2019-04-18 17:34:34 +00:00
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=====================================
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Passing boot parameters to the kernel
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=====================================
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2018-11-15 01:48:07 +00:00
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Boot parameters are represented as a TLV list in the memory. Please see
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arch/xtensa/include/asm/bootparam.h for definition of the bp_tag structure and
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tag value constants. First entry in the list must have type BP_TAG_FIRST, last
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entry must have type BP_TAG_LAST. The address of the first list entry is
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passed to the kernel in the register a2. The address type depends on MMU type:
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2019-04-18 17:34:34 +00:00
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2018-11-15 01:48:07 +00:00
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- For configurations without MMU, with region protection or with MPU the
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address must be the physical address.
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- For configurations with region translarion MMU or with MMUv3 and CONFIG_MMU=n
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the address must be a valid address in the current mapping. The kernel will
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not change the mapping on its own.
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- For configurations with MMUv2 the address must be a virtual address in the
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default virtual mapping (0xd0000000..0xffffffff).
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- For configurations with MMUv3 and CONFIG_MMU=y the address may be either a
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virtual or physical address. In either case it must be within the default
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virtual mapping. It is considered physical if it is within the range of
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physical addresses covered by the default KSEG mapping (XCHAL_KSEG_PADDR..
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XCHAL_KSEG_PADDR + XCHAL_KSEG_SIZE), otherwise it is considered virtual.
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