linux-kernel - Re: [RFC 3/3] libata: don't perform HW activity in devres

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Message-ID: <CAN8TOE_DThBeGvHN9HQtX3CDLuiWDJEVZNKFqRnnOmP=xHN8XQ@mail.gmail.com>
Date:	Thu, 25 Oct 2012 10:41:57 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Jeff Garzik <jgarzik@...ox.com>, linux-ide@...r.kernel.org,
	linux-pm@...ts.linux-foundation.org,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Kevin Cernekee <cernekee@...il.com>
Subject: Re: [RFC 3/3] libata: don't perform HW activity in devres

On Thu, Oct 25, 2012 at 10:25 AM, Tejun Heo <tj@...nel.org> wrote:
> On Thu, Oct 25, 2012 at 09:56:01AM -0700, Brian Norris wrote:
>> devres functions are intended for simplified cleanup of memory and other
>> software resources on device exit, not for hardware shutdown sequences.
>> In addition, inducing hardware activity at device removal hamstrings
>> some drivers (particularly ahci_platform) so that they cannot totally
>> power off their hardware before removal, as devres cleanup occurs after
>> the driver's exit() sequence.
>>
>> More concretely, I experience the following bus error when using rmmod
>> to remove (and power off) the SATA block on my SoC:
>
> Shouldn't poweroff happen from ->port/host_stop()?

Hmm, I guess that makes more sense. I was using the ahci_platform
ahci_platform_data->exit() function. Would it be safe to call the
platform init()/exit() functions as part of a
ata_port_operations.host_{start,stop}() hook? These functions aren't
currently implemented at all in ahci_platform, but I don't see why
they couldn't be.

Brian
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