menu "Kernel hacking"
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source "lib/Kconfig.debug"
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config DEBUG_VERBOSE
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bool "Verbose fault messages"
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default y
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select PRINTK
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help
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When a program crashes due to an exception, or the kernel detects
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an internal error, the kernel can print a not so brief message
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explaining what the problem was. This debugging information is
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useful to developers and kernel hackers when tracking down problems,
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but mostly meaningless to other people. This is always helpful for
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debugging but serves no purpose on a production system.
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Most people should say N here.
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config DEBUG_MMRS
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tristate "Generate Blackfin MMR tree"
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depends on !PINCTRL
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select DEBUG_FS
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help
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Create a tree of Blackfin MMRs via the debugfs tree. If
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you enable this, you will find all MMRs laid out in the
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/sys/kernel/debug/blackfin/ directory where you can read/write
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MMRs directly from userspace. This is obviously just a debug
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feature.
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config DEBUG_HWERR
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bool "Hardware error interrupt debugging"
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depends on DEBUG_KERNEL
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help
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When enabled, the hardware error interrupt is never disabled, and
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will happen immediately when an error condition occurs. This comes
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at a slight cost in code size, but is necessary if you are getting
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hardware error interrupts and need to know where they are coming
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from.
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config EXACT_HWERR
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bool "Try to make Hardware errors exact"
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depends on DEBUG_HWERR
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help
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By default, the Blackfin hardware errors are not exact - the error
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be reported multiple cycles after the error happens. This delay
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can cause the wrong application, or even the kernel to receive a
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signal to be killed. If you are getting HW errors in your system,
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try turning this on to ensure they are at least coming from the
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proper thread.
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On production systems, it is safe (and a small optimization) to say N.
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config DEBUG_DOUBLEFAULT
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bool "Debug Double Faults"
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default n
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help
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If an exception is caused while executing code within the exception
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handler, the NMI handler, the reset vector, or in emulator mode,
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a double fault occurs. On the Blackfin, this is a unrecoverable
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event. You have two options:
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- RESET exactly when double fault occurs. The excepting
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instruction address is stored in RETX, where the next kernel
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boot will print it out.
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- Print debug message. This is much more error prone, although
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easier to handle. It is error prone since:
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- The excepting instruction is not committed.
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- All writebacks from the instruction are prevented.
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- The generated exception is not taken.
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- The EXCAUSE field is updated with an unrecoverable event
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The only way to check this is to see if EXCAUSE contains the
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unrecoverable event value at every exception return. By selecting
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this option, you are skipping over the faulting instruction, and
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hoping things stay together enough to print out a debug message.
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This does add a little kernel code, but is the only method to debug
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double faults - if unsure say "Y"
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choice
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prompt "Double Fault Failure Method"
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default DEBUG_DOUBLEFAULT_PRINT
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depends on DEBUG_DOUBLEFAULT
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config DEBUG_DOUBLEFAULT_PRINT
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bool "Print"
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config DEBUG_DOUBLEFAULT_RESET
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bool "Reset"
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endchoice
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config DEBUG_HUNT_FOR_ZERO
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bool "Catch NULL pointer reads/writes"
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default y
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help
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Say Y here to catch reads/writes to anywhere in the memory range
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from 0x0000 - 0x0FFF (the first 4k) of memory. This is useful in
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catching common programming errors such as NULL pointer dereferences.
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Misbehaving applications will be killed (generate a SEGV) while the
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kernel will trigger a panic.
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Enabling this option will take up an extra entry in CPLB table.
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Otherwise, there is no extra overhead.
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config DEBUG_BFIN_HWTRACE_ON
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bool "Turn on Blackfin's Hardware Trace"
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default y
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help
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All Blackfins include a Trace Unit which stores a history of the last
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16 changes in program flow taken by the program sequencer. The history
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allows the user to recreate the program sequencer’s recent path. This
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can be handy when an application dies - we print out the execution
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path of how it got to the offending instruction.
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By turning this off, you may save a tiny amount of power.
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choice
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prompt "Omit loop Tracing"
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default DEBUG_BFIN_HWTRACE_COMPRESSION_OFF
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depends on DEBUG_BFIN_HWTRACE_ON
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help
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The trace buffer can be configured to omit recording of changes in
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program flow that match either the last entry or one of the last
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two entries. Omitting one of these entries from the record prevents
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the trace buffer from overflowing because of any sort of loop (for, do
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while, etc) in the program.
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Because zero-overhead Hardware loops are not recorded in the trace buffer,
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this feature can be used to prevent trace overflow from loops that
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are nested four deep.
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config DEBUG_BFIN_HWTRACE_COMPRESSION_OFF
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bool "Trace all Loops"
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help
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The trace buffer records all changes of flow
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config DEBUG_BFIN_HWTRACE_COMPRESSION_ONE
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bool "Compress single-level loops"
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help
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The trace buffer does not record single loops - helpful if trace
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is spinning on a while or do loop.
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config DEBUG_BFIN_HWTRACE_COMPRESSION_TWO
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bool "Compress two-level loops"
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help
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The trace buffer does not record loops two levels deep. Helpful if
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the trace is spinning in a nested loop
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endchoice
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config DEBUG_BFIN_HWTRACE_COMPRESSION
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int
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depends on DEBUG_BFIN_HWTRACE_ON
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default 0 if DEBUG_BFIN_HWTRACE_COMPRESSION_OFF
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default 1 if DEBUG_BFIN_HWTRACE_COMPRESSION_ONE
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default 2 if DEBUG_BFIN_HWTRACE_COMPRESSION_TWO
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config DEBUG_BFIN_HWTRACE_EXPAND
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bool "Expand Trace Buffer greater than 16 entries"
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depends on DEBUG_BFIN_HWTRACE_ON
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default n
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help
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By selecting this option, every time the 16 hardware entries in
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the Blackfin's HW Trace buffer are full, the kernel will move them
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into a software buffer, for dumping when there is an issue. This
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has a great impact on performance, (an interrupt every 16 change of
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flows) and should normally be turned off, except in those nasty
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debugging sessions
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config DEBUG_BFIN_HWTRACE_EXPAND_LEN
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int "Size of Trace buffer (in power of 2k)"
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range 0 4
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depends on DEBUG_BFIN_HWTRACE_EXPAND
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default 1
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help
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This sets the size of the software buffer that the trace information
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is kept in.
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0 for (2^0) 1k, or 256 entries,
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1 for (2^1) 2k, or 512 entries,
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2 for (2^2) 4k, or 1024 entries,
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3 for (2^3) 8k, or 2048 entries,
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4 for (2^4) 16k, or 4096 entries
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config DEBUG_BFIN_NO_KERN_HWTRACE
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bool "Turn off hwtrace in CPLB handlers"
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depends on DEBUG_BFIN_HWTRACE_ON
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default y
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help
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The CPLB error handler contains a lot of flow changes which can
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quickly fill up the hardware trace buffer. When debugging crashes,
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the hardware trace may indicate that the problem lies in kernel
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space when in reality an application is buggy.
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Say Y here to disable hardware tracing in some known "jumpy" pieces
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of code so that the trace buffer will extend further back.
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config EARLY_PRINTK
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bool "Early printk"
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default n
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select SERIAL_CORE_CONSOLE
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help
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This option enables special console drivers which allow the kernel
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to print messages very early in the bootup process.
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This is useful for kernel debugging when your machine crashes very
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early before the console code is initialized. After enabling this
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feature, you must add "earlyprintk=serial,uart0,57600" to the
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command line (bootargs). It is safe to say Y here in all cases, as
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all of this lives in the init section and is thrown away after the
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kernel boots completely.
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config NMI_WATCHDOG
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bool "Enable NMI watchdog to help debugging lockup on SMP"
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default n
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depends on SMP
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help
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If any CPU in the system does not execute the period local timer
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interrupt for more than 5 seconds, then the NMI handler dumps debug
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information. This information can be used to debug the lockup.
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config CPLB_INFO
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bool "Display the CPLB information"
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help
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Display the CPLB information via /proc/cplbinfo.
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config ACCESS_CHECK
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bool "Check the user pointer address"
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default y
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help
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Usually the pointer transfer from user space is checked to see if its
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address is in the kernel space.
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Say N here to disable that check to improve the performance.
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config BFIN_ISRAM_SELF_TEST
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bool "isram boot self tests"
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default n
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help
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Run some self tests of the isram driver code at boot.
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config BFIN_PSEUDODBG_INSNS
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bool "Support pseudo debug instructions"
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default n
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help
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This option allows the kernel to emulate some pseudo instructions which
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allow simulator test cases to be run under Linux with no changes.
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Most people should say N here.
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config BFIN_PM_WAKEUP_TIME_BENCH
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bool "Display the total time for kernel to resume from power saving mode"
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default n
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help
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Display the total time when kernel resumes normal from standby or
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suspend to mem mode.
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endmenu
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