Samsung Exynos ACPM firmware mailbox protocol
Communication glue for the Adaptive Clock and Power Manager, a small dedicated firmware controller inside Samsung Exynos and Google Tensor mobile chips that handles power-management, voltage scaling, and PMIC requests on behalf of the main CPUs. It is currently used by Google's Tensor GS101 generation, which shipped in the Pixel 6, 6 Pro, and 6a phones.
recommendation
It should stay because the code is actively maintained, was only added to the kernel in 2025, and received further work as recently as October 2025 adding ACPM clock device support. Although its hardware footprint is narrow, limited to GS101-era Pixel phones that are no longer sold new but remain under Google software support through 2027, there is no replacement and removing it would break those devices.
repository signals
sources
- git.kernel.org
Latest substantive upstream work in this directory was in October 2025, adding ACPM clock device registration, which is evidence of active maintenance rather than removal.
- git.kernel.org
The driver was introduced recently, in 2025, so it is not legacy code aging out of the tree.
- cateee.net
LKDDb ties this driver to CONFIG_EXYNOS_ACPM_PROTOCOL and specifically lists the DT compatible google,gs101-acpm-ipc, indicating a narrow deployment footprint centered on GS101-class devices.
- support.google.com
Google's Pixel update page shows Pixel 6a remains supported for software updates into 2027, which supports a conclusion of ongoing but limited active deployments today.
codex reasoning notes (technical)
Real driver directory, not helper-only code: local inspection with exec_command showed module_platform_driver() and MODULE_DESCRIPTION("Samsung Exynos ACPM mailbox protocol driver") in exynos-acpm.c plus PMIC/DVFS protocol code. Upstream activity was checked with exec_command using local git log on the directory; it showed a continuous 2025 patch stream and no removal/deprecation-themed commits, so there is no sign of active removal talk. LKDDb URL was obtained via web search and confirms the only listed DT compatible is google,gs101-acpm-ipc, pointing to a narrow GS101/Tensor-era phone deployment rather than broad new hardware sales. The Google support URL is a canonical recall used only to justify that devices are still in service; combined with the GS101-specific match, that supports keep/no replacement, with low current deployments and no evidence the hardware is still sold new in 2025.