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With the T-HEAD C9XX cores being designed before or during the ratification to the SSCOFPMF extension, it implements functionality very similar but not equal to it. It implements overflow handling and also some privilege-mode filtering. While SSCOFPMF supports this for all modes, the C9XX only implements the filtering for M-mode and S-mode but not user-mode. So add some adaptions to allow the C9XX to still handle its PMU through the regular SBI PMU interface instead of defining new interfaces or drivers. To work properly, this requires a matching change in SBI, though the actual interface between kernel and SBI does not change. The main differences are a the overflow CSR and irq number. As the reading of the overflow-csr is in the hot-path during irq handling, use an errata and alternatives to not introduce new conditionals there. Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Signed-off-by: Heiko Stuebner <heiko@sntech.de> Link: https://lore.kernel.org/all/20221011231841.2951264-2-heiko@sntech.de/ Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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.