On Fri, Jun 27, 2014 at 1:10 AM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Thu, Jun 26, 2014 at 11:53:20PM +0900, Alexandre Courbot wrote: >> We don't plan to rely on CMA for too long. IOMMU support is on the way >> and should make our life easier, although no matter the source of >> memory, we will still have the issue of the lowmem mappings. > > When it comes to DMA memory, talking about lowmem vs highmem is utterly > meaningless. > > The lowmem/highmem split is entirely a software concept and is completely > adjustable. An extreme example is that you can boot any platform with > more than 32MB of memory with 32MB of lowmem and the remainder as > highmem. True, but isn't it also the case that all lowmem is already mapped in the kernel address space, and that re-mapping this memory with different cache settings (e.g. by creating a WC mapping for user-space to write into) is undefined on ARM and must be avoided? That is the issue I was referring to. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
