On 2007.01.18 18:09:50 -0600, Robert Hancock wrote:
> I heard from Larry Walton who was apparently seeing this problem as
> well. He tried my recent "sata_nv: cleanup ADMA error handling v2" patch
> and originally thought it fixed the problem, but it turned out to only
> make it happen less often.
>
> I wouldn't expect that patch to have an effect on this problem. If it
> seems to reduce the frequency that would tend to be further evidence of
> some kind of timing-related issue where the code change just happens
> to make a difference.
>
> I'll see if I can come up with a debug patch for people having this
> problem to try, which prints out when a flush command is issued and what
> interrupts happen when a flush is pending.
>
> There is one important difference between ADMA and non-ADMA mode for
> non-DMA commands like flushes, which didn't come to mind before: ADMA
> mode uses MMIO registers on the controller whereas non-ADMA mode uses
> legacy IO registers. Posted write flushing is a concern with MMIO
> registers but not with PIO, the libata core is supposed to handle this
> but maybe it doesn't in some case(s). In fact, just looking at
> libata-sff.c there's this comment on the ata_exec_command_mmio function:
>
> * FIXME: missing write posting for 400nS delay enforcement
>
> That seems a bit suspicious..
That would imply that disabling adma via a module parameter should make
the issue go away, right? I'll try to have a test run with adma disabled
over night then.
Thanks,
Björn
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