[linux-dvb] Re: Removing PCI-latency settings from CVS

[Oliver Endriss <o.endriss@gmx.de>]

On Friday 01 August 2003 12:12, Dr. Werner Fink wrote:
> On Fri, Aug 01, 2003 at 09:26:45AM +0200, Oliver Endriss wrote:
> > Thinking about it I also came to the conclusion that it is a bad
> > idea to nail the latency setting to 64. Either it should be done by
> > calculating the latency *correctly* or it should be left to BIOS,
> > kernel, setpci etc. I'll disable this code in DVB CVS.
> > (There are rumours that it was added by aliens who have technology
> > to fly from Venus to Mars ;-)
>
> Wouldn't it be better to do the calculating instead of breaking other
> systems which do it better _with_ a latency of 64?

Sure, if someone really *knows* how to do that correctly. ;-)
(I don't know enough about the PCI bus specs.)

I considered the following:
- DVB kernel does not set this value.
- If required you can simply put setpci into your local boot script.
- Many bioses allow to specify the default latency value.
  (64 seems to be a common default value.)
- The value 64 produces artefacts on some systems.
- A built-in value makes it harder to use setpci to specify the correct
  value. You have to call setpci each time after the driver has been 
  loaded.
- I'm not sure whether the DVB driver ist the correct place to do it.

Anyway, if you prefer I could make it a module parameter.
(default is 0 --> no change, otherwise set the specified value).

Any opinions?

Oliver


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