Generic GPIO API support
Used to allow a board to specify it wants a uImage built by default default n
Some PowerPC chips designed for embedded applications do not have a floating-point unit and therefore do not implement the floating-point instructions in the PowerPC instruction set. If you say Y here, the kernel will include code to emulate a floating-point unit, which will allow programs that use floating-point instructions to run.
Older arch/ppc kernels still emulated a few floating point instructions such as load and store, even when full math emulation is disabled. Say "Y" here if you want to preserve this behavior. It is recommended that you build a soft-float userspace instead.
Cause IO segments sent to a device for DMA to be merged virtually by the IOMMU when they happen to have been allocated contiguously. This doesn't add pressure to the IOMMU allocator. However, some drivers don't support getting large merged segments coming back from *_map_sg(). Most drivers don't have this problem; it is safe to say Y here.
Support for IO bounce buffering for systems without an IOMMU. This allows us to DMA to the full physical address space on platforms where the size of a physical address is larger than the bus address. Not all platforms support this.
Say Y here to be able to disable and re-enable individual CPUs at runtime on SMP machines. Say N if you are unsure.
kexec is a system call that implements the ability to shutdown your current kernel, and to start another kernel. It is like a reboot but it is independent of the system firmware. And like a reboot you can start any kernel with it, not just Linux. The name comes from the similarity to the exec system call. It is an ongoing process to be certain the hardware in a machine is properly shutdown, so do not be surprised if this code does not initially work for you. It may help to enable device hotplugging support. As of this writing the exact hardware interface is strongly in flux, so no good recommendation can be made.
Build a kernel suitable for use as a kdump capture kernel. The same kernel binary can be used as production kernel and dump capture kernel.
Hypervisor-assisted dump is meant to be a kdump replacement offering robustness and speed not possible without system hypervisor assistance. If unsure, say "N"
This option gives the kernel permission to distribute IRQs across multiple CPUs. Saying N here will route all IRQs to the first CPU. Generally saying Y is safe, although some problems have been reported with SMP Power Macintoshes with this option enabled.
Turning this option off allows you to select 256KB PAGE_SIZE on 44x. Note, that kernel will be able to run only those applications, which had been compiled using binutils later than 2.17.50.0.3 with '-zmax-page-size' set to 256K (the default is 64K). Or, if using the older binutils, you can patch them with a trivial patch, which changes the ELF_MAXPAGESIZE definition from 0x10000 to 0x40000.
Select the kernel logical page size. Increasing the page size will reduce software overhead at each page boundary, allow hardware prefetch mechanisms to be more effective, and allow larger dma transfers increasing IO efficiency and reducing overhead. However the utilization of memory will increase. For example, each cached file will using a multiple of the page size to hold its contents and the difference between the end of file and the end of page is wasted. Some dedicated systems, such as software raid serving with accelerated calculations, have shown significant increases. If you configure a 64 bit kernel for 64k pages but the processor does not support them, then the kernel will simulate them with 4k pages, loading them on demand, but with the reduced software overhead and larger internal fragmentation. For the 32 bit kernel, a large page option will not be offered unless it is supported by the configured processor. If unsure, choose 4K_PAGES.
Make the page size 256k. As the ELF standard only requires alignment to support page sizes up to 64k, you will need to compile all of your user space applications with a non-standard binutils settings (see the STDBINUTILS description for details). Say N unless you know what you are doing.
The kernel memory allocator divides physically contiguous memory blocks into "zones", where each zone is a power of two number of pages. This option selects the largest power of two that the kernel keeps in the memory allocator. If you need to allocate very large blocks of physically contiguous memory, then you may need to increase this value. This config option is actually maximum order plus one. For example, a value of 11 means that the largest free memory block is 2^10 pages. The page size is not necessarily 4KB. For example, on 64-bit systems, 64KB pages can be enabled via CONFIG_PPC_64K_PAGES. Keep this in mind when choosing a value for this option.
This option adds support for a system call to allow user programs to set access permissions (read/write, readonly, or no access) on the 4k subpages of each 64k page.
SMT scheduler support improves the CPU scheduler's decision making when dealing with POWER5 cpus at a cost of slightly increased overhead in some places. If unsure say N here.
This option adds a device-tree directory under /proc which contains an image of the device tree that the kernel copies from Open Firmware or other boot firmware. If unsure, say Y here.
On some platforms, there is currently no way for the boot loader to pass arguments to the kernel. For these platforms, you can supply some command-line options at build time by entering them here. In most cases you will need to specify the root device here.
List additional targets to be built by the bootwrapper here (separated by spaces). This is useful for targets that depend of device tree files in the .dts directory. Targets in this list will be build as part of the default build target, or when the user does a 'make zImage' or a 'make zImage.initrd'. If unsure, leave blank
This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their execution. By using pipes or other transports made available to the process as file descriptors supporting the read/write syscalls, it's possible to isolate those applications in their own address space using seccomp. Once seccomp is enabled via /proc/<pid>/seccomp, it cannot be disabled and the task is only allowed to execute a few safe syscalls defined by each seccomp mode. If unsure, say Y. Only embedded should say N here.
Find out whether you have ISA slots on your motherboard. ISA is the name of a bus system, i.e. the way the CPU talks to the other stuff inside your box. If you have an Apple machine, say N here; if you have an IBM RS/6000 or pSeries machine or a PReP machine, say Y. If you have an embedded board, consult your board documentation.
Freescale Localbus support
Freescale General-purpose Timers support
Find out whether your system includes a PCI bus. PCI is the name of a bus system, i.e. the way the CPU talks to the other stuff inside your box. If you say Y here, the kernel will include drivers and infrastructure code to support PCI bus devices.
Say Y here if you have a system based on a Motorola 8xx-series embedded processor with a QSPAN PCI interface, otherwise say N.
If you say Y here, the kernel will include drivers and infrastructure code to support RapidIO interconnect devices.
This option will enable prompting for a variety of advanced kernel configuration options. These options can cause the kernel to not work if they are set incorrectly, but can be used to optimize certain aspects of kernel memory management. Unless you know what you are doing, say N here.
This option allows you to set the maximum amount of memory which will be used as "low memory", that is, memory which the kernel can access directly, without having to set up a kernel virtual mapping. This can be useful in optimizing the layout of kernel virtual memory. Say N here unless you know what you are doing.
This option allows you to set the maximum number of CAM slots that will be used to map low memory. There are a limited number of slots available and even more limited number that will fit in the L1 MMU. However, using more entries will allow mapping more low memory. This can be useful in optimizing the layout of kernel virtual memory. Say N here unless you know what you are doing.
This builds a kernel image that is capable of running at the location the kernel is loaded at (some alignment restrictions may exist). One use is for the kexec on panic case where the recovery kernel must live at a different physical address than the primary kernel. Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address it has been loaded at and the compile time physical addresses CONFIG_PHYSICAL_START is ignored. However CONFIG_PHYSICAL_START setting can still be useful to bootwrappers that need to know the load location of the kernel (eg. u-boot/mkimage).
This option allows you to set the kernel virtual address at which the kernel will map low memory. This can be useful in optimizing the virtual memory layout of the system. Say N here unless you know what you are doing.
This option allows you to set the kernel virtual address at which the kernel will be loaded. Normally this should match PAGE_OFFSET however there are times (like kdump) that one might not want them to be the same. Say N here unless you know what you are doing.
This gives the physical address where the kernel is loaded. Say N here unless you know what you are doing.
This value puts the alignment restrictions on physical address where kernel is loaded and run from. Kernel is compiled for an address which meets above alignment restriction.
This option allows you to set the amount of virtual address space allocated to user tasks. This can be useful in optimizing the virtual memory layout of the system. Say N here unless you know what you are doing.
This option allows you to set the size of the consistent memory pool. This pool of virtual memory is used to make consistent memory allocations.
This builds a kernel image that is capable of running anywhere in the RMA (real memory area) at any 16k-aligned base address. The kernel is linked as a position-independent executable (PIE) and contains dynamic relocations which are processed early in the bootup process. One use is for the kexec on panic case where the recovery kernel must live at a different physical address than the primary kernel.