booting.rst (1314B)
1===================================== 2Passing boot parameters to the kernel 3===================================== 4 5Boot parameters are represented as a TLV list in the memory. Please see 6arch/xtensa/include/asm/bootparam.h for definition of the bp_tag structure and 7tag value constants. First entry in the list must have type BP_TAG_FIRST, last 8entry must have type BP_TAG_LAST. The address of the first list entry is 9passed to the kernel in the register a2. The address type depends on MMU type: 10 11- For configurations without MMU, with region protection or with MPU the 12 address must be the physical address. 13- For configurations with region translarion MMU or with MMUv3 and CONFIG_MMU=n 14 the address must be a valid address in the current mapping. The kernel will 15 not change the mapping on its own. 16- For configurations with MMUv2 the address must be a virtual address in the 17 default virtual mapping (0xd0000000..0xffffffff). 18- For configurations with MMUv3 and CONFIG_MMU=y the address may be either a 19 virtual or physical address. In either case it must be within the default 20 virtual mapping. It is considered physical if it is within the range of 21 physical addresses covered by the default KSEG mapping (XCHAL_KSEG_PADDR.. 22 XCHAL_KSEG_PADDR + XCHAL_KSEG_SIZE), otherwise it is considered virtual.