linux-kernel - Re: [PATCH 2.6.25-rc6] sata_promise: fix hardreset hotplug quirk

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Date:	Sun, 23 Mar 2008 21:07:30 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Mikael Pettersson <mikpe@...uu.se>
CC:	jeff@...zik.org, kurt@...ckx.be, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.25-rc6] sata_promise: fix hardreset hotplug quirk

Mikael Pettersson wrote:
>  > Actually, this is common to many SATA controllers.  Lots of them raise
>  > PHY event or hotplug interrupt during COMRESET and they all plug PHY
>  > events from ->freeze.
> 
> Hmm, no I didn't know that. It's still undocumented, but perhaps
> shouldn't be called a "quirk" if it's as common as you say.

Yeap, it's common behavior.  "quirk" would be a bit unfair to promise. :-)

>  > > Although SATA hotplug status and control is per-port, it resides in
>  > > a single register shared by all ports. Therefore accesses to it must
>  > > be serialised: the controller's host->lock is used for that. The
>  > > interrupt handler is also adjusted so its hotplug register accesses
>  > > are inside the region protected by host->lock.
>  > 
>  > Hmmm... This is supposed to be handled by setting ap->lock appropriately
>  > and ap->lock already is initialized to &host->lock, so sticking with
>  > ap->lock is the right thing to do.
> 
> I'll check this. The code relies on the lock being shared by all ports,
> so at a minimum it will need a comment stating that requirement.

That's the default assumption all other LLDs depend on.  I agree it
needs documentation.

>  > ->freeze() is called with ap->lock held, trying to lock host->lock
>  > inside pdc_sata_enable/disable_hotplug() will result in deadlock.  Have
>  > you tested w/ SMP configuration or spinlock debugging turned on?
> 
> No, I'll do that and fix whatever damage occurs.

Thanks.

-- 
tejun
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