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author | Max Filippov <jcmvbkbc@gmail.com> | 2018-11-15 04:48:07 +0300 |
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committer | Max Filippov <jcmvbkbc@gmail.com> | 2019-02-04 05:06:19 +0300 |
commit | 05bdebd546db924f9bcb4c524c436a016b0c8fca (patch) | |
tree | 07137e96d783776a74a229fba43ac41274a7e29b /Documentation/xtensa/booting.txt | |
parent | 8834f5600cf3c8db365e18a3d5cac2c2780c81e5 (diff) | |
download | linux-05bdebd546db924f9bcb4c524c436a016b0c8fca.tar.xz |
xtensa: document boot parameter passing
Add booting.txt to Documentation/xtensa with description of boot
parameters representation and passing to the kernel.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
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. |