Date: Sun, 30 Nov 2003 19:22:32 +0100
From: Jens Axboe <axboe@suse.de>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: Vojtech Pavlik <vojtech@suse.cz>,
       Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
       "Prakash K. Cheemplavam" <prakashkc@gmx.de>, marcush@onlinehome.de,
       linux-kernel@vger.kernel.org, eric_mudama@Maxtor.com
Subject: Re: Silicon Image 3112A SATA trouble
Message-ID: <20031130182232.GF6454@suse.de>
References: <3FC36057.40108@gmx.de> <3FCA1DD3.70004@pobox.com> <20031130165146.GY10679@suse.de> <200311301758.53885.bzolnier@elka.pw.edu.pl> <3FCA2380.1050902@pobox.com> <20031130171006.GA10679@suse.de> <20031130175649.GA18670@ucw.cz> <20031130181723.GD6454@suse.de> <3FCA34A6.3010600@pobox.com>
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Sender: linux-kernel-owner@vger.kernel.org

On Sun, Nov 30 2003, Jeff Garzik wrote:
> Jens Axboe wrote:
> >On Sun, Nov 30 2003, Vojtech Pavlik wrote:
> >
> >>On Sun, Nov 30, 2003 at 06:10:06PM +0100, Jens Axboe wrote:
> >>
> >>
> >>>On Sun, Nov 30 2003, Jeff Garzik wrote:
> >>>
> >>>>Bartlomiej Zolnierkiewicz wrote:
> >>>>
> >>>>>On Sunday 30 of November 2003 17:51, Jens Axboe wrote:
> >>>>>
> >>>>>>>Tangent:  My non-pessimistic fix will involve submitting a single 
> >>>>>>>sector
> >>>>>>>DMA r/w taskfile manually, then proceeding with the remaining 
> >>>>>>>sectors in
> >>>>>>>another r/w taskfile.  This doubles the interrupts on the affected
> >>>>>>>chipset/drive combos, but still allows large requests.  I'm not 
> >>>>>>>terribly
> >>>>>>
> >>>>>>Or split the request 50/50.
> >>>>>
> >>>>>
> >>>>>We can't - hardware will lock up.
> >>>>
> >>>>Well, the constraint we must satisfy is
> >>>>
> >>>>	sector_count % 15 != 1
> >>>
> >>>	(sector_count % 15 != 1) && (sector_count != 1)
> >>>
> >>>to be more precise :)
> >>
> >>I think you wanted to say:
> >>
> >>	(sector_count % 15 != 1) || (sector_count == 1)
> >
> >
> >Ehm no, I don't think so... To my knowledge, sector_count == 1 is ok. If
> >not, the hardware would be seriously screwed (ok it is already) beyond
> >software fixups.
> 
> 
> Now that you've kicked my brain into action, yes, sector_count==1 is ok. 
>  It's all about limiting the data FIS...  and with sector_count==1 
> there is no worry about the data FIS in this case.

Ah, my line wasn't completely clear (to say the least)... So to clear
all doubts:

	if ((sector_count % 15 == 1) && (sector_count != 1))
		errata path

Agree?

-- 
Jens Axboe

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