[9fans] Bug Report. Maybe DMA race on Abit BX6

[9fans] Bug Report. Maybe DMA race on Abit BX6

[Carl-Johan Kjellander]

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Plan 9 seems to have trouble installing on Abit BX6 motherboards.
I've tried installing it on two Abit BX6 motherboards but the installations
always fails at the same place.

When doing mountfs and answering wipe plan 9 starts to wipe the partitions.
After 5-10 seconds the load goes up to max and nothing more happens.

I can run Plan 9 fine from the install cd and I've had it up for more than
a week, but I can't get it installed on the harddisk.

The chipset on the motherboard is Intel 82371AB (PIIX4) so it should be
supported, and maybe the DMA is to blame? Maybe a race condition.

Anyway, is it possible to force the kernel not to use DMA when booting?
Or is there another kernel I could try to get it installed.

please CC me since I'm not on the list.
/Carl-Johan Kjellander
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Re: [9fans] Bug Report. Maybe DMA race on Abit BX6

[andrey mirtchovski]

On Wed, 20 Aug 2003, Carl-Johan Kjellander wrote:

> Anyway, is it possible to force the kernel not to use DMA when booting?
> Or is there another kernel I could try to get it installed.
>

you can configure the machine not to use DMA from the BIOS. also try 'cat
/dev/sdC0/ctl' to see whether it's on or off.

doing a 'echo dma off > /dev/sdC0/ctl' will disable dma

that assumes your disk is under /dev/sdC0 :)

andrey

[9fans] Bug Report. Maybe DMA race on Abit BX6

[Carl-Johan Kjellander]

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andrey mirtchovski wrote:
 > On Wed, 20 Aug 2003, Carl-Johan Kjellander wrote:
 >
 >  > Anyway, is it possible to force the kernel not to use DMA when booting?
 >  > Or is there another kernel I could try to get it installed.
 >  >
 >
 > you can configure the machine not to use DMA from the BIOS. also try 'cat
 > /dev/sdC0/ctl' to see whether it's on or off.
 >
 > doing a 'echo dma off > /dev/sdC0/ctl' will disable dma
 >
 > that assumes your disk is under /dev/sdC0 :)

Thanks! Getting another rc window up and turning off dma did the trick!
After that everything installed fine.

So there is a bug in the dma-handling for the Abit BX6 motherboard.

Please CC me
/Carl-Johan Kjellander
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Re: [9fans] Bug Report. Maybe DMA race on Abit BX6

[andrey mirtchovski]

On Wed, 20 Aug 2003, Carl-Johan Kjellander wrote:

> So there is a bug in the dma-handling for the Abit BX6 motherboard.
>

according to jmk, if there was a bug in the dma code, data corruption
would be the most likely effect. however i've suffered only from race
conditions in fossil with dma on

andrey

Re: [9fans] Bug Report. Maybe DMA race on Abit BX6

[jmk]

On Wed Aug 20 14:53:28 EDT 2003, mirtchov@cpsc.ucalgary.ca wrote:
> On Wed, 20 Aug 2003, Carl-Johan Kjellander wrote:
>
> > So there is a bug in the dma-handling for the Abit BX6 motherboard.
> >
>
> according to jmk, if there was a bug in the dma code, data corruption
> would be the most likely effect. however i've suffered only from race
> conditions in fossil with dma on
>
> andrey

The manifestation of DMA not being properly set up can range from
subtle data corruption to system hangs. The problem is almost always
caused by the BIOS setting the drive to a different DMA mode than
that set in the controller-dependent registers. Plan 9 currently
assumes the BIOS doesn't make that mistake, and that is why DMA
should never be enabled unless you are sure it will work OK. The
driver should someday be able to do this check and configure the
hardware correctly.