On Fri, Apr 28, 2006 at 07:53:29AM +1000, Benjamin Herrenschmidt wrote: > > > There are many mv64x60 based platforms working just fine today with > > CONFIG_NOT_COHERENT_CACHE defined. The reason for turning coherency off > > is that there is a bug in the bridge requiring a hardware workaround. > > Unfortunately, not all of the hardware vendors have implemented that > > workaround and I know of one that considers it infeasible and will > > not implement it. > > Define "working fine" ... With the current implementation, and according > to the spec, it will randomly crap out or checkstop due to the same page > beging accessed via the NCU and being in the L2 unless you disabled > speculative loads and made sure it can't prefetch accross page > boundaries maybe ? Or set the G bit all over the BAT mapping (ouch !).
"working fine" == running in a production environment for weeks/months without crapping out. > > If that hardware workaround is not implemented, the options are: > > a) 100% chance of a system hang with coherency on > > or > > b) < 0.0..1% chance of a system hang with coherency off (at least in my > > experience to far). > > > > The choice is simple. > > I disagree. A solution that is known to have a hole in it is no good > even if you haven't managed to trigger it so far. Now it's Gerhard's > choice. TBH, I haven't really looked at what Gerhard is doing yet so I can't comment. No matter what, though, its certainly his choice. Mark -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
