bdc807871d
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>
227 lines
4 KiB
Text
227 lines
4 KiB
Text
#
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# For a description of the syntax of this configuration file,
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# see the Configure script.
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#
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mainmenu "Linux/CRIS Kernel Configuration"
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config MMU
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bool
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default y
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config ZONE_DMA
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bool
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default y
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config NO_DMA
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bool
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default y
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config RWSEM_GENERIC_SPINLOCK
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bool
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default y
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config RWSEM_XCHGADD_ALGORITHM
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bool
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config ARCH_HAS_ILOG2_U32
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bool
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default n
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config ARCH_HAS_ILOG2_U64
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bool
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default n
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config GENERIC_FIND_NEXT_BIT
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bool
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default y
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config GENERIC_HWEIGHT
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bool
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default y
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config GENERIC_CALIBRATE_DELAY
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bool
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default y
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config IRQ_PER_CPU
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bool
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default y
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config NO_IOPORT
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def_bool y
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config CRIS
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bool
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default y
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config HZ
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int
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default 100
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source "init/Kconfig"
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menu "General setup"
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source "fs/Kconfig.binfmt"
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config GENERIC_HARDIRQS
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bool
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default y
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config ETRAX_CMDLINE
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string "Kernel command line"
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default "root=/dev/mtdblock3"
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help
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Pass additional commands to the kernel.
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config ETRAX_WATCHDOG
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bool "Enable ETRAX watchdog"
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help
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Enable the built-in watchdog timer support on ETRAX based embedded
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network computers.
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config ETRAX_WATCHDOG_NICE_DOGGY
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bool "Disable watchdog during Oops printouts"
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depends on ETRAX_WATCHDOG
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help
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By enabling this you make sure that the watchdog does not bite while
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printing oopses. Recommended for development systems but not for
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production releases.
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config ETRAX_FAST_TIMER
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bool "Enable ETRAX fast timer API"
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help
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This options enables the API to a fast timer implementation using
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timer1 to get sub jiffie resolution timers (primarily one-shot
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timers).
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This is needed if CONFIG_ETRAX_SERIAL_FAST_TIMER is enabled.
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config PREEMPT
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bool "Preemptible Kernel"
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help
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This option reduces the latency of the kernel when reacting to
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real-time or interactive events by allowing a low priority process to
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be preempted even if it is in kernel mode executing a system call.
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This allows applications to run more reliably even when the system is
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under load.
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Say Y here if you are building a kernel for a desktop, embedded
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or real-time system. Say N if you are unsure.
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source mm/Kconfig
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endmenu
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menu "Hardware setup"
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choice
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prompt "Processor type"
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default ETRAX100LX
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config ETRAX100LX
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bool "ETRAX-100LX-v1"
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help
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Support version 1 of the ETRAX 100LX.
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config ETRAX100LX_V2
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bool "ETRAX-100LX-v2"
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help
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Support version 2 of the ETRAX 100LX.
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config SVINTO_SIM
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bool "ETRAX-100LX-for-xsim-simulator"
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help
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Support the xsim ETRAX Simulator.
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endchoice
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config ETRAX_ARCH_V10
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bool
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default y if ETRAX100LX || ETRAX100LX_V2
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default n if !(ETRAX100LX || ETRAX100LX_V2)
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config ETRAX_DRAM_SIZE
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int "DRAM size (dec, in MB)"
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default "8"
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help
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Size of DRAM (decimal in MB) typically 2, 8 or 16.
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config ETRAX_FLASH_BUSWIDTH
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int "Buswidth of flash in bytes"
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default "2"
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help
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Width in bytes of the Flash bus (1, 2 or 4). Is usually 2.
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source arch/cris/arch-v10/Kconfig
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source arch/cris/arch-v32/Kconfig
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endmenu
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source "net/Kconfig"
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# bring in ETRAX built-in drivers
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menu "Drivers for built-in interfaces"
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source arch/cris/arch-v10/drivers/Kconfig
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source arch/cris/arch-v32/drivers/Kconfig
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endmenu
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source "drivers/base/Kconfig"
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# standard linux drivers
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source "drivers/mtd/Kconfig"
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source "drivers/parport/Kconfig"
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source "drivers/pnp/Kconfig"
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source "drivers/block/Kconfig"
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source "drivers/md/Kconfig"
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source "drivers/ide/Kconfig"
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source "drivers/scsi/Kconfig"
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source "drivers/ieee1394/Kconfig"
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source "drivers/message/i2o/Kconfig"
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source "drivers/net/Kconfig"
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source "drivers/isdn/Kconfig"
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source "drivers/telephony/Kconfig"
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source "drivers/i2c/Kconfig"
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source "drivers/rtc/Kconfig"
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#
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# input before char - char/joystick depends on it. As does USB.
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#
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source "drivers/input/Kconfig"
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source "drivers/char/Kconfig"
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#source drivers/misc/Config.in
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source "drivers/media/Kconfig"
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source "fs/Kconfig"
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source "sound/Kconfig"
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source "drivers/pcmcia/Kconfig"
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source "drivers/pci/Kconfig"
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source "drivers/usb/Kconfig"
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source "arch/cris/Kconfig.debug"
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source "security/Kconfig"
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source "crypto/Kconfig"
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source "lib/Kconfig"
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