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MIPS: Loongson64: Remove CPU_HAS_WB

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Q: Do we have really have write buffer
A: Yes, on newer Loongson processors there is a "store fill buffer"
   that will collect *cached* writes, on all Loongson processors
   AXI crossbar will buffer all writes.

Q: Then why do we want to remove CPU_HAS_WB?
A: Because CPU_HAS_WB introduces wbflush, which intends to flush
   all write reuqests to mmio device. We won't be affected by store
   fill buffer because it won't buffer uncached writes. And a regular
   memory barrier is sufficient to flush crossbar write buffer.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
This commit is contained in:
Jiaxun Yang 2023-02-21 13:16:57 +00:00 committed by Thomas Bogendoerfer
parent 227003cb53
commit 162e134aed
2 changed files with 0 additions and 16 deletions
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1
arch/mips/Kconfig
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@ -490,7 +490,6 @@ config MACH_LOONGSON64
select BOARD_SCACHE
select CSRC_R4K
select CEVT_R4K
select CPU_HAS_WB
select FORCE_PCI
select ISA
select I8259

15
arch/mips/loongson64/setup.c
View File

@ -6,7 +6,6 @@
#include <linux/export.h>
#include <linux/init.h>
#include <asm/wbflush.h>
#include <asm/bootinfo.h>
#include <linux/libfdt.h>
#include <linux/of_fdt.h>
@ -17,20 +16,6 @@
void *loongson_fdt_blob;
static void wbflush_loongson(void)
{
asm(".set\tpush\n\t"
".set\tnoreorder\n\t"
".set mips3\n\t"
"sync\n\t"
"nop\n\t"
".set\tpop\n\t"
".set mips0\n\t");
}
void (*__wbflush)(void) = wbflush_loongson;
EXPORT_SYMBOL(__wbflush);
void __init plat_mem_setup(void)
{
if (loongson_fdt_blob)