Re: serverworks CSB5 IDE: DMA disabled on secondary channel

From: Robert Hancock
Date: Thu Jul 17 2008 - 21:09:23 EST

Frantisek Hanzlik wrote:
Server with Intel SHG2 board, servervorks CSB5 rev. 93: After
upgrade from kernel 2.6.22 (IDE serverworks driver) to 2.6.25
(Fedora 9: libata+pata_serverworks driver), SW RAID1 performance
is very bad. Problem is probably with secondary IDE channel,
which has disabled DMA:

# hdparm -Tt /dev/sda
Timing cached reads: 828 MB in 2.00 seconds = 414.26 MB/sec
Timing buffered disk reads: 210 MB in 3.01 seconds = 69.83 MB/sec

# hdparm -Tt /dev/sdb
Timing cached reads: 408 MB in 2.00 seconds = 203.72 MB/sec
Timing buffered disk reads: 6 MB in 3.05 seconds = 1.96 MB/sec

dmesg output:
libata version 3.00 loaded.
PCI: Setting latency timer of device 0000:00:0f.1 to 64
scsi0 : pata_serverworks
scsi1 : pata_serverworks
ata1: PATA max UDMA/100 cmd 0x1f0 ctl 0x3f6 bmdma 0x2440 irq 14
ata2: PATA max UDMA/100 cmd 0x170 ctl 0x376 bmdma 0x2448 irq 15
ata1.00: ATA-7: ST3400620A, 3.AAE, max UDMA/100
ata1.00: 781422768 sectors, multi 16: LBA48
ata1.01: ATAPI: TOSHIBA DVD-ROM SD-M1612, 1004, max UDMA/33
ata1.00: configured for UDMA/100
ata1.01: configured for UDMA/33
ata2.00: ATA-7: ST3400620A, 3.AAE, max UDMA/100
ata2.00: 781422768 sectors, multi 16: LBA48
ata2.01: ATAPI: CD-W540E, 1.0D, max UDMA/33
ata2.00: simplex DMA is claimed by other device, disabling DMA
ata2.01: simplex DMA is claimed by other device, disabling DMA
ata2.00: configured for PIO4
ata2.01: configured for PIO4

# lsmod|grep ata
pata_serverworks 10496 8
pata_acpi 8320 0
libata 127328 2 pata_serverworks,pata_acpi
scsi_mod 120948 4 sg,sr_mod,libata,sd_mod

It's some sort of pata_serverworks bug, or is needed any special
setup for this driver to work?
What is "simplex DMA" term?

It means this controller can only do DMA on the primary or secondary channel, not both at the same time. It looks like libata currently deals with this by disabling DMA on the secondary channel. Not sure how the old IDE stuff handled it?

ServerWorks IDE always seemed to pretty much suck, I always got the impression that they stuck it on there as an afterthought just to operate a CD drive enough to install the OS..
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