Re: Opterons and setting the pci bus master bit

linux-os (Dick Johnson)
2005-09-30T17:32:57Z

On Fri, 30 Sep 2005, Mark Hounschell wrote:

> Problem, I have a number of dual processor Opterons that do not work
> with pci expansion chassis'. The reason that they do not work is because
> none of the cards discovered in the chassis get the pci bus master bit
> set in their command register. If I manually set this bit in our cards
> everything is fine. When we connect the same chassis to an Intel P4 box
> everything is fine. It looks like it is the kernel that sets this bit
> because we have never set it in any of our drivers, yet on the intel
> boxes it gets set. Why would this bit not be set when the chassis is
> connected to an Opteron. We are running 32-bit mode BTW. I am using a
> 2.6.11.9 kernel. Is this a motherboard problem or could this be a kernel
> problem?
>
> Thanks
> Mark

The PCI Busmaster bit should (read must) be set by the driver to enble
bus-mastering after the dma mask is set.

Commands are (in order):

pci_set_dma_mask(dev, 0xffffffffULL); // 32 bit DMA only
pci_set_drvdata(dev, NULL); // Harmless if unused
pci_set_power_state(dev, 0); // Turn it ON
pci_set_master(dev); // Make bus-master
pci_set_mwi(dev); // Check return, different code
pci_write_config_dword(dev, PCI_COMMAND, PCI_CONFIG_YOU_DEFINE);

Typical bus-master PCI_CONFIG_YOU_DEFINE is:
(PCI_COMMAND_MEMORY|PCI_COMMAND_MASTER|PCI_COMMAND_SERR)

Cheers,
Dick Johnson
Penguin : Linux version 2.6.13 on an i686 machine (5589.55 BogoMips).
Warning : 98.36% of all statistics are fiction.

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