From: Mark Lord <lkml@rtr.ca>
To: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Jeff Garzik <jeff@garzik.org>,
linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>
Subject: Re: What's in libata-dev.git
Date: Wed, 04 Oct 2006 14:48:24 -0400 [thread overview]
Message-ID: <452401F8.5000004@rtr.ca> (raw)
In-Reply-To: <4523F77B.1030908@ru.mvista.com>
Sergei Shtylyov wrote:
>..
>> I suspect Sergei simply had a bad controller card at the time.
>
> I can hardly imagine the reason why a PCI IDE controller (that was
> something like VT82C586 I think) would need to mess with the sector
> count reg. in PIO mode and return "command aborted" in the error reg...
> That was the exact sympthom IIRC.
Ahh.. well, if it just returned command aborted, then Jeff's original
change would present no real danger --> any occurances would be detected.
But to answer the imaginative question, the *reason* why a PCI (or VLB) IDE
controller would mess with the registers, is because the makers have this
nasty habit of wanting to do data prefetching (and posting) to speed up
transfers, particularly PIO transfers. And the only way they can do the
prefetching/posting "safely", is to snoop the taskfile registers and have
the contoller "know" their meanings.
This has lead to all kinds of lunacies, like the RZ1000, CMD640, and other
memorable disasters of mis-implementation.
Cheers!
next prev parent reply other threads:[~2006-10-04 18:48 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-11 13:22 What's in libata-dev.git Jeff Garzik
2006-09-11 13:35 ` Sergei Shtylyov
2006-09-11 13:37 ` Jeff Garzik
2006-09-11 13:47 ` Sergei Shtylyov
2006-09-11 13:49 ` Jeff Garzik
2006-09-11 14:53 ` Linus Torvalds
2006-09-11 15:24 ` Jeff Garzik
2006-09-12 8:42 ` Helge Hafting
2006-09-13 1:50 ` Tejun Heo
2006-09-11 15:02 ` Alan Cox
2006-09-11 14:44 ` Jeff Garzik
2006-09-11 15:05 ` Sergei Shtylyov
2006-09-11 15:28 ` Alan Cox
2006-09-11 15:21 ` Sergei Shtylyov
2006-09-11 15:37 ` Jens Axboe
2006-09-11 15:50 ` Jeff Garzik
2006-09-11 20:01 ` Jens Axboe
2006-09-11 20:14 ` Jeff Garzik
2006-09-11 20:23 ` Jens Axboe
2006-09-11 16:04 ` Linus Torvalds
2006-09-11 19:51 ` Jens Axboe
2006-09-11 23:00 ` Alan Cox
2006-09-11 22:53 ` Greg Freemyer
2006-09-12 5:22 ` Jens Axboe
2006-09-11 16:26 ` Alan Cox
2006-09-11 19:51 ` Jens Axboe
2006-09-11 15:06 ` Jens Axboe
2006-10-04 17:57 ` Mark Lord
2006-10-04 18:03 ` Sergei Shtylyov
2006-10-04 18:48 ` Mark Lord [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-01-24 7:26 Jeff Garzik
2007-01-24 17:26 ` Mark Lord
2007-01-24 19:19 ` Jeff Garzik
2006-05-24 7:08 Jeff Garzik
2006-04-18 9:54 Jeff Garzik
2006-04-18 15:07 ` Bastiaan Jacques
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