Linux 5.5 Release - Main Changes, Arm, MIPS and RISC-V Architectures

Linux 5.5 has just been released by Linus Torvalds:

So this last week was pretty quiet, and while we had a late network update with some (mainly iwl wireless) network driver and netfilter module loading fixes, David didn’t think that warranted another -rc. And outside of that, it’s really been very quiet indeed – there’s a panfrost driver update too, but again it didn’t really seem to make sense to delay the final release by another week.

Outside of those, it’s all really tiny, even if some of those tiny changes touched some core files.

So despite the slight worry that the holidays might have affected the schedule, 5.5 ended up with the regular rc cadence and is out now.

That means that the merge window for 5.6 will open tomorrow, and I already have a couple of pull requests pending. The timing for this next merge window isn’t optimal for me – I have some travel and other things going on during the same two weeks, but hopefully it won’t be all that noticeable. But there might be random timezones, odd hours, and random delays because of that. I try to avoid scheduling things during the merge window, but hey, it doesn’t always work out, and I’d have to delay things by two weeks to avoid the conflicts, which just doesn’t seem worth it.

Particularly since it’s not necessarily going to be a problem to begin
with. We’ll see.

Anyway. Go out and test 5.5, and start sending me those pull requests for all the new development that is ready,

Linus

Linux 5.4 brought us supports for new AMD GPUs and Intel graphics found in Tiger Lake processor, kernel lockdown mode, virtio-fs file system for virtualized guests, and fs-verity file systems authenticity protection, among many other changes.

Some notable changes for Linux 5.5:

io_uring asynchronous I/O improvements – Ability to modify the set of files being operated on without starting over, user-specifiable completion-ring sizes, absolute timeouts, and support for accept() calls among others.
Airtime Queue Limits (AQL) for WiFi make CoDel work effectively with wireless drivers that utilized firmware/hardware offloading.
KUnit unit testing framework for the Linux kernel with tests that can be run locally on a developer’s workstation without a VM or special hardware.
SMB rootfs and multichannel support – SMB supports using SMB as root file systems, and support for using multiple network connections for the same SMB session.

Some of the changes related to Arm architecture include:

Allwinner
- Allwinner H3 – Deinterlace driver
- Allwinner H6 – Crypto, Mali 3D GPU, USB3 PHY (for boards not needing vbus switching)
- Allwinner A64 / A80 / A83T / H3 / H5 / R40 – Crypto
- Multiple SoCs – Cedrus HEVC/H.265 decoding
- Broadcom-based (AMPAK modules) Bluetooth support on Emlid Neutis
- New Devices Supported – FriendlyELEC NanoPi Duo2
Rockchip
- Added RK3308 SoC
- Clk drivers – Improve Rockchip px30 clk tree
- Host bridge driver – Make rockchip 0V9 and 1V8 power regulators non-optional
- New boards and products – Beelink A1 (rk3328), rk3308 eval boards, rk3399-roc-pc
Amlogic
- Added support for Meson A1 dual-core Cortex-A35 and G12 processors
- New Amlogic soc thermal driver
- Arm64 DTS updates
  - g12: add thermal driver and cooling properties
  - sm1: enable audio on SEI610 board
  - IR: add several keymaps
  - sdio: add keep-power-in-suspend property for multiple boards
  - pcie: add support for G12A
  - multiple fixes, cleanups
- New boards – Ugoos AM6 TV box, Amlogic AD401 (A1 based)
Samsung
- Updated Samsung Exynos 5422 driver for DMC (dynamic memory configuration), and ASV (adaptive voltage) allowing the platform to run at more optimal operating points.
- clk driver updates – Addition of rate table for the VPLL and GPU related clock tree definition update to allow the GPU driver for setting
  the GPU’s clock without requiring detailed knowledge of
  clock topology on each exynos542x SoC; fix for potential CPU performance degradation after system suspend/resume cycle on exynos542x SoCs
- defconfig changes
  - Enable Dynamic Memory Controller driver for Exynos5422,
  - Enable Arndale (Exynos5250) audio driver,
  - Sync multi_v7 defconfig with exynos by enabling useful and necessary
    drivers (NFC, watchdog, S2MPA01 regulator, IOMMU, Maxim extcon
    drivers, PHY for SATA and devfreq).
- DTS ARM64 changes for Linux 5.5
  - Fix boot of Exynos7 due to wrong address/size of memory node,
  - Move GPU under /soc node,
  - Minor of DT bindings
- DTS ARM changes for Linux 5.5
  - Add ARM architected timers on Exynos5 for KVM-based virtualization,
  - Extend chip identification needed for future Adaptive Supply Voltage,
  - Add audio support to Arndale board,
  - Fix init order of clock providers on s3c64xx,
  - A lot of cleanups and adjustments of DTS with DT schema.
Qualcomm
- IRQ Subsystem – Qualcomm PDC wakeup interrupt support
- iommu – Support for the Qualcomm SMMUv2 implementation in the SDM845 SoC
- Clk drivers – New: Qualcomm MSM8998 GPU clk controllers, Qualcomm SC7180 GCC and RPMH clk controllers, Qualcomm QCS404 Q6SSTOP clk controllers
- Pinctrl – Added support for Qualcomm MSM8976 and MSM8956
- ARM64 updates:
  - Add thermal IRQ support on MSM8916, SDM845, MSM8996, and QCS404
  - Fix thermal HW ids for cpus on MSM8916
  - Add blsp1 UART3 and blsp1 BAM on MSM8998
  - Add volume buttons and WCNSS for Wifi and BT on MSM8916 LongCheer-l8150
  - Fixup load on l21 for SD on apq8096-db820c
  - Enable LVS1/2, APSS watchdog, and select UFS reset gpio for SDM845
  - Disable coresight by default on MSM8998
  - Enable bluetooth and remove retention idle state on MSM8998-clamshell
  - Enable adsp, cdsp, and mpss on C630
  - Enable bluetooth on MSM8998-mtp
  - Delete zap shader on SDM845-cheza
  - Add tactile buttons and hall sensor on MSM8916-Samsung-A2015
  - Add Interconnect nodes, watchdog, and sleep clk on QCS404
  - Override Iris compatible on MSM8916-Samsung-A5U
  - Enable WCNSS Wifi and bluetooth on MSM8916-Samsung-A2015
  - Fixup cooling states for the aoss warming devices
- Device Tree Changes for Linux 5.5
  - Add thermal zones and IRQ support for MSM8974
  - Add 5vs2 regulator node for PM8941
  - Add reboot-mode node, fix sdhci and card detect on MSM8974-FP2
  - Add IPQ4019 SDHCI node
MediaTek – DRM next – mipi_tx, dsi, and partial crtc for MT8183 SoC.
Other new Arm hardware platforms and SoCs:
- Broadcom – BCM2711 (Raspberry Pi 4) processor
- Marvell – Armada AP807/AP807-quad and CP115 SoC, new EspressoBINn flavor
- Microchip/Atmel – Overkiz Kizbox2/4 (AT91) board
- NXP/Freescale
  - S32V234 32-bit Arm Cortex-A53 vision processor;
  - Boards – i.MX8MN LPDDR4 EVK, i.MX8QXP Colibri, S32V234 EVB, Netronix E60K02 and Kobo Clara HD, Kontron N6311 and N6411, OPOS6UL and OPOS6ULDev
- Realtek – RTD1293 and RTD1296 SoCs
- Renesas – Salvator-XS board

Linux 5.5 changelog for MIPS architecture:

Generic
- Atomics-related code sees some rework & cleanup, most notably
  allowing Loongson LL/SC errata workarounds to be more bulletproof &
  their correctness to be checked at build time.
- Command line setup code is simplified somewhat, resolving various
  corner cases.
- MIPS kernels can now be built with kcov code coverage support.
- We can now build with CONFIG_FORTIFY_SOURCE=y.
- Miscellaneous cleanups.
Platform-specific changes:
- Ingenic – Broken TLB functionality disabled on certain Ingenic
  systems, and JZ4780 systems gain some device tree nodes to support
  more devices.
- Loongson support sees a number of cleanups, plus initial support for Loongson 3A R4 systems.
- Mediatek – Support for MediaTek MT7688-based GARDENA Smart Gateway systems.
- SGI IP27 (Origin 2*) sees a number of fixes, cleanups & simplifications.
- SGI IP30 (Octane) systems are now supported”

Summary of changes for RISC-V architecture:

New features:
- SECCOMP support
- nommu support
- SBI-less system support
- M-Mode support
- TLB flush optimizations
- Dump some kernel virtual memory map details to the console if CONFIG_DEBUG_VM is enabled
Other improvements:
- Pass the complete RISC-V ISA string supported by the CPU cores to
  userspace, rather than redacting parts of it in the kernel
- Add platform DMA IP block data to the HiFive Unleashed board DT
  file
- Add Makefile support for BZ2, LZ4, LZMA, LZO kernel image
  compression formats, in line with other architectures
- Enable more debugging options in the primary defconfigs
Various code cleanups

For even more details, you can find the complete changelog with comments only generated using git log v5.4..v5.5-rc7 --stat command. Alternatively, you could also read Linux 5.5 changelog on KernelNewbies website.

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.