On Tue, 2009-02-03 at 15:50 +0000, Martyn Welch wrote: > > The primary CPU is spinning in smp_generic_give_timebase() waiting for > "!tbsync->ack". The secondary CPU has made it into > smp_generic_take_timebase() and has apparently (according to some > printk's I put in there) set "tbsync->ack=1". After that I don't get > any printk's, I guess that the one I have put in the "! > tbsync->handshake" while loop is making it to the print buffer, but > with both processors spinning it's not getting to the serial console. > > At a guess, given that commit 64b3d0e8122b422e879b23d42f9e0e8efbbf9744 > seems to be the point that it stopped working correctly, that "tbsync" > is now somehow becoming cached? > Maybe we are missing the M bit in the mapping ?
Let's see... the kernel mapping is done via BATs on those guys (ie, e600 is a hash table based processor right ? some kind of 74xx). The code that sets them up is in arch/powerpc/mm/ppc_mmu_32.c In mmu_mapin_ram() we call setbat() multiple times. The last argument is the "flags" which is set to _PAGE_RAM. That should contain _PAGE_COHERENT when CONFIG_SMP is set unless I screwed up. IE. _PAGE_RAM is _PAGE_KERNEL | _PAGE_HWEXEC. _PAGE_KERNEL is _PAGE_BASE plus things, and _PAGE_BASE should contains _PAGE_COHERENT if CONFIG_SMP or CONFIG_PPC_STD_MMU are set and they should both be in your case. setbat() itself will clear _PAGE_COHERENT under some circumstances however. Either if the flags contain _PAGE_NO_CACHE, which should not be the case here, or if the CPU feature bit CPU_FTR_NEED_COHERENT is -not- set. I think that could be the cause of the problem. CPU_FTR_NEED_COHERENT is set as part of CPU_FTR_COMMON if CONFIG_SMP is set (among other things). So it -should- be set for you. since CPU_FTR_COMMON should be OR'ed with all CPU table entries. So I'm a bit at a loss here... unless something else went wrong. Please let me know what you find out. Cheers, Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
