Re: [PATCH] pata_it8213: MWDMA0 is unsupported

Bartlomiej Zolnierkiewicz
2009-11-26T18:28:04Z

On Thursday 26 November 2009 07:12:59 pm Sergei Shtylyov wrote:
> Bartlomiej Zolnierkiewicz 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

> >>All data sheets including original Intel ones are a complete crap when it
> >>comes to explicitly documenting this behavior.
>
> > OTOH all drivers set TIMEx for MWDMA0 currently.. ?
>
> ... which would give a grossly overclocked timing.

Except ata_piix which blacklists MWDMA0 for _all_ PATA controllers.. :)

I'm leaving my patches as they were for now, unless somebody wants to
untangle this mess this is a safest and quickest way forward..

--
Bartlomiej Zolnierkiewicz