linux-kernel - Re: ahci_start_engine compliance with AHCI spec

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Date:	Mon, 18 Jul 2011 11:40:17 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-ide@...r.kernel.org, Valdis.Kletnieks@...edu,
	"Rafael J. Wysocki" <rjw@...k.pl>, Jeff Garzik <jgarzik@...ox.com>,
	Michael Leun <lkml20100708@...ton.leun.net>,
	linux-kernel@...r.kernel.org, Jian Peng <jipeng2005@...il.com>,
	Kevin Cernekee <cernekee@...il.com>
Subject: Re: ahci_start_engine compliance with AHCI spec

Hi Tejun,

On Wed, Jul 13, 2011 at 6:14 AM, Tejun Heo <tj@...nel.org> wrote:
> On Fri, Jul 08, 2011 at 04:01:17PM -0700, Brian Norris wrote:
>> I'm not sure if the "error_handler" and "hard reset" processes are
>> intended for initialization...as I said I'm a little new!
>
> That's how it's supposed to work.  EH is integral part of probing
> sequence.

I began to suspect that was the case. It just seemed awkward that the
expected operation includes a code path named "error".

>> I have a few other questions:
>>
>> What operation could be putting devices in DRQ or BSY states during
>> initialization but before ahci_start_engine?
>
> Hmmm... I have no idea, maybe it has something to do with the first
> D2H Reg FIS device sends after link gets reset during controller init?

OK, I'll try to track that one down, but I think that DRQ is set much
earlier in the initialization than that and won't be cleared until
between ahci_power_up() and ahci_start_engine() - I tried
wait-and-poll at several different points in the process to understand
the HBA/device initialization process.

> Hmmm... what happens if you don't comment out ahci_start_engine() call
> from ahci_start_port()?

I wasn't commenting out the ahci_start_engine() from
ahci_start_port(). Can you clarify what you mean?

> Is this the same IP block that Jian Peng was using?

Yes, it is. I'm taking over some of his work.

Thanks for the responses.

Brian
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