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linux/arch/xtensa/Kconfig

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# For a description of the syntax of this configuration file,
# see Documentation/kbuild/kconfig-language.txt.
mainmenu "Linux/Xtensa Kernel Configuration"
config FRAME_POINTER
bool
default n
config ZONE_DMA
bool
default y
config XTENSA
bool
default y
select HAVE_IDE
help
Xtensa processors are 32-bit RISC machines designed by Tensilica
primarily for embedded systems. These processors are both
configurable and extensible. The Linux port to the Xtensa
architecture supports all processor configurations and extensions,
with reasonable minimum requirements. The Xtensa Linux project has
a home page at <http://xtensa.sourceforge.net/>.
config RWSEM_XCHGADD_ALGORITHM
bool
default y
config GENERIC_FIND_NEXT_BIT
bool
default y
config GENERIC_HWEIGHT
bool
default y
config GENERIC_HARDIRQS
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config NO_IOPORT
def_bool y
avoid overflows in kernel/time.c When the conversion factor between jiffies and milli- or microseconds is not a single multiply or divide, as for the case of HZ == 300, we currently do a multiply followed by a divide. The intervening result, however, is subject to overflows, especially since the fraction is not simplified (for HZ == 300, we multiply by 300 and divide by 1000). This is exposed to the user when passing a large timeout to poll(), for example. This patch replaces the multiply-divide with a reciprocal multiplication on 32-bit platforms. When the input is an unsigned long, there is no portable way to do this on 64-bit platforms there is no portable way to do this since it requires a 128-bit intermediate result (which gcc does support on 64-bit platforms but may generate libgcc calls, e.g. on 64-bit s390), but since the output is a 32-bit integer in the cases affected, just simplify the multiply-divide (*3/10 instead of *300/1000). The reciprocal multiply used can have off-by-one errors in the upper half of the valid output range. This could be avoided at the expense of having to deal with a potential 65-bit intermediate result. Since the intent is to avoid overflow problems and most of the other time conversions are only semiexact, the off-by-one errors were considered an acceptable tradeoff. At Ralf Baechle's suggestion, this version uses a Perl script to compute the necessary constants. We already have dependencies on Perl for kernel compiles. This does, however, require the Perl module Math::BigInt, which is included in the standard Perl distribution starting with version 5.8.0. In order to support older versions of Perl, include a table of canned constants in the script itself, and structure the script so that Math::BigInt isn't required if pulling values from said table. Running the script requires that the HZ value is available from the Makefile. Thus, this patch also adds the Kconfig variable CONFIG_HZ to the architectures which didn't already have it (alpha, cris, frv, h8300, m32r, m68k, m68knommu, sparc, v850, and xtensa.) It does *not* touch the sh or sh64 architectures, since Paul Mundt has dealt with those separately in the sh tree. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Cc: Ralf Baechle <ralf@linux-mips.org>, Cc: Sam Ravnborg <sam@ravnborg.org>, Cc: Paul Mundt <lethal@linux-sh.org>, Cc: Richard Henderson <rth@twiddle.net>, Cc: Michael Starvik <starvik@axis.com>, Cc: David Howells <dhowells@redhat.com>, Cc: Yoshinori Sato <ysato@users.sourceforge.jp>, Cc: Hirokazu Takata <takata@linux-m32r.org>, Cc: Geert Uytterhoeven <geert@linux-m68k.org>, Cc: Roman Zippel <zippel@linux-m68k.org>, Cc: William L. Irwin <sparclinux@vger.kernel.org>, Cc: Chris Zankel <chris@zankel.net>, Cc: H. Peter Anvin <hpa@zytor.com>, Cc: Jan Engelhardt <jengelh@computergmbh.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 05:21:26 -07:00
config HZ
int
default 100
source "init/Kconfig"
menu "Processor type and features"
choice
prompt "Xtensa Processor Configuration"
default XTENSA_VARIANT_FSF
config XTENSA_VARIANT_FSF
bool "fsf"
endchoice
config MMU
bool
default y
config XTENSA_UNALIGNED_USER
bool "Unaligned memory access in use space"
---help---
The Xtensa architecture currently does not handle unaligned
memory accesses in hardware but through an exception handler.
Per default, unaligned memory accesses are disabled in user space.
Say Y here to enable unaligned memory access in user space.
config PREEMPT
bool "Preemptible Kernel"
---help---
This option reduces the latency of the kernel when reacting to
real-time or interactive events by allowing a low priority process to
be preempted even if it is in kernel mode executing a system call.
Unfortunately the kernel code has some race conditions if both
CONFIG_SMP and CONFIG_PREEMPT are enabled, so this option is
currently disabled if you are building an SMP kernel.
Say Y here if you are building a kernel for a desktop, embedded
or real-time system. Say N if you are unsure.
config MATH_EMULATION
bool "Math emulation"
help
Can we use information of configuration file?
config HIGHMEM
bool "High memory support"
endmenu
menu "Platform options"
choice
prompt "Xtensa System Type"
default XTENSA_PLATFORM_ISS
config XTENSA_PLATFORM_ISS
bool "ISS"
help
ISS is an acronym for Tensilica's Instruction Set Simulator.
config XTENSA_PLATFORM_XT2000
bool "XT2000"
help
XT2000 is the name of Tensilica's feature-rich emulation platform.
This hardware is capable of running a full Linux distribution.
endchoice
config XTENSA_CALIBRATE_CCOUNT
bool "Auto calibration of the CPU clock rate"
---help---
On some platforms (XT2000, for example), the CPU clock rate can
vary. The frequency can be determined, however, by measuring
against a well known, fixed frequency, such as an UART oscillator.
config XTENSA_CPU_CLOCK
int "CPU clock rate [MHz]"
depends on !XTENSA_CALIBRATE_CCOUNT
default "16"
config GENERIC_CALIBRATE_DELAY
bool "Auto calibration of the BogoMIPS value"
---help---
The BogoMIPS value can easily be derived from the CPU frequency.
config CMDLINE_BOOL
bool "Default bootloader kernel arguments"
config CMDLINE
string "Initial kernel command string"
depends on CMDLINE_BOOL
default "console=ttyS0,38400 root=/dev/ram"
help
On some architectures (EBSA110 and CATS), there is currently no way
for the boot loader to pass arguments to the kernel. For these
architectures, you should supply some command-line options at build
time by entering them here. As a minimum, you should specify the
memory size and the root device (e.g., mem=64M root=/dev/nfs).
config SERIAL_CONSOLE
bool
depends on XTENSA_PLATFORM_ISS
default y
config XTENSA_ISS_NETWORK
bool
depends on XTENSA_PLATFORM_ISS
default y
source "mm/Kconfig"
endmenu
menu "Bus options"
config PCI
bool "PCI support" if !XTENSA_PLATFORM_ISS
depends on !XTENSA_PLATFORM_ISS
default y
help
Find out whether you have a PCI motherboard. PCI is the name of a
bus system, i.e. the way the CPU talks to the other stuff inside
your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
VESA. If you have PCI, say Y, otherwise N.
source "drivers/pci/Kconfig"
config HOTPLUG
bool "Support for hot-pluggable devices"
---help---
Say Y here if you want to plug devices into your computer while
the system is running, and be able to use them quickly. In many
cases, the devices can likewise be unplugged at any time too.
One well known example of this is PCMCIA- or PC-cards, credit-card
size devices such as network cards, modems or hard drives which are
plugged into slots found on all modern laptop computers. Another
example, used on modern desktops as well as laptops, is USB.
Enable HOTPLUG and build a modular kernel. Get agent software
(from <http://linux-hotplug.sourceforge.net/>) and install it.
Then your kernel will automatically call out to a user mode "policy
agent" (/sbin/hotplug) to load modules and set up software needed
to use devices as you hotplug them.
source "drivers/pcmcia/Kconfig"
source "drivers/pci/hotplug/Kconfig"
endmenu
menu "Executable file formats"
# only elf supported
config KCORE_ELF
bool
depends on PROC_FS
default y
help
If you enabled support for /proc file system then the file
/proc/kcore will contain the kernel core image in ELF format. This
can be used in gdb:
$ cd /usr/src/linux ; gdb vmlinux /proc/kcore
This is especially useful if you have compiled the kernel with the
"-g" option to preserve debugging information. It is mainly used
for examining kernel data structures on the live kernel.
source "fs/Kconfig.binfmt"
endmenu
source "net/Kconfig"
source "drivers/Kconfig"
source "fs/Kconfig"
menu "Xtensa initrd options"
depends on BLK_DEV_INITRD
config EMBEDDED_RAMDISK
bool "Embed root filesystem ramdisk into the kernel"
config EMBEDDED_RAMDISK_IMAGE
string "Filename of gzipped ramdisk image"
depends on EMBEDDED_RAMDISK
default "ramdisk.gz"
help
This is the filename of the ramdisk image to be built into the
kernel. Relative pathnames are relative to arch/xtensa/boot/ramdisk/.
The ramdisk image is not part of the kernel distribution; you must
provide one yourself.
endmenu
source "arch/xtensa/Kconfig.debug"
source "security/Kconfig"
source "crypto/Kconfig"
source "lib/Kconfig"