Linux 5.4 Release - Main Changes, Arm, MIPS & RISC-V Architectures

Linus Torvalds has just announced the release of Linux 5.4:

Not a lot happened this last week, which is just how I like it. And as expected, most of the pull requests I got were for the 5.5 merge window, which I’ll obviously start working through tomorrow.

What little there is here is mostly some networking updates (mix of network drivers and core networking), and some minor GPU driver updates. Other than that it’s a small collection of random other things all over. The appended shortlog is small enough that you might as well just scroll through it.

Anyway, this obviously opens the merge window for 5.5. It’s not ideal timing with Thanksgiving week coming up, but it hopefully shouldn’t be too much of an issue. If I fall behind (not because I’m all that big
of a fan of the indiscriminate and relentless turkey-killing holiday) it’s because we’ve got all three kids back for the holiday, and I might push some ot the merging to the second week as a result. We’ll see what happens.

Go do the testing thing.

Linus

Linux 5.3 added support for AMD Navi GPUs & Zhaoxin x86 CPUs, implemented Intel Speed Select power management technology, enabled 16 million new IPv4 addresses, and added IoT ACRN supervisor optimized for resource-constrained embedded systems, among many other improvements and new features.

Some interesting new features of Linux 5.4 include:

Support for new AMD/Intel graphics – amdgpu driver support four new products: Navi 12/14, Arcturus and Renoir APU support, while Linux 5.4 also adds initial support for Intel Tiger Lake GPU.
Kernel lockdown mode – Optional feature intended to strengthen the boundary between UID 0 (root) and the kernel. When enabled, various pieces of kernel functionality are restricted. Configuration can be done at runtime through securityfs, boot time via a kernel parameter, or build time via a KConfig option. You may want to read that LWN article for more details.
virtio-fs file system for virtualized guests – virtio-fs is a FUSE-based virtio driver for guest <-> host file system sharing. It takes advantage of the proximity of VMs to achieve API semantics and performance more like local file systems, and is an improvement over existing solutions such as NFS or virtio-9P. See documentation.
fs-verity detects file modifications in EXT-4 / F2FS (for now) – Support layer added to Linux 5.4 that filesystems can use to support transparent integrity and authenticity protection of read-only files. Read the documentation to find out how to use it.

A more detailed, albeit not exhaustive, list of changes for Arm architecture in Linux 5.4:

Allwinner
- Allwinner A20 – CSI camera interface
- Allwinner A64 – IR
- Allwinner H6 – IR, RTC, and S/PDIF
- New Devices & Boards – Olimex A64-OLinuXino eMMC board, Tanix TX6 TV box, Lichee Zero Plus (upcoming S3 board)
Rockchip
- Added clock driver for Rockchip rk3308 SoC
- Media – RK3399 VP8 decoding; Rockchip VPU JPEG encoder
- New boards – Mecer Xtreme Mini S6 is an Android “mini PC” box (RK3229); AOpen Chromebox Mini (Fievel) and Chromebase Mini (Tiger) running ChromeOS; Leez RK3399 P710 SBC
Amlogic
- Support for Amlogic SM1 (S905X3) and G12B (S922X, A311D)
- RTC – Amlogic Virtual Wake driver
- DTS
  - odroid-c1: use MAC address from efuse
  - add VDD_EE regulator to several boards
- New boards – Khadas VIM3/VIM3L, SEI Robotics SEI610 (S905X3)
Samsung
- Mach/SoC changes:
  - Minor fixup in plat and mach code (S3C platforms),
  - Add Exynos Chipid driver for identification of product IDs and SoC
    revisions
  - Extend the patterns for Samsung maintainer entries to cover all important files.
- DTS Arm changes:
  - Add AHCI to Exynos5250
  - Add camera and GPU power domains to Exynos5422
  - Fix Exynos542x Chromebooks boot with multi_v7 defconfig
  - Add GPU (Mali) support to Exynos5250 boards
  - Minor cleanup for Exynos3250 ADC
- Defconfig changes
  - Enable AHCI platform driver on exynos defconfig for Exynos5250-based Arndale board
  - Make Max77802 PIC regulator driver a built-in on multi_v7 defconfig
    as it is essential early during boot
Qualcomm
- ARM64 updates
  - Add video nodes, cpu coefficients, adsp, csdp, and
    fastrpc nodes for SDM845
  - Add coresight for MSM8996, SDM845, and MSM8998
  - Misc cleanups on QCS404 and PMS405
  - Update memory map for QCS404
  - Add wifi rails, update WCSS clocks, and add ADS unit names on QCS404
  - Initial support for Snapdragon 855 (SM8150) and SM8150 MTP reference platform
  - Enable CPU errata workarounds for Qualcomm Hydra/Kryo CPUs
- ARM updates
  - Add AOSS QMP support
  - Various fixups for Qualcomm SCM
  - Add socinfo driver
  - Add SoC serial number attribute and associated APIs
  - Add SM8150 and SC7180 support in Qualcomm SCM
  - Fixup max processor count in SMEM
- ARM64 defconfig changes
  - Enable Qualcomm MSM8916 clock drivers
  - Add DRM_MSM to ARCH_QCOM defconfigs
  - Enable Qualcomm SM8150 clock and pinctrl drivers
- New Platforms – Snapdragon 835 laptops: Asus NovaGo, HP Envy X2 and Lenovo Miix 630; Lenovo Yoga C630 Snapdragon 850 laptop; several Snapdragon 410 phones including Samsung A3/A5, Longcheer L8150
MediaTek
- Added support for Mediatek MT7629 wireless network router chip and reference platform
- Clock driver for Mediatek MT6779 SoC
- IOMMU Driver – MT8183 IOMMU support
- Regulator – Device support for Mediatek MT6358
Other new Arm hardware platforms and SoCs:
- NXP – NXP i.MX8M Nano SoC; i.MX8 boards: Einfochips i.MX8QXP AI_ML board, SolidRun Hummingboard Pulse baseboard and System-on-Module,
  Boundary Devices i.MX8MQ Nitrogen8M, and TechNexion
  PICO-PI-IMX8M-DEV. i.MX 6/7 boards: Kontron i.MX6UL N6310 SoM with two baseboards, the PHYTEC phyBOARD-Segin SoM with three baseboards, and the Zodiac Inflight Innovations i.MX7 RMU2 board. Layerscape LS1046A “Freeway” reference board

Changelog for MIPS architecture:

Main MIPS changes:
- boot_mem_map is removed, providing a nice cleanup made possible by the recent removal of bootmem.
- Some fixes to atomics, in general ,providing compiler barriers for smp_mb__{before,after}_atomic plus fixes specific to Loongson CPUs or MIPS32 systems using cmpxchg64().
- Conversion to the new generic VDSO infrastructure courtesy of Vincenzo Frascino.
- Removal of undefined behavior in set_io_port_base(), fixing the behavior of some MIPS kernel configurations when built with recent clang versions.
- Initial MIPS32 huge page support, functional on at least Ingenic SoCs.
- pte_special() is now supported for some configurations, allowing among other things generic fast GUP to be used.
- Miscellaneous fixes & cleanups.
Platform-specific changes:
- Major improvements to Ingenic SoC support from Paul Cercueil, mostly enabled by the inclusion of the new TCU (timer-counter unit) drivers he’s spent a very patient year or so working on. Plus some fixes for X1000 SoCs from Zhou Yanjie.
- Netgear R6200 v1 systems are now supported by the bcm47xx platform.
- DT updates for BMIPS, Lantiq & Microsemi Ocelot systems

Finally, a summary of changes made to RISC-V architecture:

New features:
- Generic CPU topology description support for DT-based platforms,
  including ARM64, ARM and RISC-V.
- Sparsemem support
- Perf callchain support
- SiFive PLIC irqchip modifications, in preparation for M-mode Linux
Clean ups:
- Clean up chip-specific register (CSR) manipulation code, IPIs, TLB
  flushing, and the RISC-V CPU-local timer code
- Kbuild cleanup from one of the Kbuild maintainers

Check out the complete Linux 5.4 changelog with comments generated using git log v5.3..v5.4-rc8 --stat command. For an even longer list of changes, visit 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.