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).
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