This option enables various optimizations for running under the KVM hypervisor. Overhead for the kernel when not running inside KVM should be minimal. In case of doubt, say Y
Support for running natively on the hardware, i.e. without a hypervisor. This option is not user-selectable but should be selected by all platforms that need it.
Support from booting from Open Firmware or yaboot using an Open Firmware client interface. This enables the kernel to communicate with open firmware to retrieve system information such as the device tree. In case of doubt, say Y
Select this opton if your platform supports SMP and your interrupt controller provides less than 4 interrupts to each cpu. This will enable the generic code to multiplex the 4 messages on to one ipi.
This option enables a MPIC driver workaround for some chips that have a bug that causes some interrupt source information to not read back properly. It is safe to use on other chips as well, but enabling it uses about 8KB of memory to keep copies of the register contents in software.
Bus device driver for GX bus based adapters.
This adds support for frequency switching on Apple PowerBooks, this currently includes some models of iBook & Titanium PowerBook.
This adds support for frequency switching on Apple iMac G5, and some of the more recent desktop G5 machines as well.
This adds the support for frequency switching on PA Semi PWRficient processors.
Some versions of the PPC601 (the first PowerPC chip) have bugs which mean that extra synchronization instructions are required near certain instructions, typically those that make major changes to the CPU state. These extra instructions reduce performance slightly. If you say N here, these extra instructions will not be included, resulting in a kernel which will run faster but may not run at all on some systems with the PPC601 chip. If in doubt, say Y here.
G3 and G4 processors have an on-chip temperature sensor called the 'Thermal Assist Unit (TAU)', which, in theory, can measure the on-die temperature within 2-4 degrees Celsius. This option shows the current on-die temperature in /proc/cpuinfo if the cpu supports it. Unfortunately, on some chip revisions, this sensor is very inaccurate and in many cases, does not work at all, so don't assume the cpu temp is actually what /proc/cpuinfo says it is.
The TAU supports an interrupt driven mode which causes an interrupt whenever the temperature goes out of range. This is the fastest way to get notified the temp has exceeded a range. With this option off, a timer is used to re-check the temperature periodically. However, on some cpus it appears that the TAU interrupt hardware is buggy and can cause a situation which would lead unexplained hard lockups. Unless you are extending the TAU driver, or enjoy kernel/hardware debugging, leave this option off.
The TAU hardware can compare the temperature to an upper and lower bound. The default behavior is to show both the upper and lower bound in /proc/cpuinfo. If the range is large, the temperature is either changing a lot, or the TAU hardware is broken (likely on some G4's). If the range is small (around 4 degrees), the temperature is relatively stable. If you say Y here, a single temperature value, halfway between the upper and lower bounds, will be reported in /proc/cpuinfo. If in doubt, say N here.
The QUICC Engine (QE) is a new generation of communications coprocessors on Freescale embedded CPUs (akin to CPM in older chips). Selecting this option means that you wish to build a kernel for a machine with a QE coprocessor.
Say Y here if you're going to use hardware that connects to the QE GPIOs.
The CPM2 (Communications Processor Module) is a coprocessor on embedded CPUs made by Freescale. Selecting this option means that you wish to build a kernel for a machine with a CPM2 coprocessor on it (826x, 827x, 8560).
It registers one block device per Axon's DDR2 memory bank found on a system. Block devices are called axonram?, their major and minor numbers are available in /proc/devices, /proc/partitions or in /sys/block/axonram?/dev.
Supports for the ULI1575 PCIe south bridge that exists on some Freescale reference boards. The boards all use the ULI in pretty much the same way.
Uses information from the OF or flattened device tree to instantiate platform devices for direct mapped RTC chips like the DS1742 or DS1743.
Say Y here if you're going to use hardware that connects to the MPC512x/831x/834x/837x/8572/8610 GPIOs.
Say Y here to support simple, memory-mapped GPIO controllers. These are usually BCSRs used to control board's switches, LEDs, chip-selects, Ethernet/USB PHY's power and various other small on-board peripherals.
Say Y here to enable soft power-off functionality on the Freescale boards with the MPC8349E-mITX-compatible MCU chips. This driver will also register MCU GPIOs with the generic GPIO API, so you'll able to use MCU pins as GPIOs.