On Tue, Feb 8, 2011 at 4:55 PM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Tue, Feb 08, 2011 at 05:47:18PM +0100, Arnd Bergmann wrote: >> On Tuesday 08 February 2011 17:25:16 Russell King - ARM Linux wrote: >> > On Tue, Feb 08, 2011 at 04:15:15PM +0100, Arnd Bergmann wrote: >> > > But that doesn't work if you build a combined v5/v6/v7 kernel, because >> > > v5 supports neither form, right? I think to do that, it needs the >> > > same kind of abstraction that we have for a number of other things >> > > like cache management in arch/arm/mm/. >> > >> > The options are kernels which support v3-v5 or v6-v7. There's too big >> > a change between v5 and v6 to combine those into one kernel. >> >> Ah, good to know. I never realized this with the common binary discussions. >> Building for the versatile/realview platform makes it possible to select >> any of ARM926 and the v6/v6k/v7 CPUs, as well as ARM7TDMI in the same >> kernel config, so I assumed that this was actually a valid configuration >> aside from bugs. >> >> Would an attempt to make a combined v5/v6 kernel result in unacceptably >> bad code, or is this just too much work for anyone to be bothered with >> and little practical value? > > If you build for anything less than v6, you lose all barriers, the icache > synchronization, and proper atomic operations. Just to name a few. > Can we represent the restriction in Kconfig somehow? For example: CPU_V6 depends on CPU_COMMON_V6PLUS CPU_V7 depends on CPU_COMMON_V6PLUS CPU_V5 depends on CPU_COMMON_V3_TO_V5 CPU_V4 depends on CPU_COMMON_V3_TO_V5 CPU_V3 depends on CPU_COMMON_V3_TO_V5 CPU_COMMON_V6PLUS depends on !CPU_COMMON_V3_TO_V5 CPU_COMMON_V3_TO_V5 depends on !CPU_COMMON_V6PLUS ...or something like that. ---Dave -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
