Hi Linus, On Thursday 22 August 2013 02:40 AM, Linus Walleij wrote: > On Thu, Aug 15, 2013 at 11:14 PM, Santosh Shilimkar > <santosh.shilimkar@xxxxxx> wrote: >> On Thursday 15 August 2013 04:51 PM, Linus Walleij wrote: > (...) >>> Sorry I don't understand what thread that is... can you point me there? >>> My previous statement on this issue what this: >>> http://marc.info/?l=linux-kernel&m=137442541628641&w=2 > (...) >>>> I don't see how you can make this happen with an irqchip >>>> infrastructure. >>> I think my post above describes this. >>> >> Sorry for being dumb but I don't think cascaded irqchip examples >> like GPIO and cross-bars are same. If you take an example of >> GPIO irqchip, it always have a physical connection even if it >> is 1 IRQ line for (32 logical/sparse IRQs). That goes with >> other MFD examples too. >> >> So may be I am still missing something in your proposal. > Why does it matter if it is a GPIO or MFD or whatever? > The point is that the IRQ line passes thru something else, > and this we model as an irqdomain. > > Anyway here is a silicon cascaded IRQ chip: > arch/arm/mach-versatile/core.c > See versatile_init_irq(): > > __vic_init(VA_VIC_BASE, IRQ_VIC_START, ~0, 0, np); > (...) > fpga_irq_init(VA_SIC_BASE, "SIC", IRQ_SIC_START, > IRQ_VICSOURCE31, PIC_VALID, np); > > The VIC in the versatile has the SIC cascaded from one of > its IRQ lines. Both the VIC and SIC (fpga IRQ) are > using irqdomains so the SIC spawns a child irqdomain > from IRQ 31 (last IRQ) of the VIC. Ok, this is a typical example of irqchip cascaded. > The difference with a crossbar is that it can software-config > which IRQ goes where, and does not have a callback > to clear interrupts or anything like that, it just passes them > thru. But it is best modeled as an irqdomain IMO. We can model crossbar as irqchip and gic as its interrupt parent and peripherals to have crossbar as interrupt-parent. peripherals will do request_irq(crossbar_number) | | crossbar_unmask() | | maps crossbar number<-> to interrupt number and calls request_irq(int_no, crossbar_handler,..) crossbar_handler(interrupt number) | | get crossbar number from interrupt number | | handle_irq(crossbar_domain(crossbar number)) So this means a extra dummy handler. Also the concern is by modelling it as irqchip, we will have to find a different solution for DMA crossbar. Regards, Sricharan -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
