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SubjectRe: [PATCH] Re: [git patches] libata updates - (improve post-reset device ready test) regression
Jeff Garzik wrote:
> Tejun Heo wrote:
>> This means that we need to make custom readiness tests for controllers
>> using 0x77 or 0x7f. Eeeek... Both groups of controllers are behaving
>> in incorrect way. Controllers shouldn't use 0x77 or 0x7f for either
>> busy or ready states - it's invalid for both, yet, some use the 77/7f
>> for busy while others use them for ready state. Great. :-(
>
> I think that's assuming too much? PATA and SATA are quite different
> here... in PATA the status is mostly the value from the device directly
> off the wires. in SATA, it may be from the device or from the
> controller. And "smart" or firmware-based controllers may generate
> their own status, too, apart from the device's status.
>
> So that results in varied status returns, and not all the time is a
> definite "ready" or "not ready" obvious.

I think it's pretty safe to say that these weird ready values are from
TF emulation on controller side. The ready/not ready distinction is
probably too simplistic but those values aren't supposed to appear
during post-reset readiness test.

Sorry about the big regression. Heh... It's amazing how all the
controllers I tested didn't show the problem and I did test a good
number of combinations.

I still think it would be better to have a unified readiness test
function. The problem is subtle (device misdetection on hotplug of
certain drives) and went unnoticed quite some time for JMB ahcis && test
coverage over those things can't be good. I'll try to think about
something better.

Thanks.

--
tejun


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