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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).

[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>
hifive-unleashed-5.1
Huacai Chen 2018-09-05 17:33:01 +08:00 committed by Paul Burton
parent 2794f688b2
commit c824ad1647
No known key found for this signature in database
GPG Key ID: 3EA79FACB57500DD
2 changed files with 13 additions and 5 deletions
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2
arch/mips/include/asm/io.h
View File

@ -289,7 +289,7 @@ static inline void iounmap(const volatile void __iomem *addr)
#undef __IS_KSEG1
}
#if defined(CONFIG_CPU_CAVIUM_OCTEON) || defined(CONFIG_LOONGSON3_ENHANCEMENT)
#if defined(CONFIG_CPU_CAVIUM_OCTEON) || defined(CONFIG_CPU_LOONGSON3)
#define war_io_reorder_wmb() wmb()
#else
#define war_io_reorder_wmb() barrier()

16
arch/mips/include/asm/mach-loongson64/kernel-entry-init.h
View File

@ -11,6 +11,8 @@
#ifndef __ASM_MACH_LOONGSON64_KERNEL_ENTRY_H
#define __ASM_MACH_LOONGSON64_KERNEL_ENTRY_H
#include <asm/cpu.h>
/*
* Override macros used in arch/mips/kernel/head.S.
*/
@ -26,12 +28,15 @@
mfc0 t0, CP0_PAGEGRAIN
or t0, (0x1 << 29)
mtc0 t0, CP0_PAGEGRAIN
#ifdef CONFIG_LOONGSON3_ENHANCEMENT
/* Enable STFill Buffer */
mfc0 t0, CP0_PRID
andi t0, (PRID_IMP_MASK | PRID_REV_MASK)
slti t0, (PRID_IMP_LOONGSON_64 | PRID_REV_LOONGSON3A_R2)
bnez t0, 1f
mfc0 t0, CP0_CONFIG6
or t0, 0x100
mtc0 t0, CP0_CONFIG6
#endif
1:
_ehb
.set pop
#endif
@ -52,12 +57,15 @@
mfc0 t0, CP0_PAGEGRAIN
or t0, (0x1 << 29)
mtc0 t0, CP0_PAGEGRAIN
#ifdef CONFIG_LOONGSON3_ENHANCEMENT
/* Enable STFill Buffer */
mfc0 t0, CP0_PRID
andi t0, (PRID_IMP_MASK | PRID_REV_MASK)
slti t0, (PRID_IMP_LOONGSON_64 | PRID_REV_LOONGSON3A_R2)
bnez t0, 1f
mfc0 t0, CP0_CONFIG6
or t0, 0x100
mtc0 t0, CP0_CONFIG6
#endif
1:
_ehb
.set pop
#endif