On Wed, Apr 06, 2016 at 05:22:25PM +0200, Hans de Goede wrote: > Hi, > > On 06-04-16 16:51, Tom Rini wrote: > >On Mon, Apr 04, 2016 at 08:31:48PM +0200, Hans de Goede wrote: > > > >>v7_maint_dcache_all() does not work reliable when build with gcc6, > >>see: https://bugzilla.redhat.com/show_bug.cgi?id=1318788 > >> > >>While debugging this I learned that v7_maint_dcache_all() is unreliable > >>when build with gcc5 too when it is marked as noinline. > >> > >>This commit fixes the reliability issues by replacing the C-code with > >>the ready to use asm implementation from the kernel. > >> > >>Given that this code when written as C-code clearly is quite fragile > >>(also see the existing comments about the C-code being the way it is > >> to get optimal assembly) and that we have a proven asm alternative, > >>I believe that this is the best solution. > >> > >>Note that we actually already have a copy of the kernel's > >>v7_flush_dcache_all() in arch/arm/mach-uniphier/arm32/lowlevel_init.S. > >> > >>We should replace that implementation with a call to this one, but I'm > >>leaving this up to people with access to actual unifier hw. With this > >>replacement in mind I've kept the original function as is, only renamed > >>it to __v7_flush_dcache_all and v7_flush_dcache_all is a wrapper > >>saving the registered clobbered by the core __v7_flush_dcache_all code > >> > >>Signed-off-by: Hans de Goede <hdego...@redhat.com> > > > >So I was able to talk with a few people and this is the right approach. > >The cache routines we're doing here in C must not in fact be done in C. > >That things work today with some compilers is not by design. This is at > >least a minimally correct thing to do and a more correct thing to do > >would be to leverage more of the code from the kernel for cache > >functions (and not just for v7). > > Thanks! I guess that means that we can consider this issue resolved? > Which is good news as this was a nasty bug to track down.
Yes it was, good job btw. > So are you planning on merging this patch / these 2 patches to > master then ? > > Note that in my testing only the first patch is necessary to fix > various sunxi boards no longer booting. We need at least a v2 to fix the build issue Masahiro pointed out. But yes, I'll tkae these two and put the rest on my TODO list. Thanks! -- Tom
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