was recently handed a MIPS-based dev board (can't name the vendor,
NDA) that *typically* runs in LE mode but, because of a proprietary
binary that must be run on the board and was compiled as BE, has to be
run in BE mode.
the vendor supplied a yoctoproject layer that seems to work fine
but, in changing the DEFAULTTUNE to big-endian, the following patch
had to be applied to the 3.14 kernel tree to the file
arch/mips/include/asm/io.h in order to get output from the console
port as the system was booting:
326c326,333
< *__mem = __val; \
---
> { \
> if (sizeof(type) == sizeof(u32)) \
> { \
> *__mem = __cpu_to_le32(__val); \
> } \
> else \
> *__mem = __val; \
> } \
356a364
> { \
357a366,368
> if (sizeof(type) == sizeof(u32)) \
> __val = __cpu_to_le32(__val); \
> } \
without that patch, the initial conclusion was that the board was
just hanging at boot, but i was told, no, it was booting, there was
just no output at the console port. applied the patch and, voila.
can someone explain *precisely* what the above is doing? i am by no
means a MIPS expert, but clearly the above is doing some sort of
explicit BE/LE conversion. can anyone supply more detail? thanks.
rday
--
========================================================================
Robert P. J. Day Ottawa, Ontario, CANADA
http://crashcourse.ca
Twitter: http://twitter.com/rpjday
LinkedIn: http://ca.linkedin.com/in/rpjday
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