MACE DMA problem on Powermac 7300

Risto Suominen risto.suominen at
Tue Dec 8 03:22:23 EST 2009

Hi, Ben,

2009/12/7, Benjamin Herrenschmidt <benh at>:
> Cache coherency bugs in the chipset or HW bugs in DBDMA, we've been
> seeing those on/off on those old apple chipsets...
> Try forcing a 32 bytes alignment ?
You're thinking of placing the DMA descriptors on different cache lines?

That's excactly what I did with de2104x. But it was easier, I think.
The chip handled its own DMA, and by writing a skip value to a
register... I don't know this GC DMA controller well enough and
haven't found the documentation either...

But I tried the de21041 board with unmodified driver on this 7300, and
it works. The problem was on a 5500.


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