linux-kernel - Re: [PATCH] MMC: Add 400ms to CAFE SD controller resume path

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Message-Id: <20090528013629.0173522b.akpm@linux-foundation.org>
Date:	Thu, 28 May 2009 01:36:29 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pierre Ossman <pierre@...man.eu>
Cc:	dsaxena@...xity.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MMC: Add 400ms to CAFE SD controller resume path

On Fri, 22 May 2009 13:51:50 +0200 Pierre Ossman <pierre@...man.eu> wrote:

> On Wed, 13 May 2009 20:05:56 +0000
> Deepak Saxena <dsaxena@...xity.net> wrote:
> 
> > 
> > The CAFE SD controller takes a long time to completely resume
> > and w/o this patch, we do not redetect an existing card but
> > instead detect it as a new one. Even with MMC_UNSAFE_RESUME
> > enabled, this leads to the partition table on the device being
> > wiped out.
> >     
> > See http://dev.laptop.org/ticket/6532 for gory details.

hm, this sounds like a fairly serious problem, but the patch is nearly
a year old.

> > Signed-off-by: Deepak Saxena <dsaxena@...top.org>
> > 
> 
> Reading through that report, I don't believe you properly worked around
> the bug. You only avoid bug 1339, but that's only mildly related.
> 
> What this workaround does is to make sure that MMC_UNSAFE_RESUME
> actually works. But if you change cards during suspend, the VFS bug
> should reappear and you'll corrupt the partition table.

What do you think the VFS did wrong here?

> And as for 1339, has there been any more work done on why this problem
> doesn't appear in OFW? I'd be a lot happier if we could make things
> work without artificial delays.


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