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[ Upstream commitd192615c30] The DSU PMU allows monitoring performance events in the DSU cluster, which is done by configuring and reading back values from the DSU PMU system registers. However, for write-access to be allowed by ELs lower than EL3, the EL3 firmware needs to update the setting on the ACTLR3_EL3 register, as it is disallowed by default. That configuration is not done on the firmware used by the MT8195 SoC, as a consequence, booting a MT8195-based machine like mt8195-cherry-tomato-r2 with CONFIG_ARM_DSU_PMU enabled hangs the kernel just as it writes to the CLUSTERPMOVSCLR_EL1 register, since the instruction faults to EL3, and BL31 apparently just re-runs the instruction over and over. Mark the DSU PMU node in the Devicetree with status "fail", as the machine doesn't have a suitable firmware to make use of it from the kernel, and allowing its driver to probe would hang the kernel. Fixes:37f2582883("arm64: dts: Add mediatek SoC mt8195 and evaluation board") Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> Link: https://lore.kernel.org/r/20230720200753.322133-1-nfraprado@collabora.com Link: https://lore.kernel.org/r/20231003-mediatek-fixes-v6-7-v1-5-dad7cd62a8ff@collabora.com Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.