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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
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Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+=====================================
+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.