When waiting for high frequency requests, the finite amount of time
required to set up the irq and wait upon it limits the response rate. By
busywaiting on the request completion for a short while we can service
the high frequency waits as quick as possible. However, if it is a slow
request, we want to sleep as quickly as possible. The tradeoff between
waiting and sleeping is roughly the time it takes to sleep on a request,
on the order of a microsecond. Based on measurements of synchronous
workloads from across big core and little atom, I have set the limit for
busywaiting as 10 microseconds. In most of the synchronous cases, we can
reduce the limit down to as little as 2 miscroseconds, but that leaves
quite a few test cases regressing by factors of 3 and more.
The code currently uses the jiffie clock, but that is far too coarse (on
the order of 10 milliseconds) and results in poor interactivity as the
CPU ends up being hogged by slow requests. To get microsecond resolution
we need to use a high resolution timer. The cheapest of which is polling
local_clock(), but that is only valid on the same CPU. If we switch CPUs
because the task was preempted, we can also use that as an indicator that
the system is too busy to waste cycles on spinning and we should sleep
instead.
__i915_spin_request was introduced in
commit 2def4ad99b [v4.2]
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue Apr 7 16:20:41 2015 +0100
drm/i915: Optimistically spin for the request completion
v2: Drop full u64 for unsigned long - the timer is 32bit wraparound safe,
so we can use native register sizes on smaller architectures. Mention
the approximate microseconds units for elapsed time and add some extra
comments describing the reason for busywaiting.
v3: Raise the limit to 10us
v4: Now 5us.
Reported-by: Jens Axboe <axboe@kernel.dk>
Link: https://lkml.org/lkml/2015/11/12/621
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: "Rogozhkin, Dmitry V" <dmitry.v.rogozhkin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Eero Tamminen <eero.t.tamminen@intel.com>
Cc: "Rantala, Valtteri" <valtteri.rantala@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1449833608-22125-3-git-send-email-chris@chris-wilson.co.uk
(cherry picked from commit ca5b721e23)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Pull RTC fixes from Alexandre Belloni:
"Late fixes for the RTC subsystem for 4.4:
A fix for a nasty hardware bug in rk808 and an initialization
reordering in da9063 to fix a possible crash"
* tag 'rtc-4.4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux:
rtc: da9063: fix access ordering error during RTC interrupt at system power on
rtc: rk808: Compensate for Rockchip calendar deviation on November 31st
This fix alters the ordering of the IRQ and device registrations in the RTC
driver probe function. This change will apply to the RTC driver that supports
both DA9063 and DA9062 PMICs.
A problem could occur with the existing RTC driver if:
A system is started from a cold boot using the PMIC RTC IRQ to initiate a
power on operation. For instance, if an RTC alarm is used to start a
platform from power off.
The existing driver IRQ is requested before the device has been properly
registered.
i.e.
ret = devm_request_threaded_irq()
comes before
rtc->rtc_dev = devm_rtc_device_register();
In this case, the interrupt can be called before the device has been
registered and the handler can be called immediately. The IRQ handler
da9063_alarm_event() contains the function call
rtc_update_irq(rtc->rtc_dev, 1, RTC_IRQF | RTC_AF);
which in turn tries to access the unavailable rtc->rtc_dev.
The fix is to reorder the functions inside the RTC probe. The IRQ is
requested after the RTC device resource has been registered so that
get_irq_byname is the last thing to happen.
Signed-off-by: Steve Twiss <stwiss.opensource@diasemi.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
In A.D. 1582 Pope Gregory XIII found that the existing Julian calendar
insufficiently represented reality, and changed the rules about
calculating leap years to account for this. Similarly, in A.D. 2013
Rockchip hardware engineers found that the new Gregorian calendar still
contained flaws, and that the month of November should be counted up to
31 days instead. Unfortunately it takes a long time for calendar changes
to gain widespread adoption, and just like more than 300 years went by
before the last Protestant nation implemented Greg's proposal, we will
have to wait a while until all religions and operating system kernels
acknowledge the inherent advantages of the Rockchip system. Until then
we need to translate dates read from (and written to) Rockchip hardware
back to the Gregorian format.
This patch works by defining Jan 1st, 2016 as the arbitrary anchor date
on which Rockchip and Gregorian calendars are in sync. From that we can
translate arbitrary later dates back and forth by counting the number
of November/December transitons since the anchor date to determine the
offset between the calendars. We choose this method (rather than trying
to regularly "correct" the date stored in hardware) since it's the only
way to ensure perfect time-keeping even if the system may be shut down
for an unknown number of years. The drawback is that other software
reading the same hardware (e.g. mainboard firmware) must use the same
translation convention (including the same anchor date) to be able to
read and write correct timestamps from/to the RTC.
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Pull tty/serial fixes from Greg KH:
"Here are some tty/serial driver fixes for 4.4-rc6 that resolve some
reported problems. All of these have been in linux-next. The details
are in the shortlog"
* tag 'tty-4.4-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
tty: Fix GPF in flush_to_ldisc()
serial: earlycon: Add missing spinlock initialization
serial: sh-sci: Fix length of scatterlist
n_tty: Fix poll() after buffer-limited eof push read
serial: 8250_uniphier: fix dl_read and dl_write functions
Pull USB fixes from Greg KH:
"Here are some USB and PHY fixes for 4.4-rc6. All of them resolve some
reported problems. Full details in the shortlog"
* tag 'usb-4.4-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
USB: fix invalid memory access in hub_activate()
USB: ipaq.c: fix a timeout loop
phy: core: Get a refcount to phy in devm_of_phy_get_by_index()
phy: cygnus: pcie: add missing of_node_put
phy: miphy365x: add missing of_node_put
phy: miphy28lp: add missing of_node_put
phy: rockchip-usb: add missing of_node_put
phy: berlin-sata: add missing of_node_put
phy: mt65xx-usb3: add missing of_node_put
phy: brcmstb-sata: add missing of_node_put
phy: sun9i-usb: add USB dependency
Pull md fixes from Neil Brown:
"Four fixes for md:
- two recently introduced regressions fixed.
- one older bug in RAID10 - tagged for -stable since 4.2
- one minor sysfs api improvement"
* tag 'md/4.4-rc5-fixes' of git://neil.brown.name/md:
Fix remove_and_add_spares removes drive added as spare in slot_store
md: fix bug due to nested suspend
MD: change journal disk role to disk 0
md/raid10: fix data corruption and crash during resync
Pull powerpc fixes from Michael Ellerman:
- Partial revert of "powerpc: Individual System V IPC system calls"
- pr_warn_once on unsupported OPAL_MSG type from Stewart
- Fix deadlock in opal-irqchip introduced by "Fix double endian
conversion" from Alistair
* tag 'powerpc-4.4-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/opal-irqchip: Fix deadlock introduced by "Fix double endian conversion"
powerpc/powernv: pr_warn_once on unsupported OPAL_MSG type
Partial revert of "powerpc: Individual System V IPC system calls"
Pull spi fixes from Mark Brown:
"A couple of reference counting bugs here, one in spidev and one with
holding an extra reference in the core that we never freed if we
removed a device, plus a driver specific fix. Both of the refcounting
bugs are very old but they've only been found by observation so
hopefully their impact has been low"
* tag 'spi-fix-v4.4-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi:
spi: fix parent-device reference leak
spi: spidev: Hold spi_lock over all defererences of spi in release()
spi-fsl-dspi: Fix CTAR Register access
Pull GPIO fixes from Linus Walleij:
"Some GPIO fixes for the v4.4 series. Most prominent: I revert the
error propagation from the .get() function until we can fix up all the
drivers properly for v4.5.
- Revert the error number propagation from the .get() vtable entry
temporarily, until we make the proper fixes to all drivers.
- Fix the clamping behaviour in the generic GPIO driver.
- Driver fix for the ath79 driver"
* tag 'gpio-v4.4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio:
gpio: revert get() to non-errorprogating behaviour
gpio: generic: clamp values from bgpio_get_set()
gpio: ath79: Fix the logic to clear offset bit of AR71XX_GPIO_REG_OE register
Pull pin control fixes from Linus Walleij:
- Driver fixes for Freescale i.MX7D, Intel, Broadcom 2835
- One MAINTAINERS entry
* tag 'pinctrl-v4.4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
MAINTAINERS: pinctrl: Add maintainers for pinctrl-single
pinctrl: bcm2835: Fix initial value for direction_output
pinctrl: intel: fix offset calculation issue of register PAD_OWN
pinctrl: intel: fix bug of register offset calculation
pinctrl: freescale: add ZERO_OFFSET_VALID flag for vf610 pinctrl
Pull i2c fixes from Wolfram Sang:
"A set of 'usual' driver bugfixes for the I2C subsystem"
* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
i2c: rcar: disable runtime PM correctly in slave mode
i2c: designware: Keep pm_runtime_enable/_disable calls in sync
i2c: designware: fix IO timeout issue for AMD controller
i2c: imx: init bus recovery info before adding i2c adapter
i2c: do not use 0x in front of %pa
i2c: davinci: Increase module clock frequency
i2c: mv64xxx: The n clockdiv factor is 0 based on sunxi SoCs
i2c: rk3x: populate correct variable for sda_falling_time
When we also are I2C slave, we need to disable runtime PM because the
address detection mechanism needs to be active all the time. However, we
can reenable runtime PM once the slave instance was unregistered. So,
use pm_runtime_get_sync/put to achieve this, since it has proper
refcounting. pm_runtime_allow/forbid is like a global knob controllable
from userspace which is unsuitable here.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
Pull power management fixes from Rafael Wysocki:
"These fix a potential regression introduced during the 4.3 cycle
(generic power domains framework), a nasty bug that has been present
forever (power capping RAPL driver), a build issue (Tegra cpufreq
driver) and a minor ugliness introduced recently (intel_pstate).
Specifics:
- Fix a potential regression in the generic power domains framework
introduced during the 4.3 development cycle that may lead to
spurious failures of system suspend in certain situations (Ulf
Hansson).
- Fix a problem in the power capping RAPL (Running Average Power
Limits) driver that causes it to initialize successfully on some
systems where it is not supposed to do that which is due to an
incorrect check in an initialization routine (Prarit Bhargava).
- Fix a build problem in the cpufreq Tegra driver that depends on the
regulator framework, but that dependency is not reflected in
Kconfig (Arnd Bergmann).
- Fix a recent mistake in the intel_pstate driver where a numeric
constant is used directly instead of a symbol defined specifically
for the case in question (Prarit Bhargava)"
* tag 'pm+acpi-4.4-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
powercap / RAPL: fix BIOS lock check
cpufreq: intel_pstate: Minor cleanup for FRAC_BITS
cpufreq: tegra: add regulator dependency for T124
PM / Domains: Allow runtime PM callbacks to be re-used during system PM
Pull SCSI fixes from James Bottomley:
"Three fixes this time, two in SES picked up by KASAN for various types
of buffer overrun. The first is a USB array which returns page 8
whatever is asked for and causes us to overrun with incorrect data
format assumptions and the second is an invalid iteration of page 10
(the additional information page).
The final fix is a reversion of a NULL deref fix which caused
suspend/resume not to be called in pairs leading to incorrect device
operation (Jens has queued a more proper fix for the problem in
block)"
* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
ses: fix additional element traversal bug
Revert "SCSI: Fix NULL pointer dereference in runtime PM"
ses: Fix problems with simple enclosures
When sending "SLEEP" command to the controller it ceases scanning
completely and is unable to wake the system up from sleep, so if it is
configured as a wakeup source we should simply configure interrupt for
wakeup and rely on idle logic within the controller to reduce power
consumption while it is not used.
Signed-off-by: James Chen <james.chen@emc.com.tw>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Pull media fixes from Mauro Carvalho Chehab.
* tag 'media/v4.4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
[media] airspy: increase USB control message buffer size
[media] hackrf: move RF gain ctrl enable behind module parameter
[media] hackrf: fix possible null ptr on debug printing
[media] Revert "[media] ivtv: avoid going past input/audio array"
Pull btrfs fixes from Chris Mason:
"A couple of small fixes"
* 'for-linus-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
Btrfs: check prepare_uptodate_page() error code earlier
Btrfs: check for empty bitmap list in setup_cluster_bitmaps
btrfs: fix misleading warning when space cache failed to load
Btrfs: fix transaction handle leak in balance
Btrfs: fix unprotected list move from unused_bgs to deleted_bgs list
Merge misc fixes from Andrew Morton:
"Three patches"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
include/linux/mmdebug.h: should include linux/bug.h
mm/zswap: change incorrect strncmp use to strcmp
proc: fix -ESRCH error when writing to /proc/$pid/coredump_filter
Chris Wilson
Matt Roper
Ville Syrjälä
Linus Torvalds
Steve Twiss
Julius Werner
Wolfram Sang
James Chen