On Thu, Oct 29, 2009 at 10:00:28AM +0100, Joakim Tjernlund wrote: > > I have found the problem. It occurred to me in the shower (okay not really, > > but most good ideas happen there). > > > > What was happening is that I was in fact able to write to the correct > > registers. However, I would try and write to them in a batch. But the way > > mmap works (at least according to the man page) with MAP_SHARED is that the > > file may not be updated until msync() is called. Now, I thought that O_SYNC > > would take care of that when I open /dev/mem, but that was not the case. > > > > Anyway, to make a long story short, I inserted an msync() after each > > assignment to the flash. This resolved my problem and I can now program my > > flash. > > Ouch, this was news to me too. Calling msync() after every write kills > performance. > We use mmap(/dev/mem) to access HW and havn't seen any issues yet. Is this > perhaps a new behaviour for mmap(/dev/mem) and is there a way > to avoid calling msync()?
I suspect that the msync() was merely serving as a very heavyweight memory barrier. -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
