From: "Måns Rullgård" <mans@mansr.com>
To: Greg KH <gregkh@suse.de>
Cc: "Mikael Pettersson" <mikpe@it.uu.se>,
"Måns Rullgård" <mans@mansr.com>,
"Nicolas Pitre" <nico@fluxnic.net>,
linux-usb@vger.kernel.org, "Harro Haan" <hrhaan@gmail.com>,
linux-kernel@vger.kernel.org,
"Alan Stern" <stern@rowland.harvard.edu>,
"Lennert Buytenhek" <kernel@wantstofly.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] fix ehci alignment error
Date: Mon, 10 Oct 2011 19:41:55 +0100 [thread overview]
Message-ID: <yw1x4nzgzo24.fsf@unicorn.mansr.com> (raw)
In-Reply-To: <20111010173845.GB25114@suse.de> (Greg KH's message of "Mon, 10 Oct 2011 10:38:45 -0700")
Greg KH <gregkh@suse.de> writes:
> On Mon, Oct 10, 2011 at 07:31:26PM +0200, Mikael Pettersson wrote:
>> Greg KH writes:
>> > On Mon, Oct 10, 2011 at 05:29:13PM +0100, Måns Rullgård wrote:
>> > > Greg KH <gregkh@suse.de> writes:
>> > >
>> > > > On Mon, Oct 10, 2011 at 02:38:27PM +0200, Harro Haan wrote:
>> > > >> The Kirkwood gave an unaligned memory access error on
>> > > >> line 742 of drivers/usb/host/echi-hcd.c:
>> > > >> "ehci->last_periodic_enable = ktime_get_real();"
>> > > >
>> > > > What is "The Kirkwood"? What size processor is this?
>> > >
>> > > It's an ARM926-like CPU from Marvell.
>> >
>> > 32 or 64bit?
>>
>> All ARMs are 32-bit, but some have instructions for loading or
>> storing 2 x 32 bits at a time, but also require the corresponding
>> memory address to be 64-bit aligned.
To be perfectly accurate, all ARMs have the dual load/store instructions,
but only some (ARMv5 and earlier) require a 64-bit aligned address for
these. The Kirkwood is an ARMv5 so it does need this alignment.
Furthermore, the standard ARM ABI requires 8-byte alignment for 64-bit
data types regardless of CPU version, which is perhaps a bit unusual for
a 32-bit architecture.
--
Måns Rullgård
mans@mansr.com
next prev parent reply other threads:[~2011-10-10 18:41 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-10 12:38 [PATCH] fix ehci alignment error Harro Haan
2011-10-10 14:14 ` Greg KH
2011-10-10 16:29 ` Måns Rullgård
2011-10-10 17:00 ` Greg KH
2011-10-10 17:31 ` Mikael Pettersson
2011-10-10 17:38 ` Greg KH
2011-10-10 18:41 ` Måns Rullgård [this message]
2011-10-10 15:28 ` Alan Stern
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