On Thursday 15 August 2013 04:51 PM, Linus Walleij wrote: > On Thu, Aug 15, 2013 at 10:26 PM, Santosh Shilimkar > <santosh.shilimkar@xxxxxx> wrote: >> On Thursday 15 August 2013 04:01 PM, Linus Walleij wrote: >>> On Tue, Aug 13, 2013 at 11:56 AM, Sricharan R <r.sricharan@xxxxxx> wrote: >>> >>>> Initially irqchip was discussed, but we also have a DMA crossbar >>>> to map the dma-requests. Since both irq/dma crossbars should be handled, >>>> pinctrl was suggested as the appropriate place to handle this. >>> >>> I think it is better to use irqchip. >>> >> Did you happen to read the thread why irqchip is in-appropriate >> for such an IP. > > 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 > It was discussed in couple of threads but the main point was the need of a link needed for the irqchip. >> As I said earlier, an IRQ-chip always need a >> real IRQ link (even for the chained one) to the primary irqchip. >> >> This IP is just dummy IP makes the connections for the primary >> irqchip(read GIC). And its use only limited to make the >> connection between the peripheral IRQ event to the GIC IRQ line. >> >> 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. >>> I don't see any way to really abstract this pretty simple crossbar >>> for reuse across subsystems. >>> >> This exactly the reason, i am against idea of over-engineering the >> simple IP whose only job is to make the physical wire connection >> in software where as this is generally done in RTL by default on >> most of the SOCs. > > Well, it was made accessible by software, and if someone has a > usecase that requires this do be done dynamically, i.e. not just > being set up by firmware and never touched, and that use case > is valid, then I guess we need to do something... > > I think it was mentioned in the thread that there is really such > a usecase? > Actually there is no practical usecase but one but one can manufacture it ;-) -- 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
