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SubjectSecond Thought (Re: Re[2]: Small error?? in IDE dma processing?)

First lets run some system crashes...........(which I did)....even worse!!
Then look at the ATA/ATAPI-4 spec T13-1153D Revision 17 30-Oct-97 page 234,
again. The flow charts on DMA procedure to my reading again (not late at
night in a dimly lit room at 1am).
Both branches of the test 0IEN=0 :

At test DEVICE: nIEN=0 ?

No -> Host : Read of Status register is recommended.
NOTE : Status register is read to clear pending interrupt.
END

Yes -> Device : Assert INTRQ
Host : Read Status register
Device : Negate INTRQ
END


wait for device to issue interrupt request
then first read the status ***
then clear the interrupt

***
It is not all clear if this is refering to DMA or Drive Status; however,
it is reasonable to assume that it is DMA first.

Like the original code.

A closer look at 29055002.pdf (intel), 29765804.pdf (intel),
d1153r17.pdf, and some source code on loan from HighPoint Tech.
(a public branch of Triton).

I now think the original code is correct.
Note that I will test this question more objectively on a drive that
doesn't have some non-correctable error accounting.
(forgot to bad block check and mark the drive first, duh....)
Have you switched the code and tested it youself yet?

On Wed, 16 Dec 1998 jason.harp@mail.ray.ca wrote:

>
> Will you make the appropriate changes to 2.0 and 2.1 IDE code?
>

If this is the correct solution, yes. I am now not convinced that it is
the correct answer. The follow up docs on the PIIX/PIIX3 have a DMA
BusMaster bit order corrections, also.

Cheers,
Andre Hedrick
The IDE-FNG for Linux
The APC UPS Specialist for Linux

http://www.dyer.vanderbilt.edu/server/udma/
http://www.dyer.vanderbilt.edu/server/apcupsd/apcupsd-3.5.2.bin.tar.gz










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