OSB4 issues on 2.4.19-ac4

[Samuel Flory]

  It appears that the OSB4 ide controller isn't working on ac4.  I have
a Tyan 2515, and 2518 which hang when dma is enabled.

The 2518 hangs on a "hdparm -t /dev/hda" after enabling dma:  
Uniform Multi-Platform E-IDE driver Revision: 6.31
ide: Assuming 33MHz system bus speed for PIO modes; override with
idebus=xx
SvrWks OSB4: IDE controller on PCI bus 00 dev 79
SvrWks OSB4: chipset revision 0
SvrWks OSB4: not 100% native mode: will probe irqs later
    ide0: BM-DMA at 0xffa0-0xffa7, BIOS settings: hda:DMA, hdb:pio
    ide1: BM-DMA at 0xffa8-0xffaf, BIOS settings: hdc:DMA, hdd:pio
hda: Maxtor 5T040H4, ATA DISK drive
hdc: Maxtor 5T040H4, ATA DISK drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
ide1 at 0x170-0x177,0x376 on irq 15
hda: host protected area => 1
hda: 80043264 sectors (40982 MB) w/2048KiB Cache, CHS=4982/255/63
hdc: host protected area => 1
hdc: setmax LBA 80043264, native  78125000
hdc: 78125000 sectors (40000 MB) w/2048KiB Cache, CHS=77504/16/63
ide-floppy driver 0.99.newide
Partition check:
 hda: unknown partition table
 hdc: unknown partition table

2515 hangs on a "hdparm -t /dev/hda" after enabling dma:
Uniform Multi-Platform E-IDE driver Revision: 6.31
ide: Assuming 33MHz system bus speed for PIO modes; override with
idebus=xx
PDC20267: IDE controller on PCI bus 00 dev 18
PDC20267: chipset revision 2
PDC20267: not 100% native mode: will probe irqs later
PDC20267: ROM enabled at 0xfeae0000
PDC20267: (U)DMA Burst Bit ENABLED Primary MASTER Mode Secondary MASTER
Mode.
    ide2: BM-DMA at 0xdf00-0xdf07, BIOS settings: hde:pio, hdf:pio
    ide3: BM-DMA at 0xdf08-0xdf0f, BIOS settings: hdg:pio, hdh:pio
SvrWks OSB4: IDE controller on PCI bus 00 dev 79
SvrWks OSB4: chipset revision 0
SvrWks OSB4: not 100% native mode: will probe irqs later
    ide0: BM-DMA at 0xffa0-0xffa7, BIOS settings: hda:DMA, hdb:pio
    ide1: BM-DMA at 0xffa8-0xffaf, BIOS settings: hdc:DMA, hdd:pio
hda: ST320410A, ATA DISK drive
hdc: ST320410A, ATA DISK drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
ide1 at 0x170-0x177,0x376 on irq 15
hda: host protected area => 1
hda: 39102336 sectors (20020 MB) w/2048KiB Cache, CHS=2434/255/63
hdc: host protected area => 1
hdc: 39102336 sectors (20020 MB) w/2048KiB Cache, CHS=38792/16/63
ide-floppy driver 0.99.newide
Partition check:
 hda: hda1 hda2 hda3
 hdc: [PTBL] [2434/255/63] hdc1 hdc2 hdc3