On Mon, Jan 16, 2006 at 03:45:43PM +0000, Martin Michlmayr wrote: > * Peter Horton <pdh@xxxxxxxxxxxxxxxxx> [2005-04-14 19:59]: > > This patch adds detection of broken 64-bit mode LL/SC on Cobalt units. > > With this patch my Qube2700 boots a 64-bit build fine. The later units > > have some problems with the Tulip driver. > > Ralf, is this patch appropriate? Can you please apply it or provide > some feedback. Runtime testing for that bug is fairly expensive as it adds a branch to every instance of every type of atomic operation. So we really want cpu_has_llsc to be a constant so the compiler can optimize that. So I suggest something like this in cpu-feature-overrides.h: [...] /* * R5000 has an interesting "restriction": ll(d)/sc(d) * instructions to XKPHYS region simply do uncached bus * requests. This breaks all the atomic bitops functions. * so, for 64bit IP32 kernel we just don't use ll/sc. * This does not affect luserland. */ #ifdef CONFIG_64BIT #define cpu_has_llsc 0 #else #define cpu_has_llsc 1 #endif [...] The probe would upset the IP27 cache coherency logic and crash them btw. Ralf
