On Tue, Apr 27, 2010 at 02:14:32PM +0200, Manuel Lauss wrote: > I'd like to use bootmem to reserve large chunks of RAM (at a particular physical > address; for Au1200 MAE, CIM and framebuffer, and later Au1300 OpenGL block) > but it seems that it can't be done: Doing __alloc_bootmem() in > plat_mem_setup() is > too early, while an arch_initcall() is too late because by then the > slab allocator is > already up and handing out random addresses and/or refusing allocations larger > than a few MBytes. The maximum is actually configurable. CONFIG_FORCE_MAX_ZONEORDER defaults to 11 which means with 4kB pages you get 8MB maximum allocation - more for larger pages. CONFIG_FORCE_MAX_ZONEORDER is a tradeoff though. A smaller value will give slightly better performance and safe a bit of memory but I can't really quantify these numbers - I assume it's a small difference. It may actually be preferable to never tell the bootmem allocator about the memory you need for these devices that is bypass the mm code entirely. > Is there another callback I could use which would allow me to use bootmem (short > of abusing plat_smp_setup)? > > Would a separate callback like this be an acceptable solution? Certainly better than using plat_smp_setup which would require enabling SMP support for no good reason at all. I know we will eventually have to add another platform hooks to run after bootmem_init. The name of plat_mem_setup() already shows what this hook originally was meant for but it ended up as the everything-and-the-kitchen- sink hook for platform-specific early initialization. I just dislike conditional hooks. Let's add a call to a new hook function and fix whatever breaks or think about what other hooks needs there should be. Ralf
