htpt366 PCI latency value is really high

From: Mike Mattie
Date: Thu Apr 26 2007 - 09:50:26 EST


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Hello,

while hunting down some latency problems I found something quite odd.
The latency reported by lspci -v for the HTP203N card is enormous.

00:09.0 RAID bus controller: Triones Technologies, Inc. HPT302/302N
(rev 02) Subsystem: Triones Technologies, Inc. Unknown device 0001
Flags: bus master, 66MHz, medium devsel, latency 120, IRQ 17
I/O ports at ec00 [size=3D8]
I/O ports at e800 [size=3D4]
I/O ports at e400 [size=3D8]
I/O ports at e000 [size=3D4]
I/O ports at dc00 [size=3D256]
Expansion ROM at dffe0000 [disabled by cmd] [size=3D128K]
Capabilities: [60] Power Management version 2


I am assuming that the "latency" field here is the PCI latency timer
which means this card is a bus hog.=20

=46rom some reading on this issue linux methodically sets a sane value for=20
all the PCI cards it sets up, which looks normal on the rest of the system,=
=20
which is set to the value: 32

setting the value 32 with:

setpci -v -s "00:09.0" latency_timer=3D32

00:09.0 RAID bus controller: Triones Technologies, Inc. HPT302/302N (rev 02)
Subsystem: Triones Technologies, Inc. Unknown device 0001
Flags: bus master, 66MHz, medium devsel, latency 48, IRQ 17
I/O ports at ec00 [size=3D8]
I/O ports at e800 [size=3D4]
I/O ports at e400 [size=3D8]
I/O ports at e000 [size=3D4]
I/O ports at dc00 [size=3D256]
Expansion ROM at dffe0000 [disabled by cmd] [size=3D128K]
Capabilities: [60] Power Management version 2

Results in 48, which is not what I asked, but hopefully this is
linux doing the right thing.

I know this chipset is pretty brain-damaged, but is this
high latency value a work-around for broken hardware, or
just a oversight ?

Cheers,
Mike Mattie - codermattie@xxxxxxxxx

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