diff options
| author | Huacai Chen <chenhuacai@loongson.cn> | 2023-04-18 19:38:58 +0800 |
|---|---|---|
| committer | Huacai Chen <chenhuacai@loongson.cn> | 2023-04-18 19:38:58 +0800 |
| commit | 16c52e503043aed1e2a2ce38d9249de5936c1f6b (patch) | |
| tree | 7552a1e276d52b2cff4da4e8c7a0be030d4ce77a /arch/loongarch/Kconfig | |
| parent | 6a8f57ae2eb07ab39a6f0ccad60c760743051026 (diff) | |
LoongArch: Make WriteCombine configurable for ioremap()
LoongArch maintains cache coherency in hardware, but when paired with
LS7A chipsets the WUC attribute (Weak-ordered UnCached, which is similar
to WriteCombine) is out of the scope of cache coherency machanism for
PCIe devices (this is a PCIe protocol violation, which may be fixed in
newer chipsets).
This means WUC can only used for write-only memory regions now, so this
option is disabled by default, making WUC silently fallback to SUC for
ioremap(). You can enable this option if the kernel is ensured to run on
hardware without this bug.
Kernel parameter writecombine=on/off can be used to override the Kconfig
option.
Cc: stable@vger.kernel.org
Suggested-by: WANG Xuerui <kernel@xen0n.name>
Reviewed-by: WANG Xuerui <kernel@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Diffstat (limited to 'arch/loongarch/Kconfig')
| -rw-r--r-- | arch/loongarch/Kconfig | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig index 7fd51257e0ed..3ddde336e6a5 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -447,6 +447,22 @@ config ARCH_IOREMAP protection support. However, you can enable LoongArch DMW-based ioremap() for better performance. +config ARCH_WRITECOMBINE + bool "Enable WriteCombine (WUC) for ioremap()" + help + LoongArch maintains cache coherency in hardware, but when paired + with LS7A chipsets the WUC attribute (Weak-ordered UnCached, which + is similar to WriteCombine) is out of the scope of cache coherency + machanism for PCIe devices (this is a PCIe protocol violation, which + may be fixed in newer chipsets). + + This means WUC can only used for write-only memory regions now, so + this option is disabled by default, making WUC silently fallback to + SUC for ioremap(). You can enable this option if the kernel is ensured + to run on hardware without this bug. + + You can override this setting via writecombine=on/off boot parameter. + config ARCH_STRICT_ALIGN bool "Enable -mstrict-align to prevent unaligned accesses" if EXPERT default y |