From: "Eric Bénard" <eric@eukrea.com>
To: barebox@lists.infradead.org
Subject: Re: [PATCH] usb: fix unaligned access
Date: Mon, 24 Oct 2011 21:02:53 +0200 [thread overview]
Message-ID: <4EA5B65D.4020405@eukrea.com> (raw)
In-Reply-To: <CAJeSw6CfdF5UuN0fk=trKi-bJD009yDcasjkp_f2twR9giRaCw@mail.gmail.com>
Hi,
Le 24/10/2011 20:37, Fabian van der Werf a écrit :
>
> Okay, I think it may be a compiler problem. The latest code sourcery
> compiler builds a barebox that breaks on usb. 2009q1-203 builds fine,
> however.
>
> In the usb code the compiler should be able to figure out that the
> access is unaligned from the packed structure. So I guess it should
> split up the access in multiple loads/stores. I will look into the
> binaries to confirm this. The latest compiler may be broken or maybe
> the default behaviour has changed because armv7 actually supports
> unaligned access.
>
can't this be the same problem described here with gcc 4.6 :
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/791552
solved by this patch :
https://launchpadlibrarian.net/73908303/0001-USB-ehci-remove-structure-packing-from-ehci_def.patch
with the following explanation :
The kernel source marks ehci_regs as packed. gcc 4.6 treats all accesses to
packed structures as unaligned and ends up reading the status register
multiple times.
Eric
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next prev parent reply other threads:[~2011-10-24 19:03 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-22 13:19 [PATCH] usb: fix unaligned access Fabian van der Werf
2011-10-22 20:20 ` Sascha Hauer
2011-10-23 9:29 ` Fabian van der Werf
2011-10-24 15:14 ` Antony Pavlov
2011-10-24 17:07 ` Sascha Hauer
2011-10-24 18:37 ` Fabian van der Werf
2011-10-24 19:02 ` Eric Bénard [this message]
2011-10-24 19:30 ` Sascha Hauer
2011-10-24 19:42 ` Eric Bénard
2011-10-25 18:36 ` Fabian van der Werf
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