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- * OpenPIC and its interrupt numbers on Freescale's e500/e600 cores
- The OpenPIC specification does not specify which interrupt source has to
- become which interrupt number. This is up to the software implementation
- of the interrupt controller. The only requirement is that every
- interrupt source has to have an unique interrupt number / vector number.
- To accomplish this the current implementation assigns the number zero to
- the first source, the number one to the second source and so on until
- all interrupt sources have their unique number.
- Usually the assigned vector number equals the interrupt number mentioned
- in the documentation for a given core / CPU. This is however not true
- for the e500 cores (MPC85XX CPUs) where the documentation distinguishes
- between internal and external interrupt sources and starts counting at
- zero for both of them.
- So what to write for external interrupt source X or internal interrupt
- source Y into the device tree? Here is an example:
- The memory map for the interrupt controller in the MPC8544[0] shows,
- that the first interrupt source starts at 0x5_0000 (PIC Register Address
- Map-Interrupt Source Configuration Registers). This source becomes the
- number zero therefore:
- External interrupt 0 = interrupt number 0
- External interrupt 1 = interrupt number 1
- External interrupt 2 = interrupt number 2
- ...
- Every interrupt number allocates 0x20 bytes register space. So to get
- its number it is sufficient to shift the lower 16bits to right by five.
- So for the external interrupt 10 we have:
- 0x0140 >> 5 = 10
- After the external sources, the internal sources follow. The in core I2C
- controller on the MPC8544 for instance has the internal source number
- 27. Oo obtain its interrupt number we take the lower 16bits of its memory
- address (0x5_0560) and shift it right:
- 0x0560 >> 5 = 43
- Therefore the I2C device node for the MPC8544 CPU has to have the
- interrupt number 43 specified in the device tree.
- [0] MPC8544E PowerQUICCTM III, Integrated Host Processor Family Reference Manual
- MPC8544ERM Rev. 1 10/2007
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