Linux 4.7 Release – Main Changes, ARM and MIPS Architectures

Linux 4.7 is out:

So, after a slight delay due to my travels, I’m back, and 4.7 is out.

Despite it being two weeks since rc7, the final patch wasn’t all that big, and much of it is trivial one- and few-liners. There’s a couple of network drivers that got a bit more loving. Appended is the shortlog since rc7 for people who care: it’s fairly spread out, with networking and some intel Kabylake GPU fixes being the most noticeable ones. But there’s random small noise spread all over.

And obviously, this means that the merge window for 4.8 is open.Judging by the linux-next contents, that’s going to be a bigger release than the current one (4.7 really was fairly calm, I blame at least partly summer in the northern hemisphere).

Linus

Linux 4.6 brought USB 3.1 superspeed, OrangeFS distributed file system, 802.1AE MAC-level encryption (MACsec), and BATMAN V protocol support, improved the reliability of OOM task killer, and more.

Linux 4.7 most noticeable changes include:

Support for Radeon RX480 GPUs
Parallel directory lookups – The directory cache caches information about path names to make them quickly available for pathname lookup. This cache uses a mutex to serialize lookup of names in the same directory. The serializing mutex has been switched to a read-write semaphore in Linux 4.7, allowing for parallel pathname lookups in the same directory. Most filesystems have been converted to allow this feature.
New “schedutil” frequency governor – There are two main differences between it and the existing governors. First, it uses information provided by the scheduler directly for making its decisions. Second, it can invoke cpufreq drivers and change the frequency to adjust CPU performance right away, without having to spawn work items to be executed in process context or similar, leading to lower latency to make frequency changes.

Histograms of events in ftrace – . This release adds the “hist” command, which provides the ability to build “histograms” of events by aggregating event hits. As an example, let’s say a user needs to get a list of bytes read from files from each process. You can get this information using hist triggers, with the following command command:

echo 'hist:key=common_pid.execname:val=count:sort=count.descending' > /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger

1	echo 'hist:key=common_pid.execname:val=count:sort=count.descending' > /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger

other data can also be retrieve by using fields found in /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/format. The output will look like:

# cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/hist 
 trigger info: hist:keys=common_pid.execname:vals=count:sort=count.descending:size=2048 [active]

{ common_pid: gnome-terminal  [      3196] } hitcount:        280  count:    1093512
{ common_pid: Xorg            [      1309] } hitcount:        525  count:     256640
{ common_pid: compiz          [      2889] } hitcount:         59  count:     254400
{ common_pid: bash            [      8710] } hitcount:          3  count:      66369
...
{ common_pid: gdbus           [      2998] } hitcount:          1  count:         16
{ common_pid: rtkit-daemon    [      2052] } hitcount:          1  count:          8
{ common_pid: init            [         1] } hitcount:          2  count:          2

    Totals:
        Hits: 2116
        Entries: 51
        Dropped: 0

# cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/hist

trigger info: hist:keys=common_pid.execname:vals=count:sort=count.descending:size=2048 [active]

{ common_pid: gnome-terminal [ 3196] } hitcount: 280 count: 1093512

{ common_pid: Xorg [ 1309] } hitcount: 525 count: 256640

{ common_pid: compiz [ 2889] } hitcount: 59 count: 254400

{ common_pid: bash [ 8710] } hitcount: 3 count: 66369

...

{ common_pid: gdbus [ 2998] } hitcount: 1 count: 16

{ common_pid: rtkit-daemon [ 2052] } hitcount: 1 count: 8

{ common_pid: init [ 1] } hitcount: 2 count: 2

Totals:

Entries: 51

Dropped: 0

More more details check ftrace documentation and related LWN article.

EFI ‘Capsule’ firmware updates – The EFI Capsule mechanism allows to pass data blobs to the EFI firmware. The firmware then parses them and makes some decision based upon their contents. The most common use case is to bundle a flashable firmware image into a capsule that the firmware can use to upgrade in the next boot the existing version in the flash. Users can upload capsule by writing the firmware to the /dev/efi_capsule_loader device
Support for creating virtual USB Device Controllers in USB/IP – USB/IP allows to share real USB devices over the network. Linux 4.7 brings the ability to create virtual USB Device Controllers without needing any physical USB device, using the USB gadget subsystem. For what purpose? For example, for improving phone emulation in development environments, for testing USB and for educational purposes.

Some of ARM specific improvements and new features include:

Allwinner:
- Allwinner A13/R8 – Display Engine support
- Allwinner A10/A20 – S/PDIF Support
- Allwinner A31/A23/H3 – DMAengine improvements for H3 audio support
- Allwinner H3 – USB support (multi-reset line support delayed til 4.8)
- New hardware supported
  - Tablets – Dserve DSRV9703C, Polaroid MID2809PXE4, Colorfly e708 q1, Difrence DIT4350
  - Boards – Olimex A20 OLinuXino LIME2, Xunlong Orange Pi 2, Orange Pi One, and Orange Pi PC

Rockchip:
- Thermal management – Rockchip driver support for RK3399, RK3366
- Added Rockchip RK3399 clock and reset controller
- Pinctrl – Support the .get_direction() callback in the GPIO portions
- New RK3399 device tree support
- Added Rockchip DisplayPort PHY support
- Added Geekbuying GeekBox, RK3399 Evaluation Board, mqmaker MiQi SBC
Amlogic
- Added Meson GXBB (S905) pinctrl support
- Fixed memory nodes on Vega S95 DTS
- Added Hardkernel ODROID-C2, Amlogic Meson GXBB P200 and P201 development systems
Samsung
- Added Samsung ARTIK5 evaluation board
- Added generic exynos bus frequency driver
- Added pinctrl driver for Samsung EXYNOS5440 SoC
- DTS updates & fixes:
  - Fix s5p-mfc driver probe on Exynos542x Peach boards (need to provide MFC memory banks). On these boards this was broken for long time but apparently no one enabled this driver till now.
  - Fix creation of debugfs entries for one regulator on Exynos4210 Trats board.
  - Fix probing of max8997 MFD driver (and its children) because of missing interrupt. Actually the current version of the driver probes (just without interrupts) but after switching to regmap and regmap-irq, the interrupt will be mandatory.
  - Cleanup regulator bindings on Exynos5420 boards.
  - Support MIC bypass in display path for Exynos5420.
  - Enable PRNG and SSS for all Exynos4 devices.
  - Add PL330 DMA controller and Thermal Management Unit to Exynos 7
  - Enable accelerated AES (Security SubSystem) on Exynos4412-based boards
  - Enable HDMI CEC on Exynos4412-based Odroid.
  - Add regulator supplies for eMMC/SD on Odroid XU3/XU4.
  - Fix DTC unit name warnings.
Qualcomm
- Qualcomm IPQ4019 support in pinctrl
- Change SMD callback parameters
- 96Boards HiKey based on the Hisilicon Hi6220 (Kirin 620) gets an overhaul with a lot of devices enabled in the DT.
- Added Qualcomm IPQ4019 “Internet processor”, Arrow DragonBoard 600c (96boards) with APQ8064 Snapdragon 600
- Device tree changes:
  - Add additional nodes for APQ8064
  - Fix APQ8064 pinctrls for i2c/spi
  - Add MSM8974 nodes for smp2p and smd
  - Modify MSM8974 memory reserve for rfsa and rmtfs
  - Add support for BQ27541 on Nexus7
Mediatek
- Added CPU power cooling model to Mediatek thermal driver
- Added Mediatek MT8173 display driver, DRM driver, and thermal controller
- Added MIPI DSI sub driver
- 4GB mode support for Mediatek IOMMU driver
- DTS updates:
  - add pinctrl node for mt2701
  - add mt2701 pmic wrapper binding
  - add auxadc binding document
Other new ARM hardware or SoCs – LG1312 TV SoC, Hisilicon Hip06/D03, Google Pixel C, NXP Layerscape 1043A QDS development board, Aspeed AST2400/AST2500, Oxnas 810SE (WD My Book World Edition), ARM MPS2 (AN385 Cortex-M3 & AN399 Cortex-M7), Ka-Ro electronics industrial SoM modules, Embest MarS Board, Boundary Devices i.MX6 Quad Plus Nitrogen6_MAX and SoloX Nitrogen6sx embedded boards, Technexion Pico i.MX6UL compute module, ZII VF610 Development Board, Linksys Viper (E4200v2 / EA4500) WiFi router, Buffalo Kurobox Pro NAS, samtec VIN|ING 1000 vehicle communication interface, Amazon Kindle Fire first generation tablet and ebook reader, OnRISC Baltos iR 2110 and 3220 embedded industrial PCs, TI AM5728 IDK, TI AM3359 ICE-V2, and TI DRA722 Rev C EVM development systems.

MIPS architecture changelog:

Add support for relocatable kernel so it can be loaded someplace besides the default 1MB.
Add KASLR support using relocatable support
Add perf counter feature
Add support for extending builtin cmdline
seccomp: Support compat with both O32 and N32
ath79: Add support for DTB passed using the UHI boot protocol, remove the builtin DTB support, add zboot debug serial support, add initial support for DPT-Module, Dragino MS14 (Dragino 2), and Onion Omega
BMIPS: Add BCM6358 support, add Whirlwind (BMIPS5200) initialization code, add support for BCM63268
Lantiq: Add support for device tree file from boot loader
Add basic Loongson 3A support
Add support for CN73xx, CN75xx and CN78xx
Octeon: Add DTS for D-Link DSR-1000N
Detect DSP v3 support
Detect MIPSr6 Virtual Processor support
Enable ptrace hw watchpoints on MIPS R6
Probe the M6250 CPUand the P6600 core
Support sending SIG_SYS to 32bit userspace from 64bit kernel
qca: introduce AR9331 devicetree
ralink: add MT7628 EPHY LEDs pinmux support
smp-cps: Add nothreads kernel parameter
smp-cps: Support MIPSr6 Virtual Processors
MIPS64: Support a maximum at least 48 bits of application virtual

For even much more details, you can check out Linux 4.7 changelog with comments only generated using git log v4.6..v4.7 --stat. Alternatively, and much easier to read, you can head to kernelnewbies.org to learn more about Linux 4.7 changes.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.