CONFIG_HVC_DCC_SERIALIZE_SMP: Use DCC only on CPU core 0

General informations

The Linux kernel configuration item CONFIG_HVC_DCC_SERIALIZE_SMP:

• prompt: Use DCC only on CPU core 0
• type: bool
• depends on: CONFIG_SMP && CONFIG_HVC_DCC
• defined in drivers/tty/hvc/Kconfig
• found in Linux kernels: 5.19, 6.0–6.8, 6.9-rc+HEAD

Help text

This is a DEBUG option to serialize all console input and output to CPU 0. Some external debuggers, do not handle reads/writes from/to DCC on more than one CPU core. Each core has its own DCC device registers, so when a CPU core reads or writes from/to DCC, it only accesses its own DCC device. Since kernel code can run on any CPU core, every time the kernel wants to write to the console, it might write to a different DCC.

In SMP mode, external debuggers create multiple windows, and each window shows the DCC output only from that core's DCC. The result is that console output is either lost or scattered across windows.

Enable this option only if you are sure that you do not need features like CPU hotplug to work. For example, during early chipset bringups without debug serial console support. If unsure, say N.

Hardware

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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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