From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philippe De Muyter Subject: Re: [PATCH] m68knommu: allow ColdFire CPUs to use unaligned accesses Date: Fri, 8 Jun 2012 15:35:03 +0200 Message-ID: <20120608133503.GA12617@frolo.macqel> References: <1339134180-13630-1-git-send-email-gerg@snapgear.com> <20120608103931.GA26964@frolo.macqel> <4FD1EDDF.1040101@snapgear.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mailrelay004.isp.belgacom.be ([195.238.6.170]:21003 "EHLO mailrelay004.isp.belgacom.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590Ab2FHNfH (ORCPT ); Fri, 8 Jun 2012 09:35:07 -0400 Content-Disposition: inline In-Reply-To: <4FD1EDDF.1040101@snapgear.com> Sender: linux-m68k-owner@vger.kernel.org List-Id: linux-m68k@vger.kernel.org To: Greg Ungerer Cc: linux-m68k@vger.kernel.org, uclinux-dev@uclinux.org, Greg Ungerer Hi Greg, On Fri, Jun 08, 2012 at 10:19:43PM +1000, Greg Ungerer wrote: > Hi Philippe, > > On 06/08/2012 08:39 PM, Philippe De Muyter wrote: >> On Fri, Jun 08, 2012 at 03:43:00PM +1000, gerg@snapgear.com wrote: >>> From: Greg Ungerer >>> >>> All current ColdFire CPUs are able to support unaligned memory acce= sses. >>> So remove the CONFIG_CPU_HAS_NO_UNALIGNED option selection for Cold= =46ire. >>> >>> It seems that the current restriction was inherrited from the early= =20 >>> non-MMU >>> support for the basic 68000 proecssors - which do not support unali= gned >>> accesses. >> >> It seems that the first ColdFires needed the restriction : >> >> I read in the "MCF5200 ColdFire Family Programmer=C3=83=E2=80=A0s Re= ference Manual"=20 >> : >> >> The ColdFire processor default configuration supports word- and >> longword-sized operand references on 0-modulo-2 and 0-modulo-4 >> addresses, respectively. All other references are defined as >> misaligned accesses. Any attempt to access a misaligned operand >> generates an address-error exception, unless the optional hardware >> module for handling misalignment is present. This misalignment >> module converts any misaligned operand references into a series >> of aligned bus cycles to access the data. The existence of the >> misalignment module is implementation-dependent and is documented >> in the appropriate ColdFire user=C3=83=E2=80=A0s manual. I mentionned that only to make you able to soften the commit comment :) > > I wish Freescale really did make that clear within the doco for each > part! > > The oldest (and I assume simplest) part we support is the 5206, and i= t > does explicitly state in the MCF5206UM that it supports unaligned > accesses (Section 6.6). It is not as clear as this in some of the > other CPU/SoC User Manuals that I looked through. > > I am pretty confident that all the parts we currently support in Linu= x > do unaligned accesses. I agree. And if some parts did not implement it, we'd see it quickly. Regards Philippe