diff options
Diffstat (limited to 'Documentation/xtensa/booting.txt')
| -rw-r--r-- | Documentation/xtensa/booting.txt | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/xtensa/booting.txt b/Documentation/xtensa/booting.txt new file mode 100644 index 000000000000..402b33a2619f --- /dev/null +++ b/Documentation/xtensa/booting.txt @@ -0,0 +1,19 @@ +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. |