MPC8xx IDMA and console garbage

Thomas Lange thomas at
Tue Apr 23 21:51:32 EST 2002

I also played around with IDMA and noticed the
same thing.

Serial works ok if you put idma priority below
SMC priority. Never investigated further...


Steven Scholz wrote:
> Hi there,
> I am trying to get DMA support for MPC8xx IDE. For now I use the IDMA
> channel.
> It is kind of working although it's not much more than a framework yet.
> BUT:
> My problem right now is this:
> After activating the DMA (e.g. using hdparm -d1 /dev/hda) the output of
> my serial console (connected to SMC1) gets garbaged when there is HDD
> activity.
> If I telnet into my machine and do e.g. a "fdisk -l /dev/hda" the output
> of the serial console looks something like this
> ^PttyS: 80 input overrun(s)
>  ^P^P^P^P^P^P^P^P^P^ ^PP ^ ^PP ^ ^PP ^P ^P^P^P^P^P^P ^P
> ^P^P^P^P^P^P^P^P^P^P^P^P^PttyS: 80 input overrun(s)
> If I redirect console input into a file it contains 0x10 and 0x20 bytes.
> So someone is flooding the serial port (SMC) with the two byte 0x10 and
> 0x20 !
> (I might have seen 0x10 and 0xA0 as well.)
> Any ideas?
> Could there be a problem in using the internal ram area. Maybe my IDMA
> is conflicting with anyother existing driver (SMC???) ?
> Thanks,
> Steven

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