Re: DMA disabled

[Florian Kulzer <florian@molphys.leidenuniv.nl>]

Sumith augustine wrote:
> Hello Everybody,
>
> I am using a Sarge sys with Kernel 2.6.8-2-686 and Radi-1 (hda/hdc)
> Every day at boot time  am getting a DMA time out error for harddisk hdc,
> it  says DMA is disabled. At the same time there is no problem with the hda.
> The syslog msgs are given below.
>
> Mar 22 13:43:52 localhost kernel: hdc: ST340810A, ATA DISK drive
> Mar 22 13:43:52 localhost kernel: hdc: set_drive_speed_status: status=0xd0 {
> Busy }
> Mar 22 13:43:52 localhost kernel: ide1 at 0x170-0x177,0x376 on irq 15
> Mar 22 13:43:52 localhost kernel: hdc: max request size: 128KiB
> Mar 22 13:43:52 localhost kernel: hdc: status timeout: status=0xd0 { Busy }
> Mar 22 13:43:52 localhost kernel:
> Mar 22 13:43:52 localhost kernel: hdc: drive not ready for command
> Mar 22 13:43:52 localhost kernel: hdc: 78165360 sectors (40020 MB) w/2048KiB
> Cache, CHS=65535/16/63, UDMA(33)
> Mar 22 13:43:52 localhost kernel:  /dev/ide/host0/bus1/target0/lun0:hdc:
> status timeout: status=0xd0 { Busy }
> Mar 22 13:43:52 localhost kernel:
> Mar 22 13:43:52 localhost kernel: hdc: DMA disabled
> Mar 22 13:43:52 localhost kernel: hdd: DMA disabled
> Mar 22 13:43:52 localhost kernel: hdc: drive not ready for command
> Mar 22 13:43:52 localhost kernel: ide1: reset: success
> Mar 22 13:43:52 localhost kernel:  p1 p2 p3 p4 < p5 p6 p7 p8 p9 >
>
>  the hdparm results for hdc is
>
> /dev/hdc:
>  multcount    =  0 (off)
>  IO_support   =  0 (default 16-bit)
>  unmaskirq    =  0 (off)
>  using_dma    =  0 (off)
>  keepsettings =  0 (off)
>  readonly     =  0 (off)
>  readahead    = 256 (on)
>  geometry     = 65535/16/63, sectors = 78165360, start = 0
>
> > From this i understand that the dma is off,  Should i enable the DMA using
> "hdparm -d1 /dev/hdc or should i do somthing else ?
>
> Is it safe to use hdparm? and ll it cause any data lose?
> Or should i do somthing to solve this DMA problem?

If you want to play it safe you could boot from a Knoppix CD. Then the
HDs are mounted read-only and you can check if Knoppix manages to enable
DMA for hdc.

The errors during boot in your install seem to indicate that the system
tries to enable DMA for hdc and fails. Therefore I would expect that you
will simply get an error message if you attempt to activate it later
with hdparm. You could try this carefully in single user mode with the
drive mounted read-only.

The failure to turn on DMA during boot could be due to a missing module
in your initrd or due to modules being loaded in the wrong order. It
might even be that you have very new hardware which is not fully
supported in kernel 2.6.8. It would help if you posted the output of
"lspci" here, so that we can know the exact model and revision of your
controller.

Regards,
           Florian