[coreboot] Only UDMA/33 PATA on m57sli, UDMA/66 with factory BIOS

Harald Gutmann harald.gutmann at gmx.net
Tue Jul 7 21:32:59 CEST 2009

On Tuesday 07 July 2009 19:30:03 Peter Stuge wrote:
> Harald Gutmann wrote:
> > >     * hda: UDMA/33 compared to UDMA/66 with prop. BIOS
> >
> > My suggestion would be to open up a new ML-thread according to this
> > problem.
> Good idea.
> > It should be "easy" to fix, and I think that it has nothing to do
> > with the DMA modes itself, but with the "88pin-wire-cable-bit"
> Yep.
How does the bios check if an 80wire cable is used or not?
That means, on which event/basis/.../.../ we need to set those "magic bits"?

> > (but I don't know if it's for real a bit which needs to be set).
> Usually there is.
> > I also tried to investigate that problem, but ran out of time the
> > evening I started. (check kernel ide-drivers amd7xxx.c (or similar)
> > to find out what's going on there).
> I hope the bit we want isn't hidden in a chipset doc which we can't
> find. :\

According to some kernel sources and the differences in the pci-registers 
between proprietary bios and coreboot there are two values which are needed:


But, for PCI_VENDOR_ID_NVIDIA an offset of 0x10 has to be added, which means:

PCI registers on coreboot address 0x52 (from the IDE device) has value FF 
while proprietary has value 99. This is the so called "CABLE_BIT".

And as the second stuff needed, the AMD_UDMA_TIMING registers is as follows:
The kernel reads the whole address range from 0x60-0x92 and does some magic 
stuff to verify if everything is correct.

On the proprietary bios we have in this range in the pci-registers:
60: 00 00 c5 c7 00 00 00 00 00 00 00 00 00 00 00 00
On coreboot we have:
60: 00 00 c0 c0 00 00 00 00 00 00 00 00 00 00 00 00

Thats what to do, but when? - Maybe tomorrow.

> //Peter
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