powerpc: Document sysfs DSCR interface

Add some documentation about ...

/sys/devices/system/cpu/dscr_default
/sys/devices/system/cpu/cpuN/dscr

... to Documentation/ABI/stable.

Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Sam bobroff 2014-05-21 16:32:39 +10:00 committed by Benjamin Herrenschmidt
parent 1739ea9e13
commit 26c88f9301
1 changed files with 25 additions and 0 deletions

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What: /sys/devices/system/cpu/dscr_default
Date: 13-May-2014
KernelVersion: v3.15.0
Contact:
Description: Writes are equivalent to writing to
/sys/devices/system/cpu/cpuN/dscr on all CPUs.
Reads return the last written value or 0.
This value is not a global default: it is a way to set
all per-CPU defaults at the same time.
Values: 64 bit unsigned integer (bit field)
What: /sys/devices/system/cpu/cpu[0-9]+/dscr
Date: 13-May-2014
KernelVersion: v3.15.0
Contact:
Description: Default value for the Data Stream Control Register (DSCR) on
a CPU.
This default value is used when the kernel is executing and
for any process that has not set the DSCR itself.
If a process ever sets the DSCR (via direct access to the
SPR) that value will be persisted for that process and used
on any CPU where it executes (overriding the value described
here).
If set by a process it will be inherited by child processes.
Values: 64 bit unsigned integer (bit field)