<feed xmlns='http://www.w3.org/2005/Atom'>
<title>lwn.git/arch/arm/mach-omap2, branch docs-5.2a-merge</title>
<subtitle>Linux kernel documentation tree maintained by Jonathan Corbet</subtitle>
<id>http://mirrors.hust.edu.cn/git/lwn.git/atom?h=docs-5.2a-merge</id>
<link rel='self' href='http://mirrors.hust.edu.cn/git/lwn.git/atom?h=docs-5.2a-merge'/>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/'/>
<updated>2019-03-22T22:30:32+00:00</updated>
<entry>
<title>ARM: OMAP2+: add missing of_node_put after of_device_is_available</title>
<updated>2019-03-22T22:30:32+00:00</updated>
<author>
<name>Julia Lawall</name>
<email>Julia.Lawall@lip6.fr</email>
</author>
<published>2019-02-23T13:20:42+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=30645307e5d2c8a4caf978558c66121ac91ad17e'/>
<id>urn:sha1:30645307e5d2c8a4caf978558c66121ac91ad17e</id>
<content type='text'>
Add an of_node_put when a tested device node is not available.

The semantic patch that fixes this problem is as follows
(http://coccinelle.lip6.fr):

// &lt;smpl&gt;
@@
identifier f;
local idexpression e;
expression x;
@@

e = f(...);
... when != of_node_put(e)
    when != x = e
    when != e = x
    when any
if (&lt;+...of_device_is_available(e)...+&gt;) {
  ... when != of_node_put(e)
(
  return e;
|
+ of_node_put(e);
  return ...;
)
}
// &lt;/smpl&gt;

Fixes: e0c827aca0730 ("drm/omap: Populate DSS children in omapdss driver")
Signed-off-by: Julia Lawall &lt;Julia.Lawall@lip6.fr&gt;
Signed-off-by: Tony Lindgren &lt;tony@atomide.com&gt;
</content>
</entry>
<entry>
<title>Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm</title>
<updated>2019-03-15T21:37:46+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-03-15T21:37:46+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=0be288630752e6358d02eba7b283c1783a5c7c38'/>
<id>urn:sha1:0be288630752e6358d02eba7b283c1783a5c7c38</id>
<content type='text'>
Pull ARM updates from Russell King:

 - An improvement from Ard Biesheuvel, who noted that the identity map
   setup was taking a long time due to flush_cache_louis().

 - Update a comment about dma_ops from Wolfram Sang.

 - Remove use of "-p" with ld, where this flag has been a no-op since
   2004.

 - Remove the printing of the virtual memory layout, which is no longer
   useful since we hide pointers.

 - Correct SCU help text.

 - Remove legacy TWD registration method.

 - Add pgprot_device() implementation for mapping PCI sysfs resource
   files.

 - Initialise PFN limits earlier for kmemleak.

 - Fix argument count to match macro definition (affects clang builds)

 - Use unified assembler language almost everywhere for clang, and other
   clang improvements (from Stefan Agner, Nathan Chancellor).

 - Support security extension for noMMU and other noMMU cleanups (from
   Vladimir Murzin).

 - Remove unnecessary SMP bringup code (which was incorrectly copy'n'
   pasted from the ARM platform implementations) and remove it from the
   arch code to discourge further copys of it appearing.

 - Add Cortex A9 erratum preventing kexec working on some SoCs.

 - AMBA bus identification updates from Mike Leach.

 - More use of raw spinlocks to avoid -RT kernel issues (from Yang Shi
   and Sebastian Andrzej Siewior).

 - MCPM hyp/svc mode mismatch fixes from Marek Szyprowski.

* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm: (32 commits)
  ARM: 8849/1: NOMMU: Fix encodings for PMSAv8's PRBAR4/PRLAR4
  ARM: 8848/1: virt: Align GIC version check with arm64 counterpart
  ARM: 8847/1: pm: fix HYP/SVC mode mismatch when MCPM is used
  ARM: 8845/1: use unified assembler in c files
  ARM: 8844/1: use unified assembler in assembly files
  ARM: 8843/1: use unified assembler in headers
  ARM: 8841/1: use unified assembler in macros
  ARM: 8840/1: use a raw_spinlock_t in unwind
  ARM: 8839/1: kprobe: make patch_lock a raw_spinlock_t
  ARM: 8837/1: coresight: etmv4: Update ID register table to add UCI support
  ARM: 8836/1: drivers: amba: Update component matching to use the CoreSight UCI values.
  ARM: 8838/1: drivers: amba: Updates to component identification for driver matching.
  ARM: 8833/1: Ensure that NEON code always compiles with Clang
  ARM: avoid Cortex-A9 livelock on tight dmb loops
  ARM: smp: remove arch-provided "pen_release"
  ARM: actions: remove boot_lock and pen_release
  ARM: oxnas: remove CPU hotplug implementation
  ARM: qcom: remove unnecessary boot_lock
  ARM: 8832/1: NOMMU: Limit visibility for CONFIG_FLASH_{MEM_BASE,SIZE}
  ARM: 8831/1: NOMMU: pmsa-v8: remove unneeded semicolon
  ...
</content>
</entry>
<entry>
<title>Merge tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux</title>
<updated>2019-03-14T15:46:17+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-03-14T15:46:17+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=dc2535be1fd547fbd56aff091370280007b0a1af'/>
<id>urn:sha1:dc2535be1fd547fbd56aff091370280007b0a1af</id>
<content type='text'>
Pull clk subsystem updates from Stephen Boyd:
 "We have a fairly balanced mix of clk driver updates and clk framework
  updates this time around. It's the usual pile of new drivers for new
  hardware out there and the normal small fixes and updates, but then we
  have some core framework changes too.

  In the core framework, we introduce support for a clk_get_optional()
  API to get clks that may not always be populated and a way to devm
  manage clkdev lookups registered by provider drivers. We also do some
  refactoring to simplify the interface between clkdev and the common
  clk framework so we can reuse the DT parsing and clk_get() path in
  provider drivers in the future. This work will continue in the next
  few cycles while we convert how providers specify clk parents.

  On the driver side, the biggest part of the dirstat is the Amlogic clk
  driver that got support for the G12A SoC. It dominates with almost
  half the overall diff, while the second largest part of the diff is in
  the i.MX clk driver that gained support for imx8mm SoCs. After that,
  we have the Actions Semiconductor and Qualcomm drivers rounding out
  the big part of the dirstat because they both got new hardware support
  for SoCs. The rest is just various updates and non-critical fixes for
  existing drivers.

  Core:
   - Convert a few clk bindings to JSON schema format
   - Add a {devm_}clk_get_optional() API
   - Add devm_clk_hw_register_clkdev() API to manage clkdev lookups
   - Start rewriting clk parent registration and supporting device links
     by moving around code that supports clk_get() and DT parsing of the
     'clocks' property

  New Drivers:
   - Add Qualcomm MSM8998 RPM managed clks
   - IPA clk support on Qualcomm RPMh clk controllers
   - Actions Semi S500 SoC clk support
   - Support for fixed rate clks populated from an MMIO register
   - Add RPC (QSPI/HyperFLASH) clocks on Renesas R-Car V3H
   - Add TMU (timer) clocks on Renesas RZ/G2E
   - Add Amlogic G12A Always-On Clock Controller
   - Add 32k clock generation for Amlogic AXG
   - Add support for the Mali GPU clocks on Amlogic Meson8
   - Add Amlogic G12A EE clock controller driver
   - Add missing CANFD clocks on Renesas RZ/G2M and RZ/G2E
   - Add i.MX8MM SoC clk driver support

  Removed Drivers:
   - Remove clps711x driver as the board support is gone

  Updates:
   - 3rd ECO fix for Mediatek MT2712 SoCs
   - Updates for Qualcomm MSM8998 GCC clks
   - Random static analysis fixes for clk drivers
   - Support for sleeping gpios in the clk-gpio type
   - Minor fixes for STM32MP1 clk driver (parents, critical flag, etc.)
   - Split LCDC into two clks on the Marvell MMP2 SoC
   - Various DT of_node refcount fixes
   - Get rid of CLK_IS_BASIC from TI code (yay!)
   - TI Autoidle clk support
   - Fix Amlogic Meson8 APB clock ID name
   - Claim input clocks through DT for Amlogic AXG and GXBB
   - Correct the DU (display unit) parent clock on Renesas RZ/G2E
   - Exynos5433 IMEM CMU crypto clk support (SlimSS)
   - Fix for the PLL-MIPI on the Allwinner A23
   - Fix Rockchip rk3328 PLL rate calculation
   - Add SET_RATE_PARENT flag on display clk of Rockhip rk3066
   - i.MX SCU clk driver clk_set_parent() and cpufreq support"

* tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux: (150 commits)
  dt-bindings: clock: imx8mq: Fix numbering overlaps and gaps
  clk: ti: clkctrl: Fix clkdm_name regression for TI_CLK_CLKCTRL_COMPAT
  clk: fixup default index for of_clk_get_by_name()
  clk: Move of_clk_*() APIs into clk.c from clkdev.c
  clk: Inform the core about consumer devices
  clk: Introduce of_clk_get_hw_from_clkspec()
  clk: core: clarify the check for runtime PM
  clk: Combine __clk_get() and __clk_create_clk()
  clk: imx8mq: add GPIO clocks to clock tree
  clk: mediatek: correct cpu clock name for MT8173 SoC
  clk: imx: Refactor entire sccg pll clk
  clk: imx: scu: add cpu frequency scaling support
  clk: mediatek: Mark bus and DRAM related clocks as critical
  clk: mediatek: Add flags to mtk_gate
  clk: mediatek: Add MUX_FLAGS macro
  clk: qcom: gcc-sdm845: Define parent of PCIe PIPE clocks
  clk: ingenic: Remove set but not used variable 'enable'
  clk: at91: programmable: remove unneeded register read
  clk: mediatek: using CLK_MUX_ROUND_CLOSEST for the clock of dpi1_sel
  clk: mediatek: add MUX_GATE_FLAGS_2
  ...
</content>
</entry>
<entry>
<title>Merge branches 'clk-imx', 'clk-samsung', 'clk-ti', 'clk-uniphier-gear' and 'clk-mmp2-lcdc' into clk-next</title>
<updated>2019-03-08T18:27:40+00:00</updated>
<author>
<name>Stephen Boyd</name>
<email>sboyd@kernel.org</email>
</author>
<published>2019-03-08T18:27:40+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=e7faa095cbd761ec9e0c0dd83a7425b19ddce510'/>
<id>urn:sha1:e7faa095cbd761ec9e0c0dd83a7425b19ddce510</id>
<content type='text'>
 - Split LCDC into two clks on the Marvell MMP2 SoC

* clk-imx:
  clk: imx8mq: add GPIO clocks to clock tree
  clk: imx: Refactor entire sccg pll clk
  clk: imx: scu: add cpu frequency scaling support
  clk: imx: imx8mm: Mark init function __init
  clk: imx8mq: Add the missing ARM clock
  dt-bindings: imx8mq-clock: Add the missing ARM clock
  clk: imx: imx8mq: Fix the rate propagation for arm pll
  clk: imx8mq: Add support for the CLKO1 clock
  clk: imx8mq: Fix the CLKO2 source select list
  clk: imx8mq: Add missing M4 clocks
  clk: imx: Add clock driver support for imx8mm
  dt-bindings: imx: Add clock binding doc for imx8mm
  clk: imx: Add PLLs driver for imx8mm soc
  clk: imx5: add imx5_SCC2_IPG_GATE
  clk: imx: scu: add set parent support
  clk: imx: scu: add fallback compatible string support
  clk: imx8mq: Make parent names arrays const pointers
  clk: imx: Make parents const pointer in mux wrappers
  clk: imx: Make parent_names const pointer in composite-8m

* clk-samsung:
  clk: samsung: s3c2443: Mark expected switch fall-through
  clk: samsung: exynos5: Fix kfree() of const memory on setting driver_override
  clk: samsung: exynos5: Fix possible NULL pointer exception on platform_device_alloc() failure
  clk: samsung: exynos5433: Add selected IMEM clocks
  clk: samsung: dt-bindings: Document Exynos5433 IMEM CMU
  clk: samsung: exynos5433: Fix name typo in sssx
  clk: samsung: exynos5433: Fix definition of CLK_ACLK_IMEM_{200, 266} clocks
  clk: samsung: dt-bindings: Add Exynos5433 IMEM CMU clock IDs

* clk-ti:
  clk: clk-twl6040: Fix imprecise external abort for pdmclk
  ARM: OMAP2+: hwmod: disable ick autoidling when a hwmod requires that
  clk: ti: check clock type before doing autoidle ops
  clk: ti: add a usecount for autoidle
  clk: ti: generalize the init sequence of clk_hw_omap clocks
  clk: ti: remove usage of CLK_IS_BASIC
  clk: ti: add new API for checking if a provided clock is an OMAP clock
  clk: ti: move clk_hw_omap list handling under generic part of the driver

* clk-uniphier-gear:
  clk: uniphier: Fix update register for CPU-gear

* clk-mmp2-lcdc:
  clk: mmp2: separate LCDC peripheral clk form the display clock
  dt-bindings: marvell,mmp2: Add clock id for the LCDC clock
</content>
</entry>
<entry>
<title>Merge tag 'armsoc-dt' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc</title>
<updated>2019-03-06T17:36:37+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-03-06T17:36:37+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=6ad63dec9c2c80710896edd1996e56c54a230870'/>
<id>urn:sha1:6ad63dec9c2c80710896edd1996e56c54a230870</id>
<content type='text'>
Pull ARM SoC device tree updates from Arnd Bergmann:
 "This is a smaller update than the past few times, but with just over
  500 non-merge changesets still dwarfes the rest of the SoC tree.

  Three new SoC platforms get added, each one a follow-up to an existing
  product, and added here in combination with a reference platform:

   - Renesas RZ/A2M (R7S9210) 32-bit Cortex-A9 Real-time imaging
     processor:

       https://www.renesas.com/eu/en/products/microcontrollers-microprocessors/rz/rza/rza2m.html

   - Renesas RZ/G2E (r8a774c0) 64-bit Cortex-A53 SoC "for Rich Graphics
     Applications":

       https://www.renesas.com/eu/en/products/microcontrollers-microprocessors/rz/rzg/rzg2e.html

   - NXP i.MX8QuadXPlus 64-bit Cortex-A35 SoC:

       https://www.nxp.com/products/processors-and-microcontrollers/arm-based-processors-and-mcus/i.mx-applications-processors/i.mx-8-processors/i.mx-8x-family-arm-cortex-a35-3d-graphics-4k-video-dsp-error-correcting-code-on-ddr:i.MX8X

  These are actual commercial products we now support with an in-kernel
  device tree source file:

   - Bosch Guardian is a product made by Bosch Power Tools GmbH, based
     on the Texas Instruments AM335x chip

   - Winterland IceBoard is a Texas Instruments AM3874 based machine
     used in telescopes at the south pole and elsewhere, see commit
     d031773169df2 for some pointers:

   - Inspur on5263m5 is an x86 server platform with an Aspeed ast2500
     baseboard management controller. This is for running on the BMC.

   - Zodiac Digital Tapping Unit, apparently a kind of ethernet switch
     used in airplanes.

   - Phicomm K3 is a WiFi router based on Broadcom bcm47094

   - Methode Electronics uDPU FTTdp distribution point unit

   - X96 Max, a generic TV box based on Amlogic G12a (S905X2)

   - NVIDIA Shield TV (Darcy) based on Tegra210

  And then there are several new SBC, evaluation, development or modular
  systems that we add:

   - Three new Rockchips rk3399 based boards:
       - FriendlyElec NanoPC-T4 and NanoPi M4
       - Radxa ROCK Pi 4

   - Five new i.MX6 family SoM modules and boards for industrial
     products:
       - Logic PD i.MX6QD SoM and evaluation baseboad
       - Y Soft IOTA Draco/Hydra/Ursa family boards based on i.MX6DL
       - Phytec phyCORE i.MX6 UltraLite SoM and evaluation module

   - MYIR Tech MYD-LPC4357 development based on the NXP lpc4357
     microcontroller

   - Chameleon96, an Intel/Altera Cyclone5 based FPGA development system
     in 96boards form factor

   - Arm Fixed Virtual Platforms(FVP) Base RevC, a purely virtual
     platform for corresponding to the latest "fast model"

   - Another Raspberry Pi variant: Model 3 A+, supported both in 32-bit
     and 64-bit mode.

   - Oxalis Evalkit V100 based on NXP Layerscape LS1012a, in 96Boards
     enterprise form factor

   - Elgin RV1108 R1 development board based on 32-bit Rockchips RV1108

  For already supported boards and SoCs, we often add support for new
  devices after merging the drivers. This time, the largest changes
  include updates for

   - STMicroelectronics stm32mp1, which was now formally launched last
     week

   - Qualcomm Snapdragon 845, a high-end phone and low-end laptop chip

   - Action Semi S700

   - TI AM654x, their recently merged 64-bit SoC from the OMAP family

   - Various Amlogic Meson SoCs

   - Mediatek MT2712

   - NVIDIA Tegra186 and Tegra210

   - The ancient NXP lpc32xx family

   - Samsung s5pv210, used in some older mobile phones

  Many other chips see smaller updates and bugfixes beyond that"

* tag 'armsoc-dt' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (506 commits)
  ARM: dts: exynos: Fix max voltage for buck8 regulator on Odroid XU3/XU4
  dt-bindings: net: ti: deprecate cpsw-phy-sel bindings
  ARM: dts: am335x: switch to use phy-gmii-sel
  ARM: dts: am4372: switch to use phy-gmii-sel
  ARM: dts: dm814x: switch to use phy-gmii-sel
  ARM: dts: dra7: switch to use phy-gmii-sel
  arch: arm: dts: kirkwood-rd88f6281: Remove disabled marvell,dsa reference
  ARM: dts: exynos: Add support for secondary DAI to Odroid XU4
  ARM: dts: exynos: Add support for secondary DAI to Odroid XU3
  ARM: dts: exynos: Disable ARM PMU on Odroid XU3-lite
  ARM: dts: exynos: Add stdout path property to Arndale board
  ARM: dts: exynos: Add minimal clkout parameters to Exynos3250 PMU
  ARM: dts: exynos: Enable ADC on Odroid HC1
  arm64: dts: sprd: Remove wildcard compatible string
  arm64: dts: sprd: Add SC27XX fuel gauge device
  arm64: dts: sprd: Add SC2731 charger device
  arm64: dts: sprd: Add ADC calibration support
  arm64: dts: sprd: Remove PMIC INTC irq trigger type
  arm64: dts: rockchip: Enable tsadc device on rock960
  ARM: dts: rockchip: add chosen node on veyron devices
  ...
</content>
</entry>
<entry>
<title>Merge branch 'regulator-5.1' into regulator-next</title>
<updated>2019-03-04T15:32:43+00:00</updated>
<author>
<name>Mark Brown</name>
<email>broonie@kernel.org</email>
</author>
<published>2019-03-04T15:32:43+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=88f268a5bcc3b0683e6fbaf9973702e5329fc1e3'/>
<id>urn:sha1:88f268a5bcc3b0683e6fbaf9973702e5329fc1e3</id>
<content type='text'>
</content>
</entry>
<entry>
<title>ARM: OMAP2+: hwmod: disable ick autoidling when a hwmod requires that</title>
<updated>2019-02-15T14:48:11+00:00</updated>
<author>
<name>Andreas Kemnade</name>
<email>andreas@kemnade.info</email>
</author>
<published>2019-01-16T22:04:29+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=12af39cad78e9cb8172793ca5d7f369eb144578b'/>
<id>urn:sha1:12af39cad78e9cb8172793ca5d7f369eb144578b</id>
<content type='text'>
Deny autoidle for hwmods with the OCPIF_SWSUP_IDLE flag,
that makes hwmods working properly which cannot handle
autoidle properly in lower power states.
Affected is e. g. the omap_hdq.
Since an ick might have mulitple users, autoidle is disabled
when an individual user requires that rather than in
_setup_iclk_autoidle. dss_ick is an example for that.

Signed-off-by: Andreas Kemnade &lt;andreas@kemnade.info&gt;
Acked-by: Tony Lindgren &lt;tony@atomide.com&gt;
Tested-by: Keerthy &lt;j-keerthy@ti.com&gt;
Signed-off-by: Tero Kristo &lt;t-kristo@ti.com&gt;
</content>
</entry>
<entry>
<title>ARM: OMAP2+: fix lack of timer interrupts on CPU1 after hotplug</title>
<updated>2019-02-07T15:48:22+00:00</updated>
<author>
<name>Russell King</name>
<email>rmk+kernel@armlinux.org.uk</email>
</author>
<published>2018-12-12T11:49:47+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=50d6b3cf9403879911e06d69c7ef41e43f8f7b4b'/>
<id>urn:sha1:50d6b3cf9403879911e06d69c7ef41e43f8f7b4b</id>
<content type='text'>
If we have a kernel configured for periodic timer interrupts, and we
have cpuidle enabled, then we end up with CPU1 losing timer interupts
after a hotplug.

This can manifest itself in RCU stall warnings, or userspace becoming
unresponsive.

The problem is that the kernel initially wants to use the TWD timer
for interrupts, but the TWD loses context when we enter the C3 cpuidle
state.  Nothing reprograms the TWD after idle.

We have solved this in the past by switching to broadcast timer ticks,
and cpuidle44xx switches to that mode at boot time.  However, there is
nothing to switch from periodic mode local timers after a hotplug
operation.

We call tick_broadcast_enter() in omap_enter_idle_coupled(), which one
would expect would take care of the issue, but internally this only
deals with one-shot local timers - tick_broadcast_enable() on the other
hand only deals with periodic local timers.  So, we need to call both.

Signed-off-by: Russell King &lt;rmk+kernel@armlinux.org.uk&gt;
[tony@atomide.com: just standardized the subject line]
Signed-off-by: Tony Lindgren &lt;tony@atomide.com&gt;
</content>
</entry>
<entry>
<title>regulator: fixed/gpio: Pull inversion/OD into gpiolib</title>
<updated>2019-02-06T15:58:29+00:00</updated>
<author>
<name>Linus Walleij</name>
<email>linus.walleij@linaro.org</email>
</author>
<published>2019-01-29T10:31:53+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=01dc79cd6fe7d25b0eba84009634f5435cbdb4e6'/>
<id>urn:sha1:01dc79cd6fe7d25b0eba84009634f5435cbdb4e6</id>
<content type='text'>
This pushes the handling of inversion semantics and open drain
settings to the GPIO descriptor and gpiolib. All affected board
files are also augmented.

This is especially nice since we don't have to have any
confusing flags passed around to the left and right littering
the fixed and GPIO regulator drivers and the regulator core.
It is all just very straight-forward: the core asks the GPIO
line to be asserted or deasserted and gpiolib deals with the
rest depending on how the platform is configured: if the line
is active low, it deals with that, if the line is open drain,
it deals with that too.

Cc: Alexander Shiyan &lt;shc_work@mail.ru&gt; # i.MX boards user
Cc: Haojian Zhuang &lt;haojian.zhuang@gmail.com&gt; # MMP2 maintainer
Cc: Aaro Koskinen &lt;aaro.koskinen@iki.fi&gt; # OMAP1 maintainer
Cc: Tony Lindgren &lt;tony@atomide.com&gt; # OMAP1,2,3 maintainer
Cc: Mike Rapoport &lt;rppt@linux.vnet.ibm.com&gt; # EM-X270 maintainer
Cc: Robert Jarzmik &lt;robert.jarzmik@free.fr&gt; # EZX maintainer
Cc: Philipp Zabel &lt;philipp.zabel@gmail.com&gt; # Magician maintainer
Cc: Petr Cvek &lt;petr.cvek@tul.cz&gt; # Magician
Cc: Robert Jarzmik &lt;robert.jarzmik@free.fr&gt; # PXA
Cc: Paul Parsons &lt;lost.distance@yahoo.com&gt; # hx4700
Cc: Daniel Mack &lt;zonque@gmail.com&gt; # Raumfeld maintainer
Cc: Marc Zyngier &lt;marc.zyngier@arm.com&gt; # Zeus maintainer
Cc: Geert Uytterhoeven &lt;geert+renesas@glider.be&gt; # SuperH pinctrl/GPIO maintainer
Cc: Russell King &lt;rmk+kernel@armlinux.org.uk&gt; # SA1100
Tested-by: Marek Szyprowski &lt;m.szyprowski@samsung.com&gt;
Tested-by: Janusz Krzysztofik &lt;jmkrzyszt@gmail.com&gt; #OMAP1 Amstrad Delta
Signed-off-by: Linus Walleij &lt;linus.walleij@linaro.org&gt;
Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
</content>
</entry>
<entry>
<title>ARM: avoid Cortex-A9 livelock on tight dmb loops</title>
<updated>2019-02-01T22:05:50+00:00</updated>
<author>
<name>Russell King</name>
<email>rmk+kernel@armlinux.org.uk</email>
</author>
<published>2018-04-10T10:35:36+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=5388a5b82199facacd3d7ac0d05aca6e8f902fed'/>
<id>urn:sha1:5388a5b82199facacd3d7ac0d05aca6e8f902fed</id>
<content type='text'>
machine_crash_nonpanic_core() does this:

	while (1)
		cpu_relax();

because the kernel has crashed, and we have no known safe way to deal
with the CPU.  So, we place the CPU into an infinite loop which we
expect it to never exit - at least not until the system as a whole is
reset by some method.

In the absence of erratum 754327, this code assembles to:

	b	.

In other words, an infinite loop.  When erratum 754327 is enabled,
this becomes:

1:	dmb
	b	1b

It has been observed that on some systems (eg, OMAP4) where, if a
crash is triggered, the system tries to kexec into the panic kernel,
but fails after taking the secondary CPU down - placing it into one
of these loops.  This causes the system to livelock, and the most
noticable effect is the system stops after issuing:

	Loading crashdump kernel...

to the system console.

The tested as working solution I came up with was to add wfe() to
these infinite loops thusly:

	while (1) {
		cpu_relax();
		wfe();
	}

which, without 754327 builds to:

1:	wfe
	b	1b

or with 754327 is enabled:

1:	dmb
	wfe
	b	1b

Adding "wfe" does two things depending on the environment we're running
under:
- where we're running on bare metal, and the processor implements
  "wfe", it stops us spinning endlessly in a loop where we're never
  going to do any useful work.
- if we're running in a VM, it allows the CPU to be given back to the
  hypervisor and rescheduled for other purposes (maybe a different VM)
  rather than wasting CPU cycles inside a crashed VM.

However, in light of erratum 794072, Will Deacon wanted to see 10 nops
as well - which is reasonable to cover the case where we have erratum
754327 enabled _and_ we have a processor that doesn't implement the
wfe hint.

So, we now end up with:

1:      wfe
        b       1b

when erratum 754327 is disabled, or:

1:      dmb
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        wfe
        b       1b

when erratum 754327 is enabled.  We also get the dmb + 10 nop
sequence elsewhere in the kernel, in terminating loops.

This is reasonable - it means we get the workaround for erratum
794072 when erratum 754327 is enabled, but still relinquish the dead
processor - either by placing it in a lower power mode when wfe is
implemented as such or by returning it to the hypervisior, or in the
case where wfe is a no-op, we use the workaround specified in erratum
794072 to avoid the problem.

These as two entirely orthogonal problems - the 10 nops addresses
erratum 794072, and the wfe is an optimisation that makes the system
more efficient when crashed either in terms of power consumption or
by allowing the host/other VMs to make use of the CPU.

I don't see any reason not to use kexec() inside a VM - it has the
potential to provide automated recovery from a failure of the VMs
kernel with the opportunity for saving a crashdump of the failure.
A panic() with a reboot timeout won't do that, and reading the
libvirt documentation, setting on_reboot to "preserve" won't either
(the documentation states "The preserve action for an on_reboot event
is treated as a destroy".)  Surely it has to be a good thing to
avoiding having CPUs spinning inside a VM that is doing no useful
work.

Acked-by: Will Deacon &lt;will.deacon@arm.com&gt;
Signed-off-by: Russell King &lt;rmk+kernel@armlinux.org.uk&gt;
</content>
</entry>
</feed>
