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linux/Documentation/devicetree/bindings/c6x/emifa.txt

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C6X: devicetree support This is the basic devicetree support for C6X. Currently, four boards are supported. Each one uses a different SoC part. Two of the four supported SoCs are multicore. One with 3 cores and the other with 6 cores. There is no coherency between the core-level caches, so SMP is not an option. It is possible to run separate kernel instances on the various cores. There is currently no C6X bootloader support for device trees so we build in the DTB for now. There are some interesting twists to the hardware which are of note for device tree support. Each core has its own interrupt controller which is controlled by special purpose core registers. This core controller provides 12 general purpose prioritized interrupt sources. Each core is contained within a hardware "module" which provides L1 and L2 caches, power control, and another interrupt controller which cascades into the core interrupt controller. These core module functions are controlled by memory mapped registers. The addresses for these registers are the same for each core. That is, when coreN accesses a module-level MMIO register at a given address, it accesses the register for coreN even though other cores would use the same address to access the register in the module containing those cores. Other hardware modules (timers, enet, etc) which are memory mapped can be accessed by all cores. The timers need some further explanation for multicore SoCs. Even though all timer control registers are visible to all cores, interrupt routing or other considerations may make a given timer more suitable for use by a core than some other timer. Because of this and the desire to have the same image run on more than one core, the timer nodes have a "ti,core-mask" property which is used by the driver to scan for a suitable timer to use. Signed-off-by: Mark Salter <msalter@redhat.com> Signed-off-by: Aurelien Jacquiot <a-jacquiot@ti.com> Acked-by: Arnd Bergmann <arnd@arndb.de>
2011-10-04 16:12:20 +00:00
External Memory Interface
-------------------------
The emifa node describes a simple external bus controller found on some C6X
SoCs. This interface provides external busses with a number of chip selects.
Required properties:
- compatible: must be "ti,c64x+emifa", "simple-bus"
- reg: register area base and size
- #address-cells: must be 2 (chip-select + offset)
- #size-cells: must be 1
- ranges: mapping from EMIFA space to parent space
Optional properties:
- ti,dscr-dev-enable: Device ID if EMIF is enabled/disabled from DSCR
- ti,emifa-burst-priority:
Number of memory transfers after which the EMIF will elevate the priority
of the oldest command in the command FIFO. Setting this field to 255
disables this feature, thereby allowing old commands to stay in the FIFO
indefinitely.
- ti,emifa-ce-config:
Configuration values for each of the supported chip selects.
Example:
emifa@70000000 {
compatible = "ti,c64x+emifa", "simple-bus";
#address-cells = <2>;
#size-cells = <1>;
reg = <0x70000000 0x100>;
ranges = <0x2 0x0 0xa0000000 0x00000008
0x3 0x0 0xb0000000 0x00400000
0x4 0x0 0xc0000000 0x10000000
0x5 0x0 0xD0000000 0x10000000>;
ti,dscr-dev-enable = <13>;
ti,emifa-burst-priority = <255>;
ti,emifa-ce-config = <0x00240120
0x00240120
0x00240122
0x00240122>;
flash@3,0 {
#address-cells = <1>;
#size-cells = <1>;
compatible = "cfi-flash";
reg = <0x3 0x0 0x400000>;
bank-width = <1>;
device-width = <1>;
partition@0 {
reg = <0x0 0x400000>;
label = "NOR";
};
};
};
This shows a flash chip attached to chip select 3.
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