On Thu, Mar 24, 2011 at 3:18 PM, Larry Bassel <lbassel@xxxxxxxxxxxxxx> wrote: > I want to (early in system initialization) exclude some > contiguous physical memory from one or more memory banks > so that it won't be mapped in the normal kernel 1-to-1 mapping > (so that it can be mapped uncached, strongly ordered, etc. > as needed -- I know that it is forbidden to have a cached > and an uncached mapping to the same memory) and so that it > won't be freed into the kernel memory allocator (so that > it won't fragment and can be allocated using genalloc). > > I have tried to find a clean way to do this, but none of > the approaches I've considered seem very good: > > 1. Add a hook to the memory tag parsing routine to (possibly) > change each tag before arm_add_memory() is called, > or alter arm_add_memory() itself. > 2. Add a hook at the beginning of paging_init() to inspect > and alter the meminfo memory bank starts and sizes as needed. > 3. Wait until after the memory is added to the normal > kernel memory pool and somehow get it back out > (I can't use alloc_bootmem() or related functionality of course > since then the memory will be part of the cached kernel 1-to-1 1M > page mapping, precluding use of ioremap() on it). > > A further drawback for #1 is that I'd really like to > see all of the available memory banks before deciding which > memory to steal (we often have multiple memory banks on > our platforms). > > Perhaps there is a solution for this problem that already exists > that I'm unaware of (or at least community consensus about how > one should add this functionality). > > I believe Russell King has stated that he intends > to carve out memory that can be used for dma_alloc_coherent(), > that won't be mapped otherwise by the kernel. > > I'd like to know how he is planning to do this, as I could hopefully > do something similar. > > Thanks. > > Larry Bassel You want memblock_remove, called from the new .reserve machine entry function. See arch/arm/plat-omap/devices.c for an example. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
