Messages in this thread | | | Date | Sat, 10 May 2008 15:34:11 +0900 | From | Tejun Heo <> | Subject | Re: [PATCH] Re: [git patches] libata updates - (improve post-reset device ready test) regression |
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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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