Re: [PATCH] pata_it8213: MWDMA0 is unsupported

[Sergei Shtylyov]

Hello, I wrote:

> > > > > > > > MWDMA0 timings cannot be met with the PIIX based controller
> > > > > > > > programming interface.

> > > > > > > > This change should be safe as this is how we have been doing
> > > > > > > > things in IDE it8213 host driver for years.

> > > > > > > > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>
> > > > > > > > ---
> > > > > > > > Verified with the documentation (similar case as with pata_efar).

> > > > > > > Uhhh, no...

> > > > > > > Too many damn drivers.

> > > > > > > Too much damn duplication.

> > > > > > > Too much damn subtle differences here and there.

> > > > > > > The hardware is probably fine for MWMDA0 when it comes to 
> > > > > > > pata_{efar,it8213},
> > > > > > > it just not documented properly in the data sheet.

> > > > > >   How so with pata_efar? The active/recovery bitfields are still 
> > > > > > 2-bit wide, no?

> > > > > Yes but when TIMEx bit is disabled we are using XFER_PIO_SLOW timings.

> > >    600 ns cycle vs spec'ed 480 ns? Is it really worth it?

> > 960 ns actually

>    That table you're looking at (probably in the SLC90E66 datasheet?) 
> must be screwed up. 960 ns is used for command cycles, according to 
> Intel's docs, data cycles run at 600 ns...

   Well, after doublke checking 82371AB datasheet has 660 ns, and ICH PRM 
has 900 ns. Not sure where I got what I've cited now, perhaps in some older 
version of PRM... what a mess indeed. :-/

MBR, Sergei
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