Hi Wolfgang,
Now that we keep the old speed on aligned access, I'm ok with the change and only see one typo in the comment.
The MPC5200 has a nasty problem that will cause silent data corruption when performing unaligned 16 or 32 byte accesses when reading from the local bus - typically this affects reading from flash. The problem can be easily shown:
=> md fc0c0000 10 fc0c0000: 323e4337 01626f6f 74636d64 3d72756e 2>C7.bootcmd=run fc0c0010: 206e6574 5f6e6673 00626f6f 7464656c net_nfs.bootdel fc0c0020: 61793d35 00626175 64726174 653d3131 ay=5.baudrate=11 fc0c0030: 35323030 00707265 626f6f74 3d656368 5200.preboot=ech => md fc0c0001 10 fc0c0001: 65636801 00000074 0000003d 00000020 ech....t...=... fc0c0011: 0000005f 00000000 00000074 00000061 ..._.......t...a fc0c0021: 00000000 00000064 00000065 00000035 .......d...e...5 fc0c0031: 00000000 00000062 0000003d 0000006f .......b...=...o => md.w fc0c0001 10 fc0c0001: 0000 3701 0000 6f74 0000 643d 0000 6e20 ..7...ot..d=..n fc0c0011: 0000 745f 0000 7300 0000 6f74 0000 6c61 ..t_..s...ot..la
This commit implements a workaround at least for the most blatant problem: using memcpy() from NOR flash. We rename the assembler routine into __memcpy() and provide a wrapper, which will use a byte-wise copy loop for unaligned source or target addresses when reading from NOR flash, and branch to the optimized __memcpy() in all other cases, thus minimizing the performance impact.
Tested on lite5200b and TQM5200S.
Signed-off-by: Wolfgang Denk wd@denx.de Cc: Detlev Zundel dzu@denx.de
Acked-by: Detlev Zundel dzu@denx.de
[...]
diff --git a/arch/powerpc/cpu/mpc5xxx/memcpy_mpc5200.c b/arch/powerpc/cpu/mpc5xxx/memcpy_mpc5200.c new file mode 100644 index 0000000..0950354 --- /dev/null +++ b/arch/powerpc/cpu/mpc5xxx/memcpy_mpc5200.c @@ -0,0 +1,71 @@ +/*
- (C) Copyright 2010
- Wolfgang Denk, DENX Software Engineering, wd@denx.de.
- See file CREDITS for list of people who contributed to this
- project.
- This program is free software; you can redistribute it and/or
- modify it under the terms of the GNU General Public License as
- published by the Free Software Foundation; either version 2 of
- the License, or (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place, Suite 330, Boston,
- MA 02111-1307 USA
- */
+/*
- This is a workaround for issues on the MPC5200, where unaligned
- 32-bit-accesses to the local bus will deliver corrupted data. This
- happens for example when trying to use memcpy() from an odd NOR
- flash address; the behaviour can be also seen when using "md" on an
- odd NOR flash address (but there it is not a bug in U-Boot, which
- only shows the behaviour of this processor).
- For memcpy(), we test if either the source or the target address
- are not 32 bit aligned, and - if so - if the source address is in
- NOR flash: in this case we perform a byte-wise (slow) then; for
^ +- copy
- aligned operations of non-flash areas we use the optimized (fast)
- real __memcpy(). This way we minimize the performance impact of
- this workaround.
- */
[...]
Cheers Detlev