MIPS: Loongson-3: Enable Store Fill Buffer at runtime

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).

[[email protected]: 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 <[email protected]>
Signed-off-by: Paul Burton <[email protected]>
Patchwork: https://patchwork.linux-mips.org/patch/20426/
Cc: Ralf Baechle <[email protected]>
Cc: James Hogan <[email protected]>
Cc: [email protected]
Cc: Fuxin Zhang <[email protected]>
Cc: Zhangjin Wu <[email protected]>
Cc: Huacai Chen <[email protected]>

0 files changed, 0 insertions, 0 deletions