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The recommended flow for stall-on-fault in SMMUv2 is the following: 1. Resolve the fault. 2. Write to FSR to clear the fault bits. 3. Write RESUME to retry or fail the transaction. MMU500 is designed with this sequence in mind. For example, experimentally we have seen on MMU500 that writing RESUME does not clear FSR.SS unless the original fault is cleared in FSR, so 2 must come before 3. FSR.SS is allowed to signal a fault (and does on MMU500) so that if we try to do 2 -> 1 -> 3 (while exiting from the fault handler after 2) we can get duplicate faults without hacks to disable interrupts. However, resolving the fault typically requires lengthy operations that can stall, like bringing in pages from disk. The only current user, drm/msm, dumps GPU state before failing the transaction which indeed can stall. Therefore, from now on we will require implementations that want to use stall-on-fault to also enable threaded IRQs. Do that with the Adreno MMU implementations. Signed-off-by: Connor Abbott <cwabbott0@gmail.com> Link: https://lore.kernel.org/r/20250520-msm-gpu-fault-fixes-next-v8-1-fce6ee218787@gmail.com Signed-off-by: Will Deacon <will@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 reStructuredText 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.