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linux/arch/v850/Kconfig
H. Peter Anvin bdc807871d 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 09:22:39 -08:00

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#############################################################################
#
# For a description of the syntax of this configuration file,
# see Documentation/kbuild/kconfig-language.txt.
#
#############################################################################
mainmenu "uClinux/v850 (w/o MMU) Kernel Configuration"
config MMU
bool
default n
config ZONE_DMA
bool
default y
config RWSEM_GENERIC_SPINLOCK
bool
default y
config RWSEM_XCHGADD_ALGORITHM
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
config GENERIC_HWEIGHT
bool
default y
config GENERIC_CALIBRATE_DELAY
bool
default y
config GENERIC_HARDIRQS
bool
default y
config GENERIC_IRQ_PROBE
bool
default y
config GENERIC_TIME
bool
default y
config TIME_LOW_RES
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config ARCH_SUPPORTS_AOUT
def_bool y
# Turn off some random 386 crap that can affect device config
config ISA
bool
default n
config ISAPNP
bool
default n
config EISA
bool
default n
config MCA
bool
default n
#############################################################################
#### v850-specific config
# Define the architecture
config V850
bool
default y
menu "Processor type and features"
choice
prompt "Platform"
default GDB
config V850E_SIM
bool "GDB"
config RTE_CB_MA1
bool "RTE-V850E/MA1-CB"
config RTE_CB_NB85E
bool "RTE-V850E/NB85E-CB"
config RTE_CB_ME2
bool "RTE-V850E/ME2-CB"
config V850E_AS85EP1
bool "AS85EP1"
config V850E2_SIM85E2C
bool "sim85e2c"
config V850E2_SIM85E2S
bool "sim85e2s"
config V850E2_FPGA85E2C
bool "NA85E2C-FPGA"
config V850E2_ANNA
bool "Anna"
endchoice
#### V850E processor-specific config
# All CPUs currently supported use the v850e architecture
config V850E
bool
default y
# The RTE-V850E/MA1-CB is the only type of V850E/MA1 platform we
# currently support
config V850E_MA1
bool
depends on RTE_CB_MA1
default y
# Similarly for the RTE-V850E/NB85E-CB - V850E/TEG
config V850E_TEG
bool
depends on RTE_CB_NB85E
default y
# ... and the RTE-V850E/ME2-CB - V850E/ME2
config V850E_ME2
bool
depends on RTE_CB_ME2
default y
#### sim85e2-specific config
config V850E2_SIM85E2
bool
depends on V850E2_SIM85E2C || V850E2_SIM85E2S
default y
#### V850E2 processor-specific config
# V850E2 processors
config V850E2
bool
depends on V850E2_SIM85E2 || V850E2_FPGA85E2C || V850E2_ANNA
default y
#### RTE-CB platform-specific config
# Boards in the RTE-x-CB series
config RTE_CB
bool
depends on RTE_CB_MA1 || RTE_CB_NB85E || RTE_CB_ME2
default y
config RTE_CB_MULTI
bool
# RTE_CB_NB85E can either have multi ROM support or not, but
# other platforms (currently only RTE_CB_MA1) require it.
prompt "Multi monitor ROM support" if RTE_CB_NB85E
depends on RTE_CB_MA1 || RTE_CB_NB85E
default y
config RTE_CB_MULTI_DBTRAP
bool "Pass illegal insn trap / dbtrap to kernel"
depends on RTE_CB_MULTI
default n
config RTE_CB_MA1_KSRAM
bool "Kernel in SRAM (limits size of kernel)"
depends on RTE_CB_MA1 && RTE_CB_MULTI
default n
config RTE_MB_A_PCI
bool "Mother-A PCI support"
depends on RTE_CB
default y
# The GBUS is used to talk to the RTE-MOTHER-A board
config RTE_GBUS_INT
bool
depends on RTE_MB_A_PCI
default y
# The only PCI bus we support is on the RTE-MOTHER-A board
config PCI
bool
default RTE_MB_A_PCI
#### Some feature-specific configs
# Everything except for the GDB simulator uses the same interrupt controller
config V850E_INTC
bool
default !V850E_SIM
# Everything except for the various simulators uses the "Timer D" unit
config V850E_TIMER_D
bool
default !V850E_SIM && !V850E2_SIM85E2
# Cache control used on some v850e1 processors
config V850E_CACHE
bool
default V850E_TEG || V850E_ME2
# Cache control used on v850e2 processors; I think this should
# actually apply to more, but currently only the SIM85E2S uses it
config V850E2_CACHE
bool
default V850E2_SIM85E2S
config NO_CACHE
bool
default !V850E_CACHE && !V850E2_CACHE
# HZ depends on the platform
config HZ
int
default 24 if V850E_SIM || V850E2_SIM85E2
default 122 if V850E2_FPGA85E2C
default 100
#### Misc config
config ROM_KERNEL
bool "Kernel in ROM"
depends on V850E2_ANNA || V850E_AS85EP1 || RTE_CB_ME2
# Some platforms pre-zero memory, in which case the kernel doesn't need to
config ZERO_BSS
bool
depends on !V850E2_SIM85E2C
default y
# The crappy-ass zone allocator requires that the start of allocatable
# memory be aligned to the largest possible allocation.
config FORCE_MAX_ZONEORDER
int
default 8 if V850E2_SIM85E2C || V850E2_FPGA85E2C
config V850E_HIGHRES_TIMER
bool "High resolution timer support"
depends on V850E_TIMER_D
config TIME_BOOTUP
bool "Time bootup"
depends on V850E_HIGHRES_TIMER
config RESET_GUARD
bool "Reset Guard"
source "mm/Kconfig"
endmenu
#############################################################################
source init/Kconfig
#############################################################################
menu "Bus options (PCI, PCMCIA, EISA, MCA, ISA)"
# config PCI
# bool "PCI support"
# help
# Support for PCI bus.
source "drivers/pci/Kconfig"
source "drivers/pcmcia/Kconfig"
source "drivers/pci/hotplug/Kconfig"
endmenu
menu "Executable file formats"
source "fs/Kconfig.binfmt"
endmenu
source "net/Kconfig"
#############################################################################
source "drivers/base/Kconfig"
source drivers/mtd/Kconfig
source drivers/parport/Kconfig
#source drivers/pnp/Kconfig
source drivers/block/Kconfig
#############################################################################
menu "Disk device support"
source "drivers/ide/Kconfig"
source "drivers/scsi/Kconfig"
endmenu
#############################################################################
source "drivers/md/Kconfig"
source "drivers/message/fusion/Kconfig"
source "drivers/ieee1394/Kconfig"
source "drivers/message/i2o/Kconfig"
source "drivers/net/Kconfig"
source "drivers/isdn/Kconfig"
#source "drivers/telephony/Kconfig"
#
# input before char - char/joystick depends on it. As does USB.
#
source "drivers/input/Kconfig"
source "drivers/char/Kconfig"
#source drivers/misc/Config.in
source "drivers/media/Kconfig"
source "fs/Kconfig"
source "drivers/video/Kconfig"
source "sound/Kconfig"
source "drivers/usb/Kconfig"
source "arch/v850/Kconfig.debug"
source "security/Kconfig"
source "crypto/Kconfig"
source "lib/Kconfig"
#############################################################################
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