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| author | Huacai Chen <chenhuacai@loongson.cn> | 2023-04-18 14:38:58 +0300 |
|---|---|---|
| committer | Huacai Chen <chenhuacai@loongson.cn> | 2023-04-18 14:38:58 +0300 |
| commit | 16c52e503043aed1e2a2ce38d9249de5936c1f6b (patch) | |
| tree | 7552a1e276d52b2cff4da4e8c7a0be030d4ce77a /Documentation/admin-guide | |
| parent | 6a8f57ae2eb07ab39a6f0ccad60c760743051026 (diff) | |
| download | linux-16c52e503043aed1e2a2ce38d9249de5936c1f6b.tar.xz | |
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 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 6 |
2 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst index 19600c50277b..6ae5f129fbca 100644 --- a/Documentation/admin-guide/kernel-parameters.rst +++ b/Documentation/admin-guide/kernel-parameters.rst @@ -128,6 +128,7 @@ parameter is applicable:: KVM Kernel Virtual Machine support is enabled. LIBATA Libata driver is enabled LP Printer support is enabled. + LOONGARCH LoongArch architecture is enabled. LOOP Loopback device support is enabled. M68k M68k architecture is enabled. These options have more detailed description inside of diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6221a1d057dd..7016cb12dc4e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6933,6 +6933,12 @@ When enabled, memory and cache locality will be impacted. + writecombine= [LOONGARCH] Control the MAT (Memory Access Type) of + ioremap_wc(). + + on - Enable writecombine, use WUC for ioremap_wc() + off - Disable writecombine, use SUC for ioremap_wc() + x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of default x2apic cluster mode on platforms supporting x2apic. |