path: root/Documentation
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authorLinus Torvalds <torvalds@linux-foundation.org>2014-12-10 09:01:01 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-10 09:01:01 -0800
commit9e66645d72d3c395da92b0f8855c787f4b5f0e89 (patch)
tree61b94adb6c32340c45b6d984837556b6b845e983 /Documentation
parentMerge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip (diff)
parentgenirq: Move irq_chip_write_msi_msg() helper to core (diff)
Merge branch 'irq-irqdomain-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq domain updates from Thomas Gleixner: "The real interesting irq updates: - Support for hierarchical irq domains: For complex interrupt routing scenarios where more than one interrupt related chip is involved we had no proper representation in the generic interrupt infrastructure so far. That made people implement rather ugly constructs in their nested irq chip implementations. The main offenders are x86 and arm/gic. To distangle that mess we have now hierarchical irqdomains which seperate the various interrupt chips and connect them via the hierarchical domains. That keeps the domain specific details internal to the particular hierarchy level and removes the criss/cross referencing of chip internals. The resulting hierarchy for a complex x86 system will look like this: vector mapped: 74 msi-0 mapped: 2 dmar-ir-1 mapped: 69 ioapic-1 mapped: 4 ioapic-0 mapped: 20 pci-msi-2 mapped: 45 dmar-ir-0 mapped: 3 ioapic-2 mapped: 1 pci-msi-1 mapped: 2 htirq mapped: 0 Neither ioapic nor pci-msi know about the dmar interrupt remapping between themself and the vector domain. If interrupt remapping is disabled ioapic and pci-msi become direct childs of the vector domain. In hindsight we should have done that years ago, but in hindsight we always know better :) - Support for generic MSI interrupt domain handling We have more and more non PCI related MSI interrupts, so providing a generic infrastructure for this is better than having all affected architectures implementing their own private hacks. - Support for PCI-MSI interrupt domain handling, based on the generic MSI support. This part carries the pci/msi branch from Bjorn Helgaas pci tree to avoid a massive conflict. The PCI/MSI parts are acked by Bjorn. I have two more branches on top of this. The full conversion of x86 to hierarchical domains and a partial conversion of arm/gic" * 'irq-irqdomain-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (41 commits) genirq: Move irq_chip_write_msi_msg() helper to core PCI/MSI: Allow an msi_controller to be associated to an irq domain PCI/MSI: Provide mechanism to alloc/free MSI/MSIX interrupt from irqdomain PCI/MSI: Enhance core to support hierarchy irqdomain PCI/MSI: Move cached entry functions to irq core genirq: Provide default callbacks for msi_domain_ops genirq: Introduce msi_domain_alloc/free_irqs() asm-generic: Add msi.h genirq: Add generic msi irq domain support genirq: Introduce callback irq_chip.irq_write_msi_msg genirq: Work around __irq_set_handler vs stacked domains ordering issues irqdomain: Introduce helper function irq_domain_add_hierarchy() irqdomain: Implement a method to automatically call parent domains alloc/free genirq: Introduce helper irq_domain_set_info() to reduce duplicated code genirq: Split out flow handler typedefs into seperate header file genirq: Add IRQ_SET_MASK_OK_DONE to support stacked irqchip genirq: Introduce irq_chip.irq_compose_msi_msg() to support stacked irqchip genirq: Add more helper functions to support stacked irq_chip genirq: Introduce helper functions to support stacked irq_chip irqdomain: Do irq_find_mapping and set_type for hierarchy irqdomain in case OF ...
Diffstat (limited to 'Documentation')
1 files changed, 71 insertions, 0 deletions
diff --git a/Documentation/IRQ-domain.txt b/Documentation/IRQ-domain.txt
index 8a8b82c9ca53..39cfa72732ff 100644
--- a/Documentation/IRQ-domain.txt
+++ b/Documentation/IRQ-domain.txt
@@ -151,3 +151,74 @@ used and no descriptor gets allocated it is very important to make sure
that the driver using the simple domain call irq_create_mapping()
before any irq_find_mapping() since the latter will actually work
for the static IRQ assignment case.
+==== Hierarchy IRQ domain ====
+On some architectures, there may be multiple interrupt controllers
+involved in delivering an interrupt from the device to the target CPU.
+Let's look at a typical interrupt delivering path on x86 platforms:
+Device --> IOAPIC -> Interrupt remapping Controller -> Local APIC -> CPU
+There are three interrupt controllers involved:
+1) IOAPIC controller
+2) Interrupt remapping controller
+3) Local APIC controller
+To support such a hardware topology and make software architecture match
+hardware architecture, an irq_domain data structure is built for each
+interrupt controller and those irq_domains are organized into hierarchy.
+When building irq_domain hierarchy, the irq_domain near to the device is
+child and the irq_domain near to CPU is parent. So a hierarchy structure
+as below will be built for the example above.
+ CPU Vector irq_domain (root irq_domain to manage CPU vectors)
+ ^
+ |
+ Interrupt Remapping irq_domain (manage irq_remapping entries)
+ ^
+ |
+ IOAPIC irq_domain (manage IOAPIC delivery entries/pins)
+There are four major interfaces to use hierarchy irq_domain:
+1) irq_domain_alloc_irqs(): allocate IRQ descriptors and interrupt
+ controller related resources to deliver these interrupts.
+2) irq_domain_free_irqs(): free IRQ descriptors and interrupt controller
+ related resources associated with these interrupts.
+3) irq_domain_activate_irq(): activate interrupt controller hardware to
+ deliver the interrupt.
+3) irq_domain_deactivate_irq(): deactivate interrupt controller hardware
+ to stop delivering the interrupt.
+Following changes are needed to support hierarchy irq_domain.
+1) a new field 'parent' is added to struct irq_domain; it's used to
+ maintain irq_domain hierarchy information.
+2) a new field 'parent_data' is added to struct irq_data; it's used to
+ build hierarchy irq_data to match hierarchy irq_domains. The irq_data
+ is used to store irq_domain pointer and hardware irq number.
+3) new callbacks are added to struct irq_domain_ops to support hierarchy
+ irq_domain operations.
+With support of hierarchy irq_domain and hierarchy irq_data ready, an
+irq_domain structure is built for each interrupt controller, and an
+irq_data structure is allocated for each irq_domain associated with an
+IRQ. Now we could go one step further to support stacked(hierarchy)
+irq_chip. That is, an irq_chip is associated with each irq_data along
+the hierarchy. A child irq_chip may implement a required action by
+itself or by cooperating with its parent irq_chip.
+With stacked irq_chip, interrupt controller driver only needs to deal
+with the hardware managed by itself and may ask for services from its
+parent irq_chip when needed. So we could achieve a much cleaner
+software architecture.
+For an interrupt controller driver to support hierarchy irq_domain, it
+needs to:
+1) Implement irq_domain_ops.alloc and irq_domain_ops.free
+2) Optionally implement irq_domain_ops.activate and
+ irq_domain_ops.deactivate.
+3) Optionally implement an irq_chip to manage the interrupt controller
+ hardware.
+4) No need to implement irq_domain_ops.map and irq_domain_ops.unmap,
+ they are unused with hierarchy irq_domain.
+Hierarchy irq_domain may also be used to support other architectures,
+such as ARM, ARM64 etc.