DT guys >> are going to throw rocks at me for being Linux-specific. > > That's not necessarily Linux specific. The problem arises with any other OS as > well. > >> - or we have a way to express QoS in the irq subsystem, and a driver can >> request an interrupt with a "make it fast" flag. Of course, everybody >> and his dog are going to ask for it, and we're back to square one. > > That and the driver does not know about the particular application > scenario/system configuration. > >> Do we have a way to detect which interrupt is more likely to be >> sensitive to muxing? My hunch is that if it is requested with >> IRQF_SHARED, then it is effectively muxable. Thoughts? > > That's too late. request_irq happens _after_ the interrupt is set up and the > routing established. >
What about using 3 values for the interrupt description like the GIC does? When connecting to the GIC we say "interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;" If devices using this driver (the one from the RFC) requested the interrupt like: "interrupts = <0 38 IRQ_TYPE_LEVEL_HIGH>;" "interrupts = <2 27 IRQ_TYPE_LEVEL_HIGH>;" etc. with the first field being the "group", then the driver could create a domain for the device's IRQ (or associate it to an existing one if it has already been created). It would thus serve as a hint on how to create domains and how to share IRQs into the same line (domain). I guess I can get such information from the .translate and .alloc callbacks from a newly created domain hierarchy attached to the GIC, right? What do you think? Best regards, Sebastian
