> I'm currently trying to port a (currently for unreleased hardware and > under nda) driver from x86 to arm and in doing so I've run into a > problem with allocating memory using pci_alloc_consistent. Looking into > it I can't allocate more than 1MB whereas I need to allocate at least > 2MB of contiguous memory. I guess pci_alloc_consistent calls dma_alloc_coherent, so why does it fail to allocate 2MB of memory? What is the error do you see? Looking further into it, the conventional > method to get around this at the moment seems to be to statically link > the driver into the kernel and use alloc_bootmem or alloc_bootmem_low > (mentioned in ldd3 and all over google). > > The problem I've run into however is that I get a warning at boot which is: > > WARNING: at mm/bootmem.c:672 alloc_arch_preferred_bootmem+0x34/0x64() You need to call alloc_bootmem at an early stage before slab is initialized. > > Looking at that code in bootmem.c this is a warning which I think is > there to tell me that SLAB is available and warn against trying to > allocate at boot. However it reportedly allocates the memory but when > the driver tries to use this memory later, then the system hangs. Is the driver using the memory for DMA? Are you using the memory returned by alloc_bootmem directly? Remember DMA works on physical addresses not virtual. You might have to use dma_map_single/dma_unmap_single. Also does the h/w has any limitations of the physical memory range it can access? Like only first 64MB of RAM? regards -syed _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
