On 12/01/16 09:12, Vineet Gupta wrote: [...] >> HANDLE_DOMAIN_IRQ is not mandatory at all - a number of architectures >> had something open-coded in the past (with some drawbacks and/or bugs), >> and this config option is just one of the ways to get it right. >> >> MIPS/PPC perform the reverse lookup directly, without using this >> infrastructure, and that would be a valid approach for ARC too. > > I'd rather use the generic infrastructure and improve it if needed ! > >>>> Marc, I hope you are back from holidays. When u get a chance could you please >>>> respond to above. >>>> >>>> Also I tool a stab at it anyways. >>>> 1. Enabled HANDLE_DOMAIN_IRQ >>>> 2. arch_do_IRQ() calls handle_domain_irq(NULL, hwirq, regs) since that code >>>> doesn't know about domains. >>>> >>>> It fails w/o irq_set_default_host() being called. >> Well, that's expected. unless you use the underlying primitive >> (__handle_domain_irq) and pass false as the parameter for lookup (see >> handle_IRQ() in arch/arm/kernel/irq.c). This is what we use for "legacy" >> platforms that do not support domains. > > Right I saw that and that causes virq = hwirq - kind of defeats the purpose if we > were doing this on ARC. You can forget about this if you convert all your platforms to using domains. But if you have to deal with a transition period (which, in the ARM case, will last exactly forever because some platforms will never be converted to DT), this comes in handy. >> >>>> If we go back to sunxi example you quoted above, it relies on driver passing the >>>> domain to handle_domain_irq(). IMHO it is simpler if we had the default domain. >>>> >>>> So long story short, ARC can be made to use handle_domain_irq() w/o the song and >>>> dance of registering another callback from irqchip code if we retained the default >>>> domain setting. >> This only works if you can guarantee that you will never have another >> irqchip calling irq_set_default_host()... If your system is always >> simple enough to guarantee that, why not. > > ATM we can certainly assume that. > > However with ARM approach two irqchips can still call set_handle_irq() and only > the first one succeeds (and others return silently). That seems wrong to me - > irq_xxx.c will still use the handler registered by say irq_sun41.c ? Oh, this is by no mean foolproof. We do rely on irqchips installing their primary handler only if they are truly the primary irqchip (they do not have a parent). Anything else will fail badly. So if you're confident that you can ensure that noone will set de default domain twice, you'll be fine. Thanks, M. -- Jazz is not dead. It just smells funny...
