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Commit 4419da5d authored by Shanker Donthineni's avatar Shanker Donthineni Committed by Greg Kroah-Hartman
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tty: hvc: dcc: Bind driver to CPU core0 for reads and writes



Some external debuggers do not handle reads/writes from/to DCC
on secondary cores. Each core has its own DCC device registers,
so when a core reads or writes from/to DCC, it only accesses
its own DCC device. Since kernel code can run on any core,
every time the kernel wants to write to the console, it might
write to a different DCC.

In SMP mode, external debugger creates 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.

Selecting this debug option will enable code that serializes all
console input and output to core 0. The DCC driver will create
input and output FIFOs that all cores will use. Reads and writes
from/to DCC are handled by a workqueue that runs only core 0.

This is a debug feature to be used only in early stage development
where debug serial console support would not be present. It disables
PM feature like CPU hotplug and is not suitable for production
environment.

Signed-off-by: default avatarShanker Donthineni <shankerd@codeaurora.org>
Acked-by: default avatarAdam Wallis <awallis@codeaurora.org>
Signed-off-by: default avatarTimur Tabi <timur@codeaurora.org>
Signed-off-by: default avatarElliot Berman <eberman@codeaurora.org>
Signed-off-by: default avatarSai Prakash Ranjan <quic_saipraka@quicinc.com>
Link: https://lore.kernel.org/r/20220428090858.14489-1-quic_saipraka@quicinc.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6808b7f5
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