busmaster/latency for video

[Michel Lanners]

On   7 Oct, this message from Geert Uytterhoeven echoed through cyberspace:
> On Thu, 7 Oct 1999, Michel Lanners wrote:
>> On   6 Oct, this message from Ryan Nielsen echoed through cyberspace:
>> > PCI_COMMAND_MASTER is not enabled and latency = 0 for the ultimate rez video card, and pci_write_config_*
>> > do not change them. latency = 32 and mastering is enabled for all the other cards in the machine,
>> > 
>> > should they be enabled ?
>> 
>> That probably means the card doesn't support them.
>> 
>> Normal graphic cards have no need for mastership. Only those with video
>> inputs need it, in order to transfer video data into the framebuffer
>> without CPU help.
> 
> Many recent graphics chips to support bus mastering, especially the AGP ones.

Ah, but in that case Apple's OF should enable bus mastering. If I read
well between the lines of Apple's docs, OF should set a few default
parameters on all PCI devices, among which bus mastering. I'm not sure
about latency, though...

Michel

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