On 2015/10/15 23:39, Marc Zyngier wrote: > There seems to be a new class of interrupt controller out there whose > sole purpose (apart from making everybody's life a nightmare) is to > turn wired interrupts into MSIs. > > Instead of considering that the MSIs allocated to a device are for the > direct use of that device, we can turn this set of MSIs into a irq > domain, and use that domain to build a standard irqchip on top of > that. Hi Marc, There's a working to enable Intel VMD storage device, which has the similar requirement. Basically a PCIe hierarchy is hidden behind a parent PCIe device, so we need to use the PCIe irqs on parent to de-multiple PCIe IRQs from hidden PCIe devices. Seems a chance for consolidation here. cc Keith Busch <keith.busch@xxxxxxxxx> who is the author of VMD device driver. Thanks! Gerry > > This requires some (slightly ugly) surgery in both the generic MSI and > platform MSI layers, but the amount of code is actually relatively > small (about +150 LoC so far). > > On top of that, we add a dummy driver for a such a bridge, hoping that > this will give enough information to driver authors so that they can > use this new feature. An even more stupid client driver is provided to > show the interrupt stack allocation: > > dummydev dummy-dev: Probing > dummydev dummy-dev: Allocated IRQ35 > dummydev dummy-dev: Probing OK > dummydev dummy-dev: IRQ35 hwirq 5 domain msichip_domain_ops > dummydev dummy-dev: IRQ35 hwirq 0 domain msi_domain_ops > dummydev dummy-dev: IRQ35 hwirq 8192 domain its_domain_ops > dummydev dummy-dev: IRQ35 hwirq 8192 domain gic_irq_domain_ops > > While this seems to work, it is far from being perfect: > > - This is a prototype: error handling is rubbish, and there could be > better abstractions to use. > > - It relies on not declaring this bridge with IRQCHIP_DECLARE in order > to prevent the DT layer from allocating interrupts behind our back. > > - There is some probe ordering issues between the bridge and the wired > interrupt device, leading to the use of -EPROBE_DEFER. > > The last two points could be addressed directly in the OF layer, as > this is a generic device ordering issue (and people are already > working on that). > > I'd welcome any comment on that approach (though I'm going to make > myself scarse over the next two weeks). > > Marc Zyngier (7): > platform-msi: Allow MSIs to be allocated in chunks > platform-msi: Factor out allocation/free of private data > irqdomain: Make irq_domain_alloc_irqs_recursive available > genirq/msi: Make the .prepare callback reusable > genirq/msi: Add msi_domain_populate_irqs > platform-msi: Allow creation of a MSI-based stacked irq domain > irqchip: [Example] dummy wired interrupt/MSI bridge driver > > drivers/base/platform-msi.c | 185 ++++++++++++++++++++-------- > drivers/irqchip/Kconfig | 7 ++ > drivers/irqchip/Makefile | 1 + > drivers/irqchip/irq-msichip.c | 271 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/irqdomain.h | 3 + > include/linux/msi.h | 16 +++ > kernel/irq/irqdomain.c | 6 +- > kernel/irq/msi.c | 47 +++++++- > 8 files changed, 481 insertions(+), 55 deletions(-) > create mode 100644 drivers/irqchip/irq-msichip.c > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
