linux-kernel - [RFC PATCH 1/3] MIPS: Loongson64: Clearify IO barriers

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Date:   Mon, 21 Feb 2022 14:55:29 +0000
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     linux-mips@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, chenhuacai@...nel.org,
        tsbogend@...ha.franken.de, macro@...am.me.uk,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: [RFC PATCH 1/3] MIPS: Loongson64: Clearify IO barriers

Remove CPU_HAS_WB from Kconfig as all Loongson64 processors
don't have R3000 style write buffer. This is likely to be
a legacy of Loongson 2E's Bonito64.

Remove Loongson64 from war_io_reorder_wmb. Loongson64
never reorders uncached memory access as per user manual
of GS464, LS3A2000 and LS3A3000. It was intruduced due
to a misunderstanding of Store Fill Buffer.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
---
 arch/mips/Kconfig          | 1 -
 arch/mips/include/asm/io.h | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 058446f01487..6d2e97342723 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -487,7 +487,6 @@ config MACH_LOONGSON64
 	select BOARD_SCACHE
 	select CSRC_R4K
 	select CEVT_R4K
-	select CPU_HAS_WB
 	select FORCE_PCI
 	select ISA
 	select I8259
diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
index 6f5c86d2bab4..065e1ab6401a 100644
--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -219,7 +219,7 @@ void iounmap(const volatile void __iomem *addr);
 #define ioremap_wc(offset, size)					\
 	ioremap_prot((offset), (size), boot_cpu_data.writecombine)
 
-#if defined(CONFIG_CPU_CAVIUM_OCTEON) || defined(CONFIG_CPU_LOONGSON64)
+#if defined(CONFIG_CPU_CAVIUM_OCTEON)
 #define war_io_reorder_wmb()		wmb()
 #else
 #define war_io_reorder_wmb()		barrier()
-- 
2.35.1