android_kernel_xiaomi_sm8350/arch/frv/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.
#
config FRV
bool
default y
config ZONE_DMA
bool
default y
config RWSEM_GENERIC_SPINLOCK
bool
default y
config RWSEM_XCHGADD_ALGORITHM
bool
config GENERIC_FIND_NEXT_BIT
bool
default y
config GENERIC_HWEIGHT
bool
default y
config GENERIC_CALIBRATE_DELAY
bool
default n
config GENERIC_HARDIRQS
bool
default y
config GENERIC_HARDIRQS_NO__DO_IRQ
bool
default y
config GENERIC_TIME
bool
default y
config TIME_LOW_RES
bool
default y
config QUICKLIST
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default y
config ARCH_HAS_ILOG2_U64
bool
default y
config HZ
int
default 1000
mainmenu "Fujitsu FR-V Kernel Configuration"
source "init/Kconfig"
menu "Fujitsu FR-V system setup"
config MMU
bool "MMU support"
help
This options switches on and off support for the FR-V MMU
(effectively switching between vmlinux and uClinux). Not all FR-V
CPUs support this. Currently only the FR451 has a sufficiently
featured MMU.
config FRV_OUTOFLINE_ATOMIC_OPS
bool "Out-of-line the FRV atomic operations"
default n
help
Setting this option causes the FR-V atomic operations to be mostly
implemented out-of-line.
See Documentation/frv/atomic-ops.txt for more information.
config HIGHMEM
bool "High memory support"
depends on MMU
default y
help
If you wish to use more than 256MB of memory with your MMU based
system, you will need to select this option. The kernel can only see
the memory between 0xC0000000 and 0xD0000000 directly... everything
else must be kmapped.
The arch is, however, capable of supporting up to 3GB of SDRAM.
config HIGHPTE
bool "Allocate page tables in highmem"
depends on HIGHMEM
default y
help
The VM uses one page of memory for each page table. For systems
with a lot of RAM, this can be wasteful of precious low memory.
Setting this option will put user-space page tables in high memory.
source "mm/Kconfig"
choice
prompt "uClinux kernel load address"
depends on !MMU
default UCPAGE_OFFSET_C0000000
help
This option sets the base address for the uClinux kernel. The kernel
will rearrange the SDRAM layout to start at this address, and move
itself to start there. It must be greater than 0, and it must be
sufficiently less than 0xE0000000 that the SDRAM does not intersect
the I/O region.
The base address must also be aligned such that the SDRAM controller
can decode it. For instance, a 512MB SDRAM bank must be 512MB aligned.
config UCPAGE_OFFSET_20000000
bool "0x20000000"
config UCPAGE_OFFSET_40000000
bool "0x40000000"
config UCPAGE_OFFSET_60000000
bool "0x60000000"
config UCPAGE_OFFSET_80000000
bool "0x80000000"
config UCPAGE_OFFSET_A0000000
bool "0xA0000000"
config UCPAGE_OFFSET_C0000000
bool "0xC0000000 (Recommended)"
endchoice
config PAGE_OFFSET
hex
default 0x20000000 if UCPAGE_OFFSET_20000000
default 0x40000000 if UCPAGE_OFFSET_40000000
default 0x60000000 if UCPAGE_OFFSET_60000000
default 0x80000000 if UCPAGE_OFFSET_80000000
default 0xA0000000 if UCPAGE_OFFSET_A0000000
default 0xC0000000
config PROTECT_KERNEL
bool "Protect core kernel against userspace"
depends on !MMU
default y
help
Selecting this option causes the uClinux kernel to change the
permittivity of DAMPR register covering the core kernel image to
prevent userspace accessing the underlying memory directly.
choice
prompt "CPU Caching mode"
default FRV_DEFL_CACHE_WBACK
help
This option determines the default caching mode for the kernel.
Write-Back caching mode involves the all reads and writes causing
the affected cacheline to be read into the cache first before being
operated upon. Memory is not then updated by a write until the cache
is filled and a cacheline needs to be displaced from the cache to
make room. Only at that point is it written back.
Write-Behind caching is similar to Write-Back caching, except that a
write won't fetch a cacheline into the cache if there isn't already
one there; it will write directly to memory instead.
Write-Through caching only fetches cachelines from memory on a
read. Writes always get written directly to memory. If the affected
cacheline is also in cache, it will be updated too.
The final option is to turn of caching entirely.
Note that not all CPUs support Write-Behind caching. If the CPU on
which the kernel is running doesn't, it'll fall back to Write-Back
caching.
config FRV_DEFL_CACHE_WBACK
bool "Write-Back"
config FRV_DEFL_CACHE_WBEHIND
bool "Write-Behind"
config FRV_DEFL_CACHE_WTHRU
bool "Write-Through"
config FRV_DEFL_CACHE_DISABLED
bool "Disabled"
endchoice
menu "CPU core support"
config CPU_FR401
bool "Include FR401 core support"
depends on !MMU
default y
help
This enables support for the FR401, FR401A and FR403 CPUs
config CPU_FR405
bool "Include FR405 core support"
depends on !MMU
default y
help
This enables support for the FR405 CPU
config CPU_FR451
bool "Include FR451 core support"
default y
help
This enables support for the FR451 CPU
config CPU_FR451_COMPILE
bool "Specifically compile for FR451 core"
depends on CPU_FR451 && !CPU_FR401 && !CPU_FR405 && !CPU_FR551
default y
help
This causes appropriate flags to be passed to the compiler to
optimise for the FR451 CPU
config CPU_FR551
bool "Include FR551 core support"
depends on !MMU
default y
help
This enables support for the FR555 CPU
config CPU_FR551_COMPILE
bool "Specifically compile for FR551 core"
depends on CPU_FR551 && !CPU_FR401 && !CPU_FR405 && !CPU_FR451
default y
help
This causes appropriate flags to be passed to the compiler to
optimise for the FR555 CPU
config FRV_L1_CACHE_SHIFT
int
default "5" if CPU_FR401 || CPU_FR405 || CPU_FR451
default "6" if CPU_FR551
endmenu
choice
prompt "System support"
default MB93091_VDK
config MB93091_VDK
bool "MB93091 CPU board with or without motherboard"
config MB93093_PDK
bool "MB93093 PDK unit"
endchoice
if MB93091_VDK
choice
prompt "Motherboard support"
default MB93090_MB00
config MB93090_MB00
bool "Use the MB93090-MB00 motherboard"
help
Select this option if the MB93091 CPU board is going to be used with
a MB93090-MB00 VDK motherboard
config MB93091_NO_MB
bool "Use standalone"
help
Select this option if the MB93091 CPU board is going to be used
without a motherboard
endchoice
endif
config FUJITSU_MB93493
bool "MB93493 Multimedia chip"
help
Select this option if the MB93493 multimedia chip is going to be
used.
choice
prompt "GP-Relative data support"
default GPREL_DATA_8
help
This option controls what data, if any, should be placed in the GP
relative data sections. Using this means that the compiler can
generate accesses to the data using GR16-relative addressing which
is faster than absolute instructions and saves space (2 instructions
per access).
However, the GPREL region is limited in size because the immediate
value used in the load and store instructions is limited to a 12-bit
signed number.
So if the linker starts complaining that accesses to GPREL data are
out of range, try changing this option from the default.
Note that modules will always be compiled with this feature disabled
as the module data will not be in range of the GP base address.
config GPREL_DATA_8
bool "Put data objects of up to 8 bytes into GP-REL"
config GPREL_DATA_4
bool "Put data objects of up to 4 bytes into GP-REL"
config GPREL_DATA_NONE
bool "Don't use GP-REL"
endchoice
config FRV_ONCPU_SERIAL
bool "Use on-CPU serial ports"
select SERIAL_8250
default y
config PCI
bool "Use PCI"
depends on MB93090_MB00
default y
help
Some FR-V systems (such as the MB93090-MB00 VDK) have PCI
onboard. If you have one of these boards and you wish to use the PCI
facilities, say Y here.
config RESERVE_DMA_COHERENT
bool "Reserve DMA coherent memory"
depends on PCI && !MMU
default y
help
Many PCI drivers require access to uncached memory for DMA device
communications (such as is done with some Ethernet buffer rings). If
a fully featured MMU is available, this can be done through page
table settings, but if not, a region has to be set aside and marked
with a special DAMPR register.
Setting this option causes uClinux to set aside a portion of the
available memory for use in this manner. The memory will then be
unavailable for normal kernel use.
source "drivers/pci/Kconfig"
source "drivers/pcmcia/Kconfig"
#config MATH_EMULATION
# bool "Math emulation support (EXPERIMENTAL)"
# depends on EXPERIMENTAL
# help
# At some point in the future, this will cause floating-point math
# instructions to be emulated by the kernel on machines that lack a
# floating-point math coprocessor. Thrill-seekers and chronically
# sleep-deprived psychotic hacker types can say Y now, everyone else
# should probably wait a while.
menu "Power management options"
config ARCH_SUSPEND_POSSIBLE
def_bool y
depends on !SMP
source kernel/power/Kconfig
endmenu
endmenu
menu "Executable formats"
source "fs/Kconfig.binfmt"
endmenu
source "net/Kconfig"
source "drivers/Kconfig"
source "fs/Kconfig"
source "arch/frv/Kconfig.debug"
source "security/Kconfig"
source "crypto/Kconfig"
source "lib/Kconfig"