Problems with NCQ

[DavideCavestro]

I am not able to use my new hard disk NCQ capabilities.

I know the SATA controller supports it and even the hard disk.
My configuration is:
- an Asus A8V-MX motherboard, equipped with a VT8251 South Bridge
- a 150 GB Velociraptor hard disk (WDC WD1500HLFS-01G6U0)

But I continue to get this message in dmesg:

ata1.00: 293046768 sectors, multi 16: LBA48 NCQ (depth 0/32)

which means I have NCQ disabled (see libATA FAQ)

I have tried on vanilla kernels 2.6.29, 2.6.28.7 and 2.6.27 but without success.

I will attach the output of some commands.
Can someone give me some hints?

Thank you

[blinky]

googled for "VT8251 ncq linux"

VT8251 Linux Support - tkArena Forums

[DavideCavestro]

All I can understand is that NCQ is disabled on sata_via driver (see Serial ATA (SATA) Linux hardware/driver status report), but I am using the ahci driver.

Somene knows is NCQ is disabled even on ahci driver for VT8251?

In other words I would like to know if there is a driver that supports NCQ for VT8251 (see Sata Drive Mode Option Help - LinuxQuestions.org)

Another detail: I'm booting the kernel with "pci=nomsi" parameter, to prevent another problem (something similar to https://bugs.launchpad.net/ubuntu/+s...ux/+bug/206026)

[HROAdmin26]

You may want to follow up on this bug report and find out the current status. As noted, when this e-mail was posted (Jan 2007), even the VIA SATA driver for Windows had NCQ disabled.

Google "ncq ahci vt8251" => First Link

> Of course, I'm now curious as to why NCQ is disabled on VIA AHCI controllers.
> Is there a known hardware bug I should be wary of, or is it just a case of
> being cautious due to the other issues with the VT8251 (in which case I'll
> try enabling it and reporting back)?

Yeap, there is a known NCQ problem with vt8251. Can't find the original
bug report now tho.

commit 71f0737b2889b86f774a94afaf1342c2c0d61cb5
tree e983d3f4c3fccad0679aa8ae18a0c3ce91bfafe7
parent 8fa29b23d9e0ef976dc578aab98297d4f24f70da
author Tejun Heo <[EMAIL PROTECTED]> 1150899168 +0900
committer Jeff Garzik <[EMAIL PROTECTED]> 1151032959 -0400

[PATCH] ahci: disable NCQ support on vt8251

vt8251 chokes on NCQ commands. Two different disks from different
vendors are showing the same symptom and it seems that the windows
driver from via doesn't support NCQ either. Disable NCQ support on
this controller for the time being.

[DavideCavestro]

Bad news
since I was only able to find generic bugs (Bug 7372 &ndash; Unusable system (ie slow) when copying large files.) not strictly related with my issue, I started searching on kernel sources.

On linux-2.6.29/drivers/ata/ahci.c I found this code snippet

/* board_ahci_vt8251 */
{
AHCI_HFLAGS (AHCI_HFLAG_NO_NCQ | AHCI_HFLAG_NO_PMP),
.flags = AHCI_FLAG_COMMON,
.pio_mask = 0x1f, /* pio0-4 */
.udma_mask = ATA_UDMA6,
.port_ops = &ahci_vt8251_ops,
},

so I think the flag AHCI_HFLAG_NO_NCQ means NCQ is actually disabled even on AHCI driver.

[DavideCavestro]

Here you are the thread I opened to ask for support at VIA's

Someone can use NCQ with VT8251? - tkArena Forums