linux-kernel - Re: [mmc] incorrect behavior on resume

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Message-ID: <40069.12630.qm@web36708.mail.mud.yahoo.com>
Date:	Sat, 17 Feb 2007 17:46:35 -0800 (PST)
From:	Alex Dubov <oakad@...oo.com>
To:	Pavel Machek <pavel@....cz>, Pierre Ossman <drzeus-mmc@...eus.cx>,
	Greg KH <greg@...ah.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [mmc] incorrect behavior on resume

--- Pavel Machek <pavel@....cz> wrote:

> On Sun 2007-02-18 00:35:33, Pierre Ossman wrote:
> > Alex Dubov wrote:
> > > And today: yet another problem with mmc.
> > > It so happens that after resume mmc layer issues requests to the device before
> mmc_resume_host is
> > > called at all. Moreover, this prevents the machine from resuming, unless worked around,
> because
> > > software timer does not work at this stage of the resume and interrupts may not be delivered
> (if
> > > card was removed, for example).
> > 
> > Now this sounds incredibly broken. A child device should never be resumed before
> > its parent. Pavel, can you comment?
> 
> No, child devices should not be resumed before their parents. Is it
> true child?
> 
> What bus is mmc on? Timer should be resumed fairly early...?
> 
> Can you confirm that rmmod/insmod of mmc around suspend fixes the issue?
> 
> But this is greg's area.
It sure does - if I'll do "rmmod mmc" I'd be forced to remove my driver as well (symbol
dependency) and the problem will magically disappear.

The problem here is that mmc_block's device is a child of real device (tifm_dev here), so it gets
resumed right after it. However, it correct functioning depends on mmc_core, which must be
manually resumed (mmc_resume_host). Therefore, I think this is purely mmc's problem.

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