On Fri, Nov 07, 2008 at 11:47:58AM -0500, Mathieu Desnoyers wrote: > But any get_cycles() user of cnt32_to_63() should be shot down. The > bright side is : there is no way get_cycles() can be used with this > new code. :) > > e.g. of incorrect users for arm (unless they are UP only, but that seems > like a weird design argument) : > > mach-sa1100/include/mach/SA-1100.h:#define OSCR __REG(0x90000010) > /* OS timer Counter Reg. */ > mach-sa1100/generic.c: unsigned long long v = cnt32_to_63(OSCR); > mach-pxa/include/mach/pxa-regs.h:#define OSCR __REG(0x40A00010) /* OS > Timer Counter Register */ > mach-pxa/time.c: unsigned long long v = cnt32_to_63(OSCR); It's strange for you to make that assertion when PXA was the exact platform that Nicolas created this code for - and that's a platform where preempt has been widely used. The two you mention are both ARMv5 or older architectures, and the first real SMP ARM architecture is ARMv6. So architecturally they are UP only. So, tell me why you say "unless they are UP only, but that seems like a weird design argument"? If the platforms can only ever be UP only, what's wrong with UP only code being used with them? (Not that I'm saying anything there about cnt32_to_63.) I'd like to see you modify the silicon of a PXA or SA11x0 SoC to add more than one processor to the chip - maybe you could use evostick to glue two dies together and a microscope to aid bonding wires between the two? (Of course, you'd need to design something to ensure cache coherence as well, and arbitrate the internal bus between the two dies.) ;) Personally, I think that's highly unlikely. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
