> -----Original Message----- > From: openocd-development-boun...@lists.berlios.de [mailto:openocd- > development-boun...@lists.berlios.de] On Behalf Of David Claffey > Sent: donderdag 11 juni 2009 23:18 > To: openocd-development > Subject: [Openocd-development] mips32 big endian fix > > A patch is needed for MIPS big endian (elf32-tradbigmips) targets. Perhaps > I'm the first to test trunk with a MIPS big endian target. > > If "-endian big" is not set in target create, the endianess defaults to > little. > mw and md commands will still work, but binary file loads will have the > incorrect word order loaded into memory. > > The EJTAG processor access data register (PrAcc) is little endian regardless > of the CPU endianness; it is always loaded LSB first. This is confirmed by > the fact that mips_ejtag_drscan_32() uses buf_set_u32() to load the scan > field; > buf_set_u32() is a little-endian formatter. For big endian targets, data > buffers have to be modified so the LSB of each u32 or u16 is at the lower > (first) memory location. > > The attached patch for src/target/mips_m4k.c fixes the problem. > > Included is a patch for src/target/mips_ejtag.c that fixes the case of a big > endian host. Again it is related to PrAcc. If the drscan out_value word > order is set using buf_set_u32() then it makes sense to also fixup the > in_value with buf_get_u32(); a symmetry argument. This has no affect on > little endian hosts. > David, I strongly doubt your patch is required. AFAIK OpenOCD already modifies the loaded data for correct endianess at a higher level. Secondly I think endianess conversions should not be done inside a target specific file. I'm using OpenOCD with a MIPS target (AU1100) as well which is also big endian. I've configured OpenOCD to use little endian mode and that seems to be the proper setting. A thing to look out for is that the MIPS EJTAG interface may do the endian conversion for you. Is the order of the special function registers correct when OpenOCD is in little endian mode? This the case with 'my' AU1100 target. You might want to check that first. If the special function registers read correctly in little endian mode then you'll need to modify the endianess of the binary file before loading it with OpenOCD. There are tools to do that. If I'm correct the bootloader Yamon comes with a tool called 'smunge' which can be used to modify the endianess of a file.
Nico Coesel _______________________________________________ Openocd-development mailing list Openocd-development@lists.berlios.de https://lists.berlios.de/mailman/listinfo/openocd-development
