Date: Tue, 24 May 2016 15:59:16 -0600 From: Ian Lepore <ian@freebsd.org> To: Mark Millard <markmi@dsl-only.net>, freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: xorg broken on Beaglebone black revision 300438 Message-ID: <1464127156.1204.10.camel@freebsd.org> In-Reply-To: <AE62E2F1-1D9F-418F-97E8-6D7F0E6B4B87@dsl-only.net> References: <AE62E2F1-1D9F-418F-97E8-6D7F0E6B4B87@dsl-only.net>
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On Tue, 2016-05-24 at 14:35 -0700, Mark Millard wrote: > Quoting from Otacílio Tue May 24 00:06:10 UTC 2016 and its locore > -v6.S changes: > > > - orr r7, #CPU_CONTROL_UNAL_ENABLE > > - orr r7, #CPU_CONTROL_AFLT_ENABLE > > + bic r7, #CPU_CONTROL_UNAL_ENABLE > > + bic r7, #CPU_CONTROL_AFLT_ENABLE > > -r295256 (2016-Feb-14) changed from: > > bic r7, #CPU_CONTROL_UNAL_ENABLE > > to: > > orr r7, #CPU_CONTROL_UNAL_ENABLE > > in two places (moving it a few lines down for each example as well). > So this much of the proposed changes would be reverting the -r295256 > change. The check in comment indicates the bit is RAO/SBOP for armv7. > For armv6 the check in comment claims it controls armv5 compatible > alignment support. > > But: > > orr r7, #CPU_CONTROL_AFLT_ENABLE > > has been in locore-v6.S since the file's first checkin. So this > change to bic here be new. > > What is the FreeBSD intent for each of the two new settings for > armv7? armv6? > It was always wrong to clear CPU_CONTROL_UNAL_ENABLE on armv7 (it's documented as RAO/SBOP). Setting it on armv6 makes the v6 (which is only the RPi in our world) behave the same as v7. So that change was just a bugfix. I think FreeBSD is the only major OS left that is enforcing strict alignment on armv6/v7 and it causes a lot of trouble for ports and other 3rd party software, and prevents us from enabling certain compiler options and optimizations. I'm very close to a commit to stop enforcing strict alignment (clear rather than CPU_CONTROL_AFLT_ENABLE). I've been testing it yesterday and today, and haven't run into any trouble at all. -- Ian
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