diff options
Diffstat (limited to 'cpu/mpc824x/cpu_init.c')
| -rw-r--r-- | cpu/mpc824x/cpu_init.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/cpu/mpc824x/cpu_init.c b/cpu/mpc824x/cpu_init.c index 965f4fd5ed..7871031b97 100644 --- a/cpu/mpc824x/cpu_init.c +++ b/cpu/mpc824x/cpu_init.c @@ -106,6 +106,21 @@ cpu_init_f (void) CONFIG_READ_BYTE(AMBOR,val); CONFIG_WRITE_BYTE(AMBOR,val|0x1); +#if 0 + /* + * The following bug only affects older (XPC8245) processors. + * DMA transfers initiated by external devices get corrupted due + * to a hardware scheduling problem. + * + * The effect is: + * when transferring X words, the first 32 words are transferred + * OK, the next 3 x 32 words are 'old' data (from previous DMA) + * while the rest of the X words is xferred fine. + * + * Disabling 3 of the 4 32 word hardware buffers solves the problem + * with no significant performance loss. + */ + CONFIG_READ_BYTE(PCMBCR,val); /* in order not to corrupt data which is being read over the PCI bus * with the PPC as slave, we need to reduce the number of PCMRBs to 1, @@ -117,10 +132,8 @@ cpu_init_f (void) #else CONFIG_WRITE_BYTE(PCMBCR,(val|0x80)); /* 2 PCMRBs */ CONFIG_WRITE_BYTE(PCMBCR,(val|0x40)); /* 3 PCMRBs */ - /* default, 4 PCMRBs are used, so don't change the - * register is this is _really_ what you want: data - * corruption with no performance gain - */ + /* default, 4 PCMRBs are used */ +#endif #endif #endif |