The kernel 6.15 has been released and with it comes the support for new hardware, improved security, and optimizations. A full list of the changes is available here.

Here are some key changes:

• New hardware support: AMD Zen 6 cores (preparing for future Ryzen and EPYC processor support), RISC-V support for BFloat16, UBSAN support for LoongArch, Intel and AMD KVM updates
• Improvements on graphics drivers and the first Rust-based NVIDIA kernel graphics/display driver (NOVA)
• Various performance improvements, like the new Zstd version

As always, this new version includes contributions from Collabora. We have no less than 20 authored contributors on this release, aiming at improving Rockchip and Mediatek support in the Linux kernel!

Here are the highlights and the full list can be found below.

MediaTek

During a round of bug hunting and cleanups, AngeloGioacchino Del Regno found multiple issues in the MediaTek Display Controller components routing in the Multimedia Subsystem. Specifically, multiple SoCs' routing tables had mismatching register mask - register value pairs for multiple entries, rendering a few or all Display Controller outputs unusable. For example, screen output on MT8365 Genio 350 boards was broken, as much as the output path to HDMI on MT8370 Genio 510 and MT8190 Genio 700.

After fixing all of the routing table entries for all of the upstream MediaTek SoCs, he converted them all to use his newly introduced MMSYS_ROUTE() macro, performing compile-time tests to make sure that the single table entries' register value fits into the declared register mask.

Angelo also introduced a few new features and completed support for pending ones.

He was able to finally use his Display Controller OF Graph support infrastructure by adding full Display Controller graphs into MT8188 and MT8195 Chromebooks, and in MT8170, MT8390, and MT8395 Genio device trees, allowing boards with the same SoC, but delivering different display output capabilities, to coexist in the upstream kernels.

He also added support for all of the USB, MicroUSB, and Type-C ports, including the ones with USB Power Delivery capability, for USB Host and Gadget modes on all of the newly supported ports, and for the tertiary MSDC Controller (usually targeted at SDIO devices) on the MT8190 MediaTek Genio 700 EVK.

Last but not least, he added support for the Digital Parallel Interface (DPI) controller found on MT8195, MT8188, MT8370, MT8390, MT8195 SoCs, used for routing display output to HDMI displays, including code to enable its internal Pattern Generator on-demand for debugging purposes, and worked on cleaning up the old MediaTek HDMI Controller driver, paving the way to add support for the new HDMI v2.0b Transmitter Controller found in the aforementioned SoCs.

Louis-Alexis Eyraud has been improving network interface support for Genio 350 EVK board and added support for MT8370 SoC and Genio 510 EVK board.

Nícolas F. R. A. Prado has been improving thermal sensor support as well as adding audio support on MT8188.

Julien Massot added support for a display panel on the Radxa NIO 12L via a device tree overlay.

Rockchip

Cristian Ciocaltea added support for the second HDMI port on the RK3588 SoCs family. He also improved the selection of clock providers in the HDMI driver to achieve better output clock accuracy and support more frame rate outputs. Note that the maximum supported resolution is currently 4K@30Hz. Anything above, e.g., 4K@60Hz, requires a high TMDS clock ratio and scrambling support, which would enable HDMI 2.0 display modes by allowing TMDS character rates to exceed the 340MHz limit of HDMI 1.4b.

Detlev Casanova added support for the not yet released RK3576-based Radxa ROCK 4D. He also added support for HDMI audio on the RK3588 SoCs. It uses new DRM interfaces to ease setting up drm bridges based audio codecs.

Dmitry Osipenko and Shreeya Patel brought support for HDMI RX on the RK3588 SoC, allowing the capture of HDMI streams.

Nicolas Frattaroli has been generally improving RK3576 and ArmSoM Sige5 support. He also added support for the RK3588 Random Number Generator, which produces around 30 Mbit/s of clean, crisp randomness. This is especially useful during early boot, where the kernel has not yet had much time to generate its own entropy from variations in timers and such, but needs to provide high quality random numbers for various cryptographic applications.

Sebastian Reichel improved the error handling in the Rockchip power-domain driver and added support for regulator handling. This is needed to properly handle the GPU power-domain. Until now, the GPU driver has enabled the power domain and ensured that the regulator is enabled. But enabling the power-domain while the regulator is disabled results in a fatal system error. The regulator is enabled at boot time, so by probing the GPU driver early enough, the system error could be avoided. But if something slows down the boot or if the driver is reloaded later, the system would die until now.

Apart from that, Sebastian wrote and upstreamed a new driver for the Wanchanglong W552793BAA DSI panel, which is used by the RK3588 evaluation board. This will become useful in combination with the DSI driver, which Heiko Stübner took care of and which also landed in this release with just the device-tree changes missing.

Here, there, and everywhere

On the hardware enablement front, Julien added support for the MYIR Remi Pi board, an SBC powered by the Renesas RZ/G2L processor. This board was featured at our booth at Embedded World earlier this year, where it demonstrated machine learning video analytics with GStreamer. On the graphics side, Adrián continued his work on Panthor, the open source kernel driver for Arm Mali GPUs. He improved the driver's locking and added information exposed by the driver.

Below is a full list of contributions made by Collabora for the 6.15 release, as recorded in the git commit history:

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