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| author | Huacai Chen <chenhuacai@loongson.cn> | 2023-04-18 19:38:58 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-04-26 14:30:07 +0200 |
| commit | 9d9f5b437684d2e0d613332df711a4fdd1188885 (patch) | |
| tree | 05cbbc273ddd1ab3cfa31015ee367aaaa9c2f659 /Documentation | |
| parent | 13e28ed3bfbb474a511e9cfdb92180ec53568247 (diff) | |
| download | linux-stable-9d9f5b437684d2e0d613332df711a4fdd1188885.tar.gz linux-stable-9d9f5b437684d2e0d613332df711a4fdd1188885.tar.bz2 linux-stable-9d9f5b437684d2e0d613332df711a4fdd1188885.zip | |
LoongArch: Make WriteCombine configurable for ioremap()
commit 16c52e503043aed1e2a2ce38d9249de5936c1f6b upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation')
| -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 959f73a32712..426440f5d79f 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 6cfa6e3996cf..8cf1595545ac 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6874,6 +6874,12 @@ 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. |