PIIX4, AC32500 a DMA

[Petr Soucek]

Zdravim,

mam motherboard GA-586T2 od Gigabyte a zarazi me, ze po nastartovani
Linuxu (RHL5.2 s jadrem 2.2.9ac1) se disabluje DMA u HD, ackoliv ho i
radic i harddisk podporuji:

PIIX4: IDE controller on PCI bus 00 dev 39
PIIX4: not 100% native mode: will probe irqs later
    ide0: BM-DMA at 0xf000-0xf007, BIOS settings: hda:pio, hdb:pio
    ide1: BM-DMA at 0xf008-0xf00f, BIOS settings: hdc:pio, hdd:pio
hda: WDC AC32500H, ATA DISK drive
hdb: HITACHI CDR-8130, ATAPI CDROM drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
hda: Disabling (U)DMA for WDC AC32500H
hda: DMA disabled
hda: WDC AC32500H, 2441MB w/128kB Cache, CHS=620/128/63

Kdyz se ale zeptam na parametry disku:

 Model=WDC AC32500H, FwRev=24.09P07, SerialNo=WD-WT334
 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs
FmtGapReq }
 RawCHS=4960/16/63, TrkSize=57600, SectSize=600, ECCbytes=22
 BuffType=3(DualPortCache), BuffSize=128kB, MaxMultSect=16, MultSect=off
 DblWordIO=no, maxPIO=2(fast), DMA=yes, maxDMA=0(slow)
 CurCHS=620/128/63, CurSects=4999680, LBA=yes, LBAsects=4999680
 tDMA={min:120,rec:120}, DMA modes: mword0 mword1 *mword2 
 IORDY=on/off, tPIO={min:160,w/IORDY:120}, PIO modes: mode3 mode4 

tak je tam hvezdicka u DMA2

Normalne ukazuje hdparm:
 Timing buffered disk reads:  32 MB in  7.40 seconds = 4.32 MB/sec

po hdparm -d 1 se to zlepsi:
Timing buffered disk reads:  32 MB in  4.58 seconds = 6.99 MB/sec

V BIOSu jsem zkouse nastavit i zrusit block-mode, nema vliv, PIO se da
nastavit 0/1/2/3/4/Auto, mam auto, UDMA lze Disabled/Auto, mam auto, DMA
tam ale neni.

Ted otazka - proc Linux vypina DMA? Kdyz ho rucne zapnu, system funguje
(zdanlive) bez nejmensich problemu. Je to ale skutecne bezpecne? Da se
driveru rict rovnou, ze ma pouzit DMA nebo se to musi udelat pres ten
hdparm?

Zdravi

Petr Soucek