From: Jeff Garzik <jgarzik@pobox.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [rfc/patch] libata -- port configurable delays
Date: Fri, 13 May 2005 19:21:43 -0400 [thread overview]
Message-ID: <42853687.1050402@pobox.com> (raw)
In-Reply-To: <1116019231.26693.499.camel@localhost.localdomain>
Alan Cox wrote:
> On Gwe, 2005-05-13 at 19:58, Benjamin LaHaise wrote:
>
>>is available at http://www.kvack.org/~bcrl/simple-aio-min_nr.c).
>>Before this patch __delay() is the number one entry in oprofile
>>results for this workload. Does this look like a reasonable approach
>>for chipsets that aren't completely braindead? Cheers,
>
>
> If your chipset implements the 400nS lockout in hardware it certainly
> seems to make sense. Nice to know someone has put it in hardware
No, it's just mostly irrelevant under SATA.
Under SATA you are -not- talking to a device when you touch
Status/AltStatus, you are talking to the host controller. Specifically,
you're talking to a controller buffer that stores a copy of the ATA
shadow registers.
The ATA registers are transmitted to the device in a single packet,
called a FIS, when the Command or Device Control register is written.
When the device updates its status, or completes a command, it sends a
FIS from device to controller, instructing the controller to update its
cached copy of the Status register.
You're bitbanging a buffer, in SATA.
Jeff
next prev parent reply other threads:[~2005-05-13 23:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-13 18:58 [rfc/patch] libata -- port configurable delays Benjamin LaHaise
2005-05-13 19:13 ` Jeff Garzik
2005-05-13 20:03 ` Benjamin LaHaise
2005-05-13 21:52 ` Alan Cox
2005-05-13 23:07 ` Jeff Garzik
2005-05-14 1:51 ` Mark Lord
2005-05-13 19:17 ` Jeff Garzik
2005-05-13 21:20 ` Alan Cox
2005-05-13 23:21 ` Jeff Garzik [this message]
2005-05-14 21:11 ` Alan Cox
2005-05-14 21:47 ` Jeff Garzik
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