Re: parallel port *slow* (and plip probs.)

On Fri, Jul 16, 2004 at 11:59:39AM +0100, Andrew Gordon wrote:
> On Fri, 16 Jul 2004, Palle Girgensohn wrote:
> >
> > --On torsdag, juli 15, 2004 20.33.28 -0400 Allan Fields <bsd_at_afields.ca>
> > wrote:
> >
> > > On Thu, Jul 15, 2004 at 11:36:30PM +0100, Antony T Curtis wrote:
> > >> On Thu, 2004-07-15 at 22:07, Palle Girgensohn wrote:
> > >> > Only, the flags don't work, nothing seems to happen?
> > >
> > > Did you set to ECP mode in your BIOS?
> >
> > ECP+EPP
> 
> Should be fine
> 
> However, the key thing in that line is the "drq 3" - ECP mode will not
> work without a drq setting (and IIRC you just get left in SPP mode without
> any diagnostics).  The hints listed above don't appear to include one.
> 
> > > I've had ECP working in 5.1 & 5.2 using device.hints as I've been
> > > misusing a machine as PLIP router to provide old laptop w/ network
> > > since PCMCIA interface isn't working w/ installed kernel.
> 
> I'm fairly sure this is irrelevant, since PLIP just does bit-bashing in
> the port registers that control the pins directly and doesn't use any of
> the parallel port modes.
>
> So, your port probably isn't really working in ECP mode but you don't care
> for that application.

Yup, you're right, and performance isn't any better either way.
At the time I enabled it, I thought it would help, but doesn't.

plip really eats up the resources (explained in code or man page
why.)  So while useful for short term use absent any other setup,
it bogs a machine down significantly -- with interrupt activity and
sets splhigh()

> [Disclaimer: I've not really used parallel ports since 4.x, but I don't
> think anything of significance has changed.   Certainly 'ECP must use
> ISA DMA' is a fundamental feature of the hardware].

Yes: EPP requires IRQ, while ECP requires both DMA and an IRQ.  So unless
it uses DMA 3 setting implicitly, I'd follow the logic.

- Allan