diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/IRQ-domain.txt | 117 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/arm/vexpress.txt | 146 |
2 files changed, 263 insertions, 0 deletions
diff --git a/Documentation/IRQ-domain.txt b/Documentation/IRQ-domain.txt new file mode 100644 index 0000000..27dcaab --- /dev/null +++ b/Documentation/IRQ-domain.txt @@ -0,0 +1,117 @@ +irq_domain interrupt number mapping library + +The current design of the Linux kernel uses a single large number +space where each separate IRQ source is assigned a different number. +This is simple when there is only one interrupt controller, but in +systems with multiple interrupt controllers the kernel must ensure +that each one gets assigned non-overlapping allocations of Linux +IRQ numbers. + +The irq_alloc_desc*() and irq_free_desc*() APIs provide allocation of +irq numbers, but they don't provide any support for reverse mapping of +the controller-local IRQ (hwirq) number into the Linux IRQ number +space. + +The irq_domain library adds mapping between hwirq and IRQ numbers on +top of the irq_alloc_desc*() API. An irq_domain to manage mapping is +preferred over interrupt controller drivers open coding their own +reverse mapping scheme. + +irq_domain also implements translation from Device Tree interrupt +specifiers to hwirq numbers, and can be easily extended to support +other IRQ topology data sources. + +=== irq_domain usage === +An interrupt controller driver creates and registers an irq_domain by +calling one of the irq_domain_add_*() functions (each mapping method +has a different allocator function, more on that later). The function +will return a pointer to the irq_domain on success. The caller must +provide the allocator function with an irq_domain_ops structure with +the .map callback populated as a minimum. + +In most cases, the irq_domain will begin empty without any mappings +between hwirq and IRQ numbers. Mappings are added to the irq_domain +by calling irq_create_mapping() which accepts the irq_domain and a +hwirq number as arguments. If a mapping for the hwirq doesn't already +exist then it will allocate a new Linux irq_desc, associate it with +the hwirq, and call the .map() callback so the driver can perform any +required hardware setup. + +When an interrupt is received, irq_find_mapping() function should +be used to find the Linux IRQ number from the hwirq number. + +If the driver has the Linux IRQ number or the irq_data pointer, and +needs to know the associated hwirq number (such as in the irq_chip +callbacks) then it can be directly obtained from irq_data->hwirq. + +=== Types of irq_domain mappings === +There are several mechanisms available for reverse mapping from hwirq +to Linux irq, and each mechanism uses a different allocation function. +Which reverse map type should be used depends on the use case. Each +of the reverse map types are described below: + +==== Linear ==== +irq_domain_add_linear() + +The linear reverse map maintains a fixed size table indexed by the +hwirq number. When a hwirq is mapped, an irq_desc is allocated for +the hwirq, and the IRQ number is stored in the table. + +The Linear map is a good choice when the maximum number of hwirqs is +fixed and a relatively small number (~ < 256). The advantages of this +map are fixed time lookup for IRQ numbers, and irq_descs are only +allocated for in-use IRQs. The disadvantage is that the table must be +as large as the largest possible hwirq number. + +The majority of drivers should use the linear map. + +==== Tree ==== +irq_domain_add_tree() + +The irq_domain maintains a radix tree map from hwirq numbers to Linux +IRQs. When an hwirq is mapped, an irq_desc is allocated and the +hwirq is used as the lookup key for the radix tree. + +The tree map is a good choice if the hwirq number can be very large +since it doesn't need to allocate a table as large as the largest +hwirq number. The disadvantage is that hwirq to IRQ number lookup is +dependent on how many entries are in the table. + +Very few drivers should need this mapping. At the moment, powerpc +iseries is the only user. + +==== No Map ===- +irq_domain_add_nomap() + +The No Map mapping is to be used when the hwirq number is +programmable in the hardware. In this case it is best to program the +Linux IRQ number into the hardware itself so that no mapping is +required. Calling irq_create_direct_mapping() will allocate a Linux +IRQ number and call the .map() callback so that driver can program the +Linux IRQ number into the hardware. + +Most drivers cannot use this mapping. + +==== Legacy ==== +irq_domain_add_legacy() +irq_domain_add_legacy_isa() + +The Legacy mapping is a special case for drivers that already have a +range of irq_descs allocated for the hwirqs. It is used when the +driver cannot be immediately converted to use the linear mapping. For +example, many embedded system board support files use a set of #defines +for IRQ numbers that are passed to struct device registrations. In that +case the Linux IRQ numbers cannot be dynamically assigned and the legacy +mapping should be used. + +The legacy map assumes a contiguous range of IRQ numbers has already +been allocated for the controller and that the IRQ number can be +calculated by adding a fixed offset to the hwirq number, and +visa-versa. The disadvantage is that it requires the interrupt +controller to manage IRQ allocations and it requires an irq_desc to be +allocated for every hwirq, even if it is unused. + +The legacy map should only be used if fixed IRQ mappings must be +supported. For example, ISA controllers would use the legacy map for +mapping Linux IRQs 0-15 so that existing ISA drivers get the correct IRQ +numbers. diff --git a/Documentation/devicetree/bindings/arm/vexpress.txt b/Documentation/devicetree/bindings/arm/vexpress.txt new file mode 100644 index 0000000..ec8b50c --- /dev/null +++ b/Documentation/devicetree/bindings/arm/vexpress.txt @@ -0,0 +1,146 @@ +ARM Versatile Express boards family +----------------------------------- + +ARM's Versatile Express platform consists of a motherboard and one +or more daughterboards (tiles). The motherboard provides a set of +peripherals. Processor and RAM "live" on the tiles. + +The motherboard and each core tile should be described by a separate +Device Tree source file, with the tile's description including +the motherboard file using a /include/ directive. As the motherboard +can be initialized in one of two different configurations ("memory +maps"), care must be taken to include the correct one. + +Required properties in the root node: +- compatible value: + compatible = "arm,vexpress,<model>", "arm,vexpress"; + where <model> is the full tile model name (as used in the tile's + Technical Reference Manual), eg.: + - for Coretile Express A5x2 (V2P-CA5s): + compatible = "arm,vexpress,v2p-ca5s", "arm,vexpress"; + - for Coretile Express A9x4 (V2P-CA9): + compatible = "arm,vexpress,v2p-ca9", "arm,vexpress"; + If a tile comes in several variants or can be used in more then one + configuration, the compatible value should be: + compatible = "arm,vexpress,<model>,<variant>", \ + "arm,vexpress,<model>", "arm,vexpress"; + eg: + - Coretile Express A15x2 (V2P-CA15) with Tech Chip 1: + compatible = "arm,vexpress,v2p-ca15,tc1", \ + "arm,vexpress,v2p-ca15", "arm,vexpress"; + - LogicTile Express 13MG (V2F-2XV6) running Cortex-A7 (3 cores) SMM: + compatible = "arm,vexpress,v2f-2xv6,ca7x3", \ + "arm,vexpress,v2f-2xv6", "arm,vexpress"; + +Optional properties in the root node: +- tile model name (use name from the tile's Technical Reference + Manual, eg. "V2P-CA5s") + model = "<model>"; +- tile's HBI number (unique ARM's board model ID, visible on the + PCB's silkscreen) in hexadecimal transcription: + arm,hbi = <0xhbi> + eg: + - for Coretile Express A5x2 (V2P-CA5s) HBI-0191: + arm,hbi = <0x191>; + - Coretile Express A9x4 (V2P-CA9) HBI-0225: + arm,hbi = <0x225>; + +Top-level standard "cpus" node is required. It must contain a node +with device_type = "cpu" property for every available core, eg.: + + cpus { + #address-cells = <1>; + #size-cells = <0>; + + cpu@0 { + device_type = "cpu"; + compatible = "arm,cortex-a5"; + reg = <0>; + }; + }; + +The motherboard description file provides a single "motherboard" node +using 2 address cells corresponding to the Static Memory Bus used +between the motherboard and the tile. The first cell defines the Chip +Select (CS) line number, the second cell address offset within the CS. +All interrupt lines between the motherboard and the tile are active +high and are described using single cell. + +Optional properties of the "motherboard" node: +- motherboard's memory map variant: + arm,v2m-memory-map = "<name>"; + where name is one of: + - "rs1" - for RS1 map (i.a. peripherals on CS3); this map is also + referred to as "ARM Cortex-A Series memory map": + arm,v2m-memory-map = "rs1"; + When this property is missing, the motherboard is using the original + memory map (also known as the "Legacy memory map", primarily used + with the original CoreTile Express A9x4) with peripherals on CS7. + +Motherboard .dtsi files provide a set of labelled peripherals that +can be used to obtain required phandle in the tile's "aliases" node: +- UARTs, note that the numbers correspond to the physical connectors + on the motherboard's back panel: + v2m_serial0, v2m_serial1, v2m_serial2 and v2m_serial3 +- I2C controllers: + v2m_i2c_dvi and v2m_i2c_pcie +- SP804 timers: + v2m_timer01 and v2m_timer23 + +Current Linux implementation requires a "arm,v2m_timer" alias +pointing at one of the motherboard's SP804 timers, if it is to be +used as the system timer. This alias should be defined in the +motherboard files. + +The tile description must define "ranges", "interrupt-map-mask" and +"interrupt-map" properties to translate the motherboard's address +and interrupt space into one used by the tile's processor. + +Abbreviated example: + +/dts-v1/; + +/ { + model = "V2P-CA5s"; + arm,hbi = <0x225>; + compatible = "arm,vexpress-v2p-ca5s", "arm,vexpress"; + interrupt-parent = <&gic>; + #address-cells = <1>; + #size-cells = <1>; + + chosen { }; + + aliases { + serial0 = &v2m_serial0; + }; + + cpus { + #address-cells = <1>; + #size-cells = <0>; + + cpu@0 { + device_type = "cpu"; + compatible = "arm,cortex-a5"; + reg = <0>; + }; + }; + + gic: interrupt-controller@2c001000 { + compatible = "arm,cortex-a9-gic"; + #interrupt-cells = <3>; + #address-cells = <0>; + interrupt-controller; + reg = <0x2c001000 0x1000>, + <0x2c000100 0x100>; + }; + + motherboard { + /* CS0 is visible at 0x08000000 */ + ranges = <0 0 0x08000000 0x04000000>; + interrupt-map-mask = <0 0 63>; + /* Active high IRQ 0 is connected to GIC's SPI0 */ + interrupt-map = <0 0 0 &gic 0 0 4>; + }; +}; + +/include/ "vexpress-v2m-rs1.dtsi" |
