From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Date: Tue, 5 May 2015 10:39:14 +0100 Subject: [U-Boot] [PATCH] sunxi: display: Align end of memory to work around a linux-4.0 bug In-Reply-To: <1430732203.15640.220.camel@hellion.org.uk> References: <1429900783-15152-1-git-send-email-hdegoede@redhat.com> <1430572906.15640.93.camel@hellion.org.uk> <55473315.3020508@redhat.com> <1430732203.15640.220.camel@hellion.org.uk> Message-ID: <20150505093914.GA20402@leverpostej> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Mon, May 04, 2015 at 10:36:43AM +0100, Ian Campbell wrote: > On Mon, 2015-05-04 at 10:51 +0200, Hans de Goede wrote: > > Hi, > > > > On 02-05-15 15:21, Ian Campbell wrote: > > > On Fri, 2015-04-24 at 20:39 +0200, Hans de Goede wrote: > > >> Linux-4.0 as shipped has a bug causing it to not boot if the end of memory > > >> is not aligned to a multiple of 2 MiB. For details see the linux-arm > > >> mailing list post titled: > > >> "Memory size unaligned to section boundary" > > >> http://www.spinics.net/lists/arm-kernel/msg413811.html > > >> > > >> This is something which specifically hits the sunxi display driver because > > >> we carve out the exact needed framebuffer size at the top of mem, this > > >> commit works around this issue by aligning the carve out. > > > > > > I'm afraid I don't like this, we shouldn't be working around Linux bugs > > > in the firmware, especially when both are Free software. Lets just fix > > > Linux and get the fix into the appropriate stable trees and in the > > > meantime tell people to avoid this buggy kernel. > > > > > > The problem with this sort of thing is that it is very hard to get rid > > > of these workarounds, even once the underlying issue is fixed and we no > > > longer care about the versions with the bug OS authors (including > > > non-Linux OSes) can inadvertently come to rely on the quirky behaviour, > > > (i.e. the work around masks other bugs). Hence we end up in a > > > quirks-race as everyone works around the other parties last workaround. > > > > > > If there is to be a workaround instead of a fix then it should be for > > > Linux to align memory to 2MB boundaries if that is what it requires. > > > > I can understand where you're coming from, the problem is that despite > > various mails to the arm kernel mailing list no one from the upstream > > kernel seems to be looking into this, > > Mark, do you think you could find some cycles (not necessarily your own) > to look at this, or perhaps you know the appropriate maintainers to > ping? I'll have another look and see if I can come up with a kernel patch. Perhaps proposing something (even if slightly wrong) will provoke people to respond. > I'd really like to avoid having to hack around kernel bugs in the > firmware. Likewise. Mark.