On Tue, Jun 02, 2015 at 11:08:35AM +0100, Paul Burton wrote: > Hi Leonid, > <snip> > > + > > + If that instructions are not implemented in processor then it is > > + converted to generic "SYNC 0". > > I think this would read better as something like: > > If a processor does not implement the lightweight sync operations then > the architecture requires that they interpret the corresponding sync > instructions as the typical heavyweight "sync 0". Therefore this > should be safe to enable on all CPUs implementing release 2 or > later of the MIPS architecture. > Is it really the case for release 2? I'm asking because recently I needed to do something similar and I couldn't find this garantee in the revision 2.00 of the manual. May it's just poorly formulated but here is what I find in it: - "The stype values 1-31 are reserved for future extensions to the architecture." (ok) - "A value of zero will always be defined such that it performs all defined synchronization operations." (ok) - "Non-zero values may be defined to remove some synchronization operations." (ok, certainly if we understand the word "weaker" instead of "remove") - "As such, software should never use a non-zero value of the stype field, as this may inadvertently cause future failures if non-zero values remove synchronization operations." (Mmmm, ok but ...) Nowhere is there something close to what is found in the revision 5.0 or later: "If an implementation does not use one of these non-zero values to define a different synchronization behavior, then that non-zero value of stype must act the same as stype zero completion barrier." The wording may have changed since revision 2.8 but I don't have access to the corresponding manual. Luc Van Oostenryck
