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

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Message-ID: <4B0EC52B.2070805@ru.mvista.com>
Date:	Thu, 26 Nov 2009 21:12:59 +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

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@...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?

>>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.

> --
> Bartlomiej Zolnierkiewicz

MBR, Sergei
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