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authorYijie Yang <yijie.yang@oss.qualcomm.com>2026-08-11 16:46:47 +0800
committerRob Herring (Arm) <robh@kernel.org>2026-08-15 15:46:52 -0500
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tree61c2297688373db165cc857b7c7adcb147a5c419 /Documentation/arch/powerpc/elfnote.rst
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dt-bindings: interconnect: qcom-bwmon: Add Maili cpu-bwmon compatiblegrafted
Add the Qualcomm Maili SoC compatible string for the CPU bandwidth monitor (BWMONv4). This falls back to the sdm845-bwmon compatible, consistent with the existing pattern used by other recent SoCs such as sm8750 and kaanapali. Signed-off-by: Yijie Yang <yijie.yang@oss.qualcomm.com> Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com> Reviewed-by: Jingyi Wang <jingyi.wang@oss.qualcomm.com> Link: https://patch.msgid.link/20260811-bwmon-v2-1-80f7f150ab9e@oss.qualcomm.com Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
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+==========================
+ELF Note PowerPC Namespace
+==========================
+
+The PowerPC namespace in an ELF Note of the kernel binary is used to store
+capabilities and information which can be used by a bootloader or userland.
+
+Types and Descriptors
+---------------------
+
+The types to be used with the "PowerPC" namespace are defined in [#f1]_.
+
+ 1) PPC_ELFNOTE_CAPABILITIES
+
+Define the capabilities supported/required by the kernel. This type uses a
+bitmap as "descriptor" field. Each bit is described below:
+
+- Ultravisor-capable bit (PowerNV only).
+
+.. code-block:: c
+
+ #define PPCCAP_ULTRAVISOR_BIT (1 << 0)
+
+Indicate that the powerpc kernel binary knows how to run in an
+ultravisor-enabled system.
+
+In an ultravisor-enabled system, some machine resources are now controlled
+by the ultravisor. If the kernel is not ultravisor-capable, but it ends up
+being run on a machine with ultravisor, the kernel will probably crash
+trying to access ultravisor resources. For instance, it may crash in early
+boot trying to set the partition table entry 0.
+
+In an ultravisor-enabled system, a bootloader could warn the user or prevent
+the kernel from being run if the PowerPC ultravisor capability doesn't exist
+or the Ultravisor-capable bit is not set.
+
+References
+----------
+
+.. [#f1] arch/powerpc/include/asm/elfnote.h
+