linux-toradex.git/include/linux/math64.h, branch v6.0-rc1

math64: New DIV_U64_ROUND_CLOSEST helper

2022-02-25T09:27:57+00:00

Provide DIV_U64_ROUND_CLOSEST helper which uses div_u64 to perform
division rounded to the closest integer using unsigned 64bit
dividend and unsigned 32bit divisor.

Reviewed-by: Marek Behún 
Signed-off-by: Pali Rohár 
Signed-off-by: Marek Behún 
Link: https://lore.kernel.org/r/20220219152818.4319-2-kabel@kernel.org
Signed-off-by: Greg Kroah-Hartman

math64.h: Add mul_s64_u64_shr()

2021-06-17T17:09:27+00:00

This function is needed for KVM's nested virtualization. The nested TSC
scaling implementation requires multiplying the signed TSC offset with
the unsigned TSC multiplier.

Signed-off-by: Ilias Stamatis 
Reviewed-by: Maxim Levitsky 
Message-Id: <20210526184418.28881-2-ilstam@amazon.com>
Signed-off-by: Paolo Bonzini

math64.h: kernel-docs: Convert some markups into normal comments

2020-10-15T05:49:46+00:00

There are several functions at math64.h that are also
defined at div64.c. As both are included at kernel-api.rst,
Sphinx 3.x complains about symbol duplication:

	./lib/math/div64.c:73: WARNING: Duplicate C declaration, also defined in 'core-api/kernel-api'.
	Declaration is 'div_s64_rem'.
	./lib/math/div64.c:104: WARNING: Duplicate C declaration, also defined in 'core-api/kernel-api'.
	Declaration is 'div64_u64_rem'.
	./lib/math/div64.c:144: WARNING: Duplicate C declaration, also defined in 'core-api/kernel-api'.
	Declaration is 'div64_u64'.
	./lib/math/div64.c:172: WARNING: Duplicate C declaration, also defined in 'core-api/kernel-api'.
	Declaration is 'div64_s64'.

In order to avoid Sphinx warnings about duplication, change the kernel-doc
markups to just comments at math64.h.

Reviewed-by: Vincenzo Frascino 
Signed-off-by: Mauro Carvalho Chehab

Merge tag 'for-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply

2020-08-08T04:27:37+00:00

Pull power supply and reset updates from Sebastian Reichel:
 "Power-supply core:
   - add COOL/WARM/HOT state from JEITA JISC8712:2015 specification
   - convert simple-battery DT binding to YAML
   - add long-life charging mode

 Battery/charger drivers:
   - bq25150: new charger driver
   - bq27xxx: add support for BQ27z561 and BQ28z610
   - max17040: support CAPACITY_ALERT_MIN
   - sbs-battery: add PEC support
   - wilco-ec: support long-life charging mode
   - bq25890: fix DT binding
   - misc. fixes and cleanups

 Reset drivers:
   - linkstation: new reset driver"

* tag 'for-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply: (32 commits)
  power: supply: wilco_ec: Add long life charging mode
  power: supply: bq27xxx_battery: Add the BQ28z610 Battery monitor
  dt-bindings: power: Add BQ28z610 compatible
  power: supply: bq27xxx_battery: Add the BQ27Z561 Battery monitor
  dt-bindings: power: Add BQ27Z561 compatible
  power: supply: test_power: Fix battery_current initial value
  power: supply: Fix kerneldoc of power_supply_temp2resist_simple()
  power: supply: cpcap-battery: Fix kerneldoc of cpcap_battery_read_accumulated()
  dt-bindings: power: Convert battery.txt to battery.yaml
  power: supply: rt5033_battery: Fix error code in rt5033_battery_probe()
  power: supply: max17040: Add POWER_SUPPLY_PROP_CAPACITY_ALERT_MIN
  power: supply: check if calc_soc succeeded in pm860x_init_battery
  power: supply: bq2xxxx: Replace HTTP links with HTTPS ones
  power: reset: add driver for LinkStation power off
  power: supply: sc27xx: prevent adc * 1000 from overflow
  math64: New DIV_S64_ROUND_CLOSEST helper
  power: fix duplicated words in bq2415x_charger.h
  power: Convert to DEFINE_SHOW_ATTRIBUTE
  power: reset: keystone-reset: Replace HTTP links with HTTPS ones
  power: supply: bq25150 introduce the bq25150
  ...

math64: New DIV_S64_ROUND_CLOSEST helper

2020-07-27T22:47:18+00:00

Provide DIV_S64_ROUND_CLOSEST helper which uses div_s64 to perform
division rounded to the closest integer using signed 64bit
dividend and signed 32bit divisor.

Signed-off-by: Chunyan Zhang 
Signed-off-by: Sebastian Reichel

sched/cputime: Improve cputime_adjust()

2020-06-15T12:10:00+00:00

People report that utime and stime from /proc//stat become very
wrong when the numbers are big enough, especially if you watch these
counters incrementally.

Specifically, the current implementation of: stime*rtime/total,
results in a saw-tooth function on top of the desired line, where the
teeth grow in size the larger the values become. IOW, it has a
relative error.

The result is that, when watching incrementally as time progresses
(for large values), we'll see periods of pure stime or utime increase,
irrespective of the actual ratio we're striving for.

Replace scale_stime() with a math64.h helper: mul_u64_u64_div_u64()
that is far more accurate. This also allows architectures to override
the implementation -- for instance they can opt for the old algorithm
if this new one turns out to be too expensive for them.

Signed-off-by: Oleg Nesterov 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20200519172506.GA317395@hirez.programming.kicks-ass.net

linux/math64.h: Extract common header for vDSO

2020-03-21T14:23:56+00:00

The vDSO library should only include the necessary headers required for
a userspace library (UAPI and a minimal set of kernel headers). To make
this possible it is necessary to isolate from the kernel headers the
common parts that are strictly necessary to build the library.

Split math64.h into linux and common headers to make the latter suitable
for inclusion in the vDSO library.

Signed-off-by: Vincenzo Frascino 
Signed-off-by: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20200320145351.32292-10-vincenzo.frascino@arm.com

math64: New DIV64_U64_ROUND_CLOSEST helper

2019-04-02T07:50:48+00:00

Provide DIV64_U64_ROUND_CLOSEST helper which performs division rounded to
the closest integer using an unsigned 64bit dividend and divisor.

This will be used in a follow-up patch to allow calculation of clock
divisors with high frequency parents in the R-Car Gen3 CPG MSSR driver
where overflow occurs if either the dividend or divisor is 32bit.

Signed-off-by: Simon Horman 
Signed-off-by: Geert Uytterhoeven

mm: don't miss the last page because of round-off error

2018-10-26T23:25:19+00:00

I've noticed, that dying memory cgroups are often pinned in memory by a
single pagecache page.  Even under moderate memory pressure they sometimes
stayed in such state for a long time.  That looked strange.

My investigation showed that the problem is caused by applying the LRU
pressure balancing math:

  scan = div64_u64(scan * fraction[lru], denominator),

where

  denominator = fraction[anon] + fraction[file] + 1.

Because fraction[lru] is always less than denominator, if the initial scan
size is 1, the result is always 0.

This means the last page is not scanned and has
no chances to be reclaimed.

Fix this by rounding up the result of the division.

In practice this change significantly improves the speed of dying cgroups
reclaim.

[guro@fb.com: prevent double calculation of DIV64_U64_ROUND_UP() arguments]
  Link: http://lkml.kernel.org/r/20180829213311.GA13501@castle
Link: http://lkml.kernel.org/r/20180827162621.30187-3-guro@fb.com
Signed-off-by: Roman Gushchin 
Reviewed-by: Andrew Morton 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Tejun Heo 
Cc: Rik van Riel 
Cc: Konstantin Khlebnikov 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'docs-4.15' of git://git.lwn.net/linux

2017-11-13T16:25:06+00:00

Pull documentation updates from Jonathan Corbet:
 "A relatively calm cycle for the docs tree again.

  - The old driver statement has been added to the kernel docs.

  - We have a couple of new helper scripts. find-unused-docs.sh from
    Sayli Karnic will point out kerneldoc comments that are not actually
    used in the documentation. Jani Nikula's
    documentation-file-ref-check finds references to non-existing files.

  - A new ftrace document from Steve Rostedt.

  - Vinod Koul converted the dmaengine docs to RST

  Beyond that, it's mostly simple fixes.

  This set reaches outside of Documentation/ a bit more than most. In
  all cases, the changes are to comment docs, mostly from Randy, in
  places where there didn't seem to be anybody better to take them"

* tag 'docs-4.15' of git://git.lwn.net/linux: (52 commits)
  documentation: fb: update list of available compiled-in fonts
  MAINTAINERS: update DMAengine documentation location
  dmaengine: doc: ReSTize pxa_dma doc
  dmaengine: doc: ReSTize dmatest doc
  dmaengine: doc: ReSTize client API doc
  dmaengine: doc: ReSTize provider doc
  dmaengine: doc: Add ReST style dmaengine document
  ftrace/docs: Add documentation on how to use ftrace from within the kernel
  bug-hunting.rst: Fix an example and a typo in a Sphinx tag
  scripts: Add a script to find unused documentation
  samples: Convert timers to use timer_setup()
  documentation: kernel-api: add more info on bitmap functions
  Documentation: fix selftests related file refs
  Documentation: fix ref to power basic-pm-debugging
  Documentation: fix ref to trace stm content
  Documentation: fix ref to coccinelle content
  Documentation: fix ref to workqueue content
  Documentation: fix ref to sphinx/kerneldoc.py
  Documentation: fix locking rt-mutex doc refs
  docs: dev-tools: correct Coccinelle version number
  ...