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- =====================================
- Passing boot parameters to the kernel
- =====================================
- Boot parameters are represented as a TLV list in the memory. Please see
- arch/xtensa/include/asm/bootparam.h for definition of the bp_tag structure and
- tag value constants. First entry in the list must have type BP_TAG_FIRST, last
- entry must have type BP_TAG_LAST. The address of the first list entry is
- passed to the kernel in the register a2. The address type depends on MMU type:
- - For configurations without MMU, with region protection or with MPU the
- address must be the physical address.
- - For configurations with region translarion MMU or with MMUv3 and CONFIG_MMU=n
- the address must be a valid address in the current mapping. The kernel will
- not change the mapping on its own.
- - For configurations with MMUv2 the address must be a virtual address in the
- default virtual mapping (0xd0000000..0xffffffff).
- - For configurations with MMUv3 and CONFIG_MMU=y the address may be either a
- virtual or physical address. In either case it must be within the default
- virtual mapping. It is considered physical if it is within the range of
- physical addresses covered by the default KSEG mapping (XCHAL_KSEG_PADDR..
- XCHAL_KSEG_PADDR + XCHAL_KSEG_SIZE), otherwise it is considered virtual.
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