linux-kernel - Re: [PATCH] pata_it8213: MWDMA0 is unsupported

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Message-ID: <4B0ECD27.7050302@ru.mvista.com>
Date:	Thu, 26 Nov 2009 21:47:03 +0300
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pata_it8213: MWDMA0 is unsupported

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@...il.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
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