mirror of
https://github.com/torvalds/linux
synced 2024-11-05 18:23:50 +00:00
8e3e076c5a
The generic semaphore rewrite had a huge performance regression on AIM7
(and potentially other BKL-heavy benchmarks) because the generic
semaphores had been rewritten to be simple to understand and fair. The
latter, in particular, turns a semaphore-based BKL implementation into a
mess of scheduling.
The attempt to fix the performance regression failed miserably (see the
previous commit 00b41ec261 'Revert
"semaphore: fix"'), and so for now the simple and sane approach is to
instead just go back to the old spinlock-based BKL implementation that
never had any issues like this.
This patch also has the advantage of being reported to fix the
regression completely according to Yanmin Zhang, unlike the semaphore
hack which still left a couple percentage point regression.
As a spinlock, the BKL obviously has the potential to be a latency
issue, but it's not really any different from any other spinlock in that
respect. We do want to get rid of the BKL asap, but that has been the
plan for several years.
These days, the biggest users are in the tty layer (open/release in
particular) and Alan holds out some hope:
"tty release is probably a few months away from getting cured - I'm
afraid it will almost certainly be the very last user of the BKL in
tty to get fixed as it depends on everything else being sanely locked."
so while we're not there yet, we do have a plan of action.
Tested-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Alexander Viro <viro@ftp.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
374 lines
7.9 KiB
Text
374 lines
7.9 KiB
Text
#
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# For a description of the syntax of this configuration file,
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# see Documentation/kbuild/kconfig-language.txt.
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#
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mainmenu "Linux Kernel Configuration"
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config MN10300
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def_bool y
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config AM33
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def_bool y
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config MMU
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def_bool y
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config HIGHMEM
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def_bool n
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config NUMA
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def_bool n
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config UID16
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def_bool y
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config RWSEM_GENERIC_SPINLOCK
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def_bool y
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config RWSEM_XCHGADD_ALGORITHM
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bool
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config GENERIC_HARDIRQS_NO__DO_IRQ
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def_bool y
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config GENERIC_CALIBRATE_DELAY
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def_bool y
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config GENERIC_FIND_NEXT_BIT
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def_bool y
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config GENERIC_HWEIGHT
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def_bool y
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config GENERIC_TIME
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def_bool y
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config GENERIC_BUG
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def_bool y
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config QUICKLIST
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def_bool y
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config ARCH_HAS_ILOG2_U32
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def_bool y
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config ARCH_SUPPORTS_AOUT
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def_bool n
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# Use the generic interrupt handling code in kernel/irq/
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config GENERIC_HARDIRQS
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def_bool y
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config HOTPLUG_CPU
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def_bool n
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config HZ
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int
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default 1000
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mainmenu "Matsushita MN10300/AM33 Kernel Configuration"
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source "init/Kconfig"
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menu "Matsushita MN10300 system setup"
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choice
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prompt "Unit type"
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default MN10300_UNIT_ASB2303
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help
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This option specifies board for which the kernel will be
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compiled. It affects the external peripherals catered for.
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config MN10300_UNIT_ASB2303
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bool "ASB2303"
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config MN10300_UNIT_ASB2305
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bool "ASB2305"
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endchoice
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choice
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prompt "Processor support"
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default MN10300_PROC_MN103E010
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help
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This option specifies the processor for which the kernel will be
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compiled. It affects the on-chip peripherals catered for.
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config MN10300_PROC_MN103E010
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bool "MN103E010"
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depends on MN10300_UNIT_ASB2303 || MN10300_UNIT_ASB2305
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select MN10300_PROC_HAS_TTYSM0
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select MN10300_PROC_HAS_TTYSM1
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select MN10300_PROC_HAS_TTYSM2
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endchoice
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choice
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prompt "Processor core support"
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default MN10300_CPU_AM33V2
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help
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This option specifies the processor core for which the kernel will be
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compiled. It affects the instruction set used.
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config MN10300_CPU_AM33V2
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bool "AM33v2"
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endchoice
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config FPU
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bool "FPU present"
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default y
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depends on MN10300_PROC_MN103E010
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choice
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prompt "CPU Caching mode"
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default MN10300_CACHE_WBACK
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help
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This option determines the caching mode for the kernel.
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Write-Back caching mode involves the all reads and writes causing
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the affected cacheline to be read into the cache first before being
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operated upon. Memory is not then updated by a write until the cache
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is filled and a cacheline needs to be displaced from the cache to
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make room. Only at that point is it written back.
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Write-Through caching only fetches cachelines from memory on a
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read. Writes always get written directly to memory. If the affected
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cacheline is also in cache, it will be updated too.
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The final option is to turn of caching entirely.
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config MN10300_CACHE_WBACK
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bool "Write-Back"
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config MN10300_CACHE_WTHRU
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bool "Write-Through"
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config MN10300_CACHE_DISABLED
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bool "Disabled"
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endchoice
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menu "Memory layout options"
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config KERNEL_RAM_BASE_ADDRESS
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hex "Base address of kernel RAM"
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default "0x90000000"
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config INTERRUPT_VECTOR_BASE
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hex "Base address of vector table"
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default "0x90000000"
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help
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The base address of the vector table will be programmed into
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the TBR register. It must be on 16MiB address boundary.
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config KERNEL_TEXT_ADDRESS
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hex "Base address of kernel"
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default "0x90001000"
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config KERNEL_ZIMAGE_BASE_ADDRESS
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hex "Base address of compressed vmlinux image"
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default "0x90700000"
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endmenu
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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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config MN10300_CURRENT_IN_E2
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bool "Hold current task address in E2 register"
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default y
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help
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This option removes the E2/R2 register from the set available to gcc
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for normal use and instead uses it to store the address of the
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current process's task_struct whilst in the kernel.
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This means the kernel doesn't need to calculate the address each time
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"current" is used (take SP, AND with mask and dereference pointer
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just to get the address), and instead can just use E2+offset
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addressing each time.
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This has no effect on userspace.
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config MN10300_USING_JTAG
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bool "Using JTAG to debug kernel"
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default y
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help
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This options indicates that JTAG will be used to debug the kernel. It
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suppresses the use of certain hardware debugging features, such as
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single-stepping, which are taken over completely by the JTAG unit.
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config MN10300_RTC
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bool "Using MN10300 RTC"
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depends on MN10300_PROC_MN103E010
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default n
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help
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This option enables support for the RTC, thus enabling time to be
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tracked, even when system is powered down. This is available on-chip
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on the MN103E010.
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config MN10300_WD_TIMER
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bool "Using MN10300 watchdog timer"
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default y
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help
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This options indicates that the watchdog timer will be used.
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config PCI
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bool "Use PCI"
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depends on MN10300_UNIT_ASB2305
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default y
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help
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Some systems (such as the ASB2305) have PCI onboard. If you have one
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of these boards and you wish to use the PCI facilities, say Y here.
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The PCI-HOWTO, available from
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<http://www.tldp.org/docs.html#howto>, contains valuable
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information about which PCI hardware does work under Linux and which
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doesn't.
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source "drivers/pci/Kconfig"
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source "drivers/pcmcia/Kconfig"
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menu "MN10300 internal serial options"
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config MN10300_PROC_HAS_TTYSM0
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bool
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default n
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config MN10300_PROC_HAS_TTYSM1
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bool
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default n
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config MN10300_PROC_HAS_TTYSM2
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bool
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default n
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config MN10300_TTYSM
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bool "Support for ttySM serial ports"
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depends on MN10300
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default y
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select SERIAL_CORE
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help
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This option enables support for the on-chip serial ports that the
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MN10300 has available.
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config MN10300_TTYSM_CONSOLE
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bool "Support for console on ttySM serial ports"
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depends on MN10300_TTYSM
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select SERIAL_CORE_CONSOLE
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help
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This option enables support for a console on the on-chip serial ports
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that the MN10300 has available.
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#
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# /dev/ttySM0
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#
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config MN10300_TTYSM0
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bool "Enable SIF0 (/dev/ttySM0)"
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depends on MN10300_TTYSM && MN10300_PROC_HAS_TTYSM0
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help
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Enable access to SIF0 through /dev/ttySM0 or gdb-stub
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choice
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prompt "Select the timer to supply the clock for SIF0"
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default MN10300_TTYSM0_TIMER8
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depends on MN10300_TTYSM0
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config MN10300_TTYSM0_TIMER8
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bool "Use timer 8 (16-bit)"
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config MN10300_TTYSM0_TIMER2
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bool "Use timer 2 (8-bit)"
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endchoice
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#
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# /dev/ttySM1
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#
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config MN10300_TTYSM1
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bool "Enable SIF1 (/dev/ttySM1)"
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depends on MN10300_TTYSM && MN10300_PROC_HAS_TTYSM1
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help
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Enable access to SIF1 through /dev/ttySM1 or gdb-stub
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choice
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prompt "Select the timer to supply the clock for SIF1"
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default MN10300_TTYSM0_TIMER9
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depends on MN10300_TTYSM1
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config MN10300_TTYSM1_TIMER9
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bool "Use timer 9 (16-bit)"
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config MN10300_TTYSM1_TIMER3
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bool "Use timer 3 (8-bit)"
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endchoice
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#
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# /dev/ttySM2
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#
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config MN10300_TTYSM2
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bool "Enable SIF2 (/dev/ttySM2)"
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depends on MN10300_TTYSM && MN10300_PROC_HAS_TTYSM2
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help
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Enable access to SIF2 through /dev/ttySM2 or gdb-stub
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choice
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prompt "Select the timer to supply the clock for SIF2"
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default MN10300_TTYSM0_TIMER10
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depends on MN10300_TTYSM2
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config MN10300_TTYSM2_TIMER10
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bool "Use timer 10 (16-bit)"
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endchoice
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config MN10300_TTYSM2_CTS
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bool "Enable the use of the CTS line /dev/ttySM2"
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depends on MN10300_TTYSM2
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endmenu
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source "mm/Kconfig"
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menu "Power management options"
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source kernel/power/Kconfig
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endmenu
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endmenu
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menu "Executable formats"
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source "fs/Kconfig.binfmt"
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endmenu
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source "net/Kconfig"
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source "drivers/Kconfig"
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source "fs/Kconfig"
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source "arch/mn10300/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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source "arch/mn10300/oprofile/Kconfig"
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