Re: [PATCH] pata_it8213: MWDMA0 is unsupported

Sergei Shtylyov
2009-11-26T18:46:07Z

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@gmail.com>
>>>>>>>> ---
>>>>>>>> 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