From: Sergei Shtylyov <sshtylyov@mvista.com>
To: Pallav Bose <pallavbose@gmail.com>
Cc: linux-ide@vger.kernel.org
Subject: Re: Disabling Command Completion Coalescing (CCC) in SATA AHCI
Date: Fri, 20 May 2011 14:49:27 +0400 [thread overview]
Message-ID: <4DD64737.10706@ru.mvista.com> (raw)
In-Reply-To: <BANLkTinPkdTkOQHNnPHwtXq2SMCo-uAALA@mail.gmail.com>
Hello.
On 20-05-2011 0:32, Pallav Bose wrote:
> I'm working on 2.6.35.9 version of the Linux kernel and am trying to
> disable Command Completion Coalescing. I have Native Command Queuing
> enabled by activating the RAID mode through the BIOS.
> I was looking at the Serial ATA AHCI 1.3 Specification and found on
> page 115 that -
> The CCC feature is only in use when CCC_CTL.EN is set to ‘1’. If
> CCC_CTL.EN is set to ‘0’, no CCC interrupts shall be generated.
> Next, I had a look at the relevant code (namely, the files concerning
> AHCI) for this version of the kernel but wasn't able to make any
> progress. I found the following enum constant - HOST_CAP_CCC = (1<<
> 7) - in drivers/ata/ahci.h, but I'm not sure how this should be
> modified to disable command coalescing. I did set HOST_CAP_CCC to 0
> but through some experiments that I conducted, I found that responses
> were being batched.
This constant is only used to report the controller capability, I see no
other code depending on it, hence there doesn't seem to be any CCC support...
[...]
> The mass storage controller in the system is: Promise Technology, Inc.
> PDC20268 (Ultra100 TX2) (rev 02),
I don't understand. This controller is not AHCI, and not even SATA one.
> and the HDD being used is: WD Caviar Black (Model number - WD1001FALS).
WBR, Sergei
prev parent reply other threads:[~2011-05-20 10:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-19 20:32 Disabling Command Completion Coalescing (CCC) in SATA AHCI Pallav Bose
2011-05-20 2:14 ` Robert Hancock
2011-05-23 14:36 ` Pallav Bose
2011-05-23 20:27 ` Robert Hancock
2011-05-24 5:16 ` Pallav Bose
2011-06-01 18:25 ` Pallav Bose
2011-05-20 10:49 ` Sergei Shtylyov [this message]
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