On 24 Mar 11 16:14, Colin Cross wrote: > 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. Yes, this is effectively my option #2 (reserve memory after the tags are parsed and before paging_init). This looks like a good approach. Thanks. Larry > -- > 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 -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- 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
