Re: [PATCH-RFC] Promise SATA300 TX4

[Alexander Sabourenkov <screwdriver@lxnt.info>]

Hello.

> Interesting, but can you please give more background information?
> I.e., how did you determine the existence of this bug?

I was experiencing read/write errors, with data corruption.
Dmesgs and lspcis are at http://lxnt.info/linux/

I downloaded driver from the promise.com, put up 2.6.11 and compiled it.
It worked ok.

I then unsuccessfully tried to port the driver to 2.6.22.
While I failed, this gave me enough insights into ATA workings, that I
could read the CAM module that comes with the driver.

Looking through it I found the SG_COUNT_ASIC_BUG constant and
corresponding code. I decided to try and implement the workaround in
sata_promise.c - and this fixed the problem.

> And please cc: the sata_promise maintainer on sata_promise patches.
> (Hint: that's me)

Hmm. sata_promise.c says:

*  Maintained by:  Jeff Garzik <jgarzik@pobox.com>

> Meanwhile I'll check the Promise driver(s) to see if there's
> something about SG table formatting restrictions there.

Take a look at:

cam_ata.c:6190
cam_ata.c:6259

The fix is also conditioned on sg segment length == 0, which I did not
implement. Is this at all possible in libata ?

-- 

./lxnt