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New Loongson-3 (Loongson-3A R2, Loongson-3A R3, and newer) has SFB (Store Fill Buffer) which can improve the performance of memory access. Now, SFB enablement is controlled by CONFIG_LOONGSON3_ENHANCEMENT, and the generic kernel has no benefit from SFB (even it is running on a new Loongson-3 machine). With this patch, we can enable SFB at runtime by detecting the CPU type (the expense is war_io_reorder_wmb() will always be a 'sync', which will hurt the performance of old Loongson-3). [paul.burton@mips.com: Further info from Huacai: In practise, I found that sometimes there are boot failures if I enable SFB/LPA in cpu_probe(). I don't know why because processor designers also haven't give me an explaination, but I think this may have some relationships to speculative execution.] Signed-off-by: Huacai Chen <chenhc@lemote.com> Signed-off-by: Paul Burton <paul.burton@mips.com> Patchwork: https://patchwork.linux-mips.org/patch/20426/ Cc: Ralf Baechle <ralf@linux-mips.org> Cc: James Hogan <jhogan@kernel.org> Cc: linux-mips@linux-mips.org Cc: Fuxin Zhang <zhangfx@lemote.com> Cc: Zhangjin Wu <wuzhangjin@gmail.com> Cc: Huacai Chen <chenhuacai@gmail.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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.