Add driver for the RTC hardware block on the Conexant CX92755 SoC, from
the Digicolor series of SoCs. Tested on the Equinox evaluation board for
the CX92755 chip.
[akpm@linux-foundation.org: build command arrays at compile-time]
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a device tree binding documentation to the Real Time Clock hardware
block on the Conexant CX92755 SoC. The CX92755 is from the Digicolor SoCs
series. Other SoCs in that series may share the same hardware block.
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When the clock is disabled, do not return a rate of 0 but instead return
the rate the clock will be running at after it gets enabled. This
prevents problems when the core clock code is trying to determine a
suitable rate, while the clock is still off.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The RTC is in a different clock domain so a quick read after write
can retrieve a mangled value of the old/new values
Signed-off-by: Adam Ward <adam.ward.opensource@diasemi.com>
Tested-by: Adam Ward <adam.ward.opensource@diasemi.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix two minor sparse warnings:
CHECK drivers/rtc/rtc-ds1685.c
drivers/rtc/rtc-ds1685.c:2178:1: warning: function 'ds1685_rtc_poweroff' with external linkage has definition
drivers/rtc/rtc-ds1685.c:802:23: warning: Using plain integer as NULL pointer
Fixes: aaaf5fbf56 ("rtc: add driver for DS1685 family of real time clocks")
Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The rtc driver core now sets the platform_driver 'owner' property, so
remove the assignment from the DS1685 driver.
Fixes: aaaf5fbf56: "rtc: add driver for DS1685 family of real time clocks"
Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The regmap_config struct may be const because it is not modified by the
driver and regmap_init() accepts pointer to const.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The current functions in s3c-rtc driver execute clk_enable/disable() to
control clocks and some functions execute s3c_rtc_alarm_clk_enable()
unnecessarily. So this patch deletes the duplicate clock control and
spilts s3c_rtc_alarm_clk_enable() out as
s3c_rtc_enable_clk()/s3c_rtc_disable_clk() to improve readability.
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When using device trees on the ARM platform, it is not certain at compile
time whether or not the system will have a RTC.
If one enables CONFIG_HCTOSYS just in case the system booted has a RTC,
and it turns out not to be, this will result in a big fat "unable to open
rtc device" error being printed to console, even when "quiet" is set in
the kernel cmdline.
Fix this by outputting the message with loglevel info instead.
Signed-off-by: Floris Bos <bos@je-eigen-domein.nl>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Despite its name, sign_extend32() is safe to use for 8 bit types too.
(See https://lkml.org/lkml/2015/1/18/289).
Signed-off-by: Martin Kepplinger <martink@posteo.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Set the of_match_table for this driver so that devices can be described in
the device tree. This device is used in the Trimslice and is already
defined in the Trimslice device tree.
Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Cc: Mike Rapoport <mike@compulab.co.il>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The rtc's status register allows to determine if a 32k crystal is
connected to keep the rtc running in low power states provided the
corresponding fuse bits were blown correctly during production. (In case
they were not, the right frequency can be stated in the device tree.) If
there is no such crystal available force the 24 MHz XTAL clock to keep
running to retain the right date and time. Otherwise use the crystal to
save some power.
It would be nice to only switch to the crystal when the XTAL clock is
about to be disabled and keep the crystal off when unneeded because XTAL
is always on while the chip is powered on. But as sudden power loss isn't
detectable this is not save.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit does not change any logic here. It just makes the code easier
to read.
This is how it looked like:
If err != 0 return err;
else return 0;
Signed-off-by: Robert Kmiec <robert.r.kmiec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It might be annoying to constantly see this:
scripts/Makefile.kasan:16: Cannot use CONFIG_KASAN: -fsanitize=kernel-address is not supported by compiler
while performing allmodconfig/allyesconfig build tests.
Disable this warning if CONFIG_COMPILE_TEST=y.
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
sprintf() reliably returns the number of characters printed, so we don't
need to ask strlen() where we are. Also replace calling sprintf("%02x")
in a loop with the much simpler bin2hex().
[akpm@linux-foundation.org: it's odd to include kernel.h after everything else]
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit 1f65f947a6 ("checkpatch: add checks for question mark and
colon spacing") back in 2008, checkpatch has reported false positive for
asm volatile uses of "::" checkpatch thinks colons should always have
spaces around it.
Add an exception for colons with colons on either side for this valid asm
volatile (and c++) use.
Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Yehuda Yitschak <yehuday@marvell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If a patch touches multiple files, the --fix and --fix-inplace option
doesn't keep the proper line count and makes the new patch file not able
to be applied via bad offset line numbers when lines are added or deleted
by the --fix option.
Dunno how that extra backslash snuck in there.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ENOSYS is the mechanism used by user code to detect whether the running
kernel implements a given system call. It should not be returned by
anything except an unimplemented system call.
Unfortunately, it is rather frequently used in the kernel to indicate that
various new functions of existing system calls are not implemented. This
should be discouraged.
Improve the comment in errno.h to help clarify ENOSYS's purpose.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ENOSYS means that a nonexistent system call was called. We have a
bad habit of using it for things like invalid operations on
otherwise valid syscalls. We should avoid this in new code.
Pervasive incorrect usage of ENOSYS came up at the kernel summit ABI
review discussion. Let's see if checkpatch can help.
I'll submit a separate patch for include/uapi/asm-generic/errno.h.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
const objects shouldn't be __read_mostly. They are read-only.
Marking these objects as __read_mostly causes section conflicts with LTO
linking.
So add a test to try to avoid this issue.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Code such as:
x = timercmp(&now, &end, <);
Will currently trigger a checkpatch error. e.g.
ERROR: spaces required around that '<'
This is because the "Ignore operators passed as parameters" check looks
only for a comma following the operator. Improve the check by also
looking for a close parenthesis.
Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a test for sizeof(foo)/sizeof(foo[0]) that could be ARRAY_SIZE(foo).
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add another struct to the list of normally const struct types
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are #defines with long string constants like:
#define foo "some really long string > 80 columns"
Add a long line exception for them.
Miscellanea:
Use the $String variable for slightly better readability
Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Madalin-Cristian Bucur <madalin.bucur@freescale.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit messages lines are sometimes overly long.
Suggest line wrapping at 75 columns so the default git commit log
indentation of 4 plus the commit message text still fits on an 80 column
screen.
Add a checkpatch test for long commit messages lines too.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: David Miller <davem@davemloft.net>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ian Morris <ipm@chirality.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently checkpatch warns when asm/file.h is included and linux/file.h
exists. That conversion can be made when linux/file.h includes asm/file.h
which is not always the case.(See signal.h)
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Andy Whitcroft <apw@canonical.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Using 'const <type> const *' is generally meant to be written 'const
<type> * const'.
Add a test for the miswritten form.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a few conditions to the test to find
return (ERRNO);
Make the output message a bit less cryptic too.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently checkpatch will fuss if one uses world writable settings in
debugfs files and DEVICE_ATTR uses by testing S_IWUGO but not testing
S_IWOTH, S_IRWXUGO or S_IALLUGO.
Extend the check to catch all cases exporting world writable permissions
including octal values.
[akpm@linux-foundation.org: remove stray $]
Signed-off-by: Joe Perches <joe@perches.com>
Original-patch-by: Nicholas Mc Guire <hofrat@osadl.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If a codespell dictionary exists, use it if desired. default is off,
maybe it could be turned on later.
codespell's dictionary format allows multiple possible corrections, ignore
that for now and only use the first suggestion.
Also add \b to spelling test so that consecutive misspelled words
are found properly.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Masanari Iida <standby24x7@gmail.com>
Cc: Lucas De Marchi <lucas.de.marchi@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Only commit log and patch additions are checked for typos and spelling
errors currently. Add a check of the email subject line too.
Signed-off-by: Joe Perches <joe@perches.com>
Suggested-by: Jani Nikula <jani.nikula@linux.intel.com>
Tested-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The "no space is necessary after a cast" sizeof exclusion doesn't work
properly.
The test reports a false positive for code like:
BUILD_BUG_ON(sizeof(struct batadv_bla_claim_dst) != 6);
Make it work, simplify the exclusions, and add some comments.
Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 2473238eac ("ihex: add support for CS:IP/EIP records") removes
the "default:" statement in the switch block, making the "return
usage();" line dead code and ihex2fw silently ignoring unknown options.
Restore this statement.
This bug was found by building with HOSTCC=clang and adding
-Wunreachable-code-return to HOSTCFLAGS.
Fixes: 2473238eac ("ihex: add support for CS:IP/EIP records")
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
bitmap_empty() has its own implementation. But it's clearly as simple as:
find_first_bit(src, nbits) == nbits
The same is true for 'bitmap_full'.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Cc: George Spelvin <linux@horizon.com>
Cc: Alexey Klimov <klimov.linux@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that the kernel provides DIV_ROUND_CLOSEST_ULL(), drop the internal
implementation and use the kernel one.
Signed-off-by: Javi Merino <javi.merino@arm.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Peter Rosin <peda@axentia.se>
Acked-by: Mark Brown <broonie@kernel.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that the kernel provides DIV_ROUND_CLOSEST_ULL(), drop the internal
implementation and use the kernel one.
Signed-off-by: Javi Merino <javi.merino@arm.com>
Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Acked-by: Antti Palosaari <crope@iki.fi>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that the kernel provides DIV_ROUND_CLOSEST_ULL(), drop the internal
implementation and use the kernel one.
Signed-off-by: Javi Merino <javi.merino@arm.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that the kernel provides DIV_ROUND_CLOSEST_ULL(), drop the internal
implementation and use the kernel one.
Signed-off-by: Javi Merino <javi.merino@arm.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Alex Elder <elder@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have grown a number of different implementations of
DIV_ROUND_CLOSEST_ULL throughout the kernel. Move the i915 one to
kernel.h so that it can be reused.
Signed-off-by: Javi Merino <javi.merino@arm.com>
Reviewed-by: Jeff Epler <jepler@unpythonic.net>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Guenter Roeck <linux@roeck-us.net>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Alex Elder <elder@linaro.org>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Javi Merino <javi.merino@arm.com>
Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I hadn't had enough coffee when I wrote this. Currently, the final
increment of buf depends on the value loaded from the table, and
causes gcc to emit a cmov immediately before the return. It is smarter
to let it depend on r, since the increment can then be computed in
parallel with the final load/store pair. It also shaves 16 bytes of
.text.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Replace the loop iterating over pwm_freq_cksel0 with a call to
find_closest_descending().
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use find_closest() to locate the closest average in ina226_avg_tab.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This series unduplicates the code used to find the member in an array
closest to 'x'.
The first patch adds a macro implementing the algorithm in two flavors -
for arrays sorted in ascending and descending order. The second updates
Documentation/CodingStyle on the naming convention for local variables in
macros resembling functions. Other three patches replace duplicated code
with calls to one of these macros in some hwmon drivers.
This patch (of 5):
Searching for the member of an array closest to 'x' is duplicated in
several places.
Add a new include - util_macros.h - and two macros that implement this
algorithm for arrays sorted both in ascending and descending order.
Uses linear search.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
bucket_find_contain() will search the bucket list for a dma_debug_entry.
When the entry isn't found it needs to search other buckets too, since
only the start address of a dma range is hashed (which might be in a
different bucket).
A copy of the dma_debug_entry is used to get the previous hash bucket
but when its list is searched the original dma_debug_entry is to be used
not its modified copy.
This fixes false "device driver tries to sync DMA memory it has not allocated"
warnings.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Horia Geanta <horia.geanta@freescale.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The most expensive part of decimal conversion is the divisions by 10
(albeit done using reciprocal multiplication with appropriately chosen
constants). I decided to see if one could eliminate around half of
these multiplications by emitting two digits at a time, at the cost of a
200 byte lookup table, and it does indeed seem like there is something
to be gained, especially on 64 bits. Microbenchmarking shows
improvements ranging from -50% (for numbers uniformly distributed in [0,
2^64-1]) to -25% (for numbers heavily biased toward the smaller end, a
more realistic distribution).
On a larger scale, perf shows that top, one of the big consumers of /proc
data, uses 0.5-1.0% fewer cpu cycles.
I had to jump through some hoops to get the 32 bit code to compile and run
on my 64 bit machine, so I'm not sure how relevant these numbers are, but
just for comparison the microbenchmark showed improvements between -30%
and -10%.
The bloat-o-meter costs are around 150 bytes (the generated code is a
little smaller, so it's not the full 200 bytes) on both 32 and 64 bit.
I'm aware that extra cache misses won't show up in a microbenchmark as
used above, but on the other hand decimal conversions often happen in bulk
(for example in the case of top).
I have of course tested that the new code generates the same output as the
old, for both the first and last 1e10 numbers in [0,2^64-1] and 4e9
'random' numbers in-between.
Test and verification code on github: https://github.com/Villemoes/dec.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Tested-by: Jeff Epler <jepler@unpythonic.net>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
