CONFIG_ARCH_WRITECOMBINE: Enable WriteCombine (WUC) for ioremap()

General informations

The Linux kernel configuration item CONFIG_ARCH_WRITECOMBINE:

• prompt: Enable WriteCombine (WUC) for ioremap()
• type: bool
• depends on: (none)
• defined in arch/loongarch/Kconfig
• found in Linux kernels: 6.3–6.8, 6.9-rc+HEAD

Help text

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.

Hardware

LKDDb

Raw data from LKDDb:

• (none)

Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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