|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.