Add documentation for the powerpc memtrace debugfs files

CONFIG_PPC_MEMTRACE must be set to use this feature. This can only be
used on powernv platforms.

Signed-off-by: Rashmica Gupta <rashmica.g@gmail.com>
[mpe: Update dates and kernel versions, mention size is in bytes]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/Documentation/ABI/testing/ppc-memtrace b/Documentation/ABI/testing/ppc-memtrace
new file mode 100644 (file)
index 0000000..2e8b937
--- /dev/null
+++ b/Documentation/ABI/testing/ppc-memtrace
@@ -0,0 +1,45 @@
+What:          /sys/kernel/debug/powerpc/memtrace
+Date:          Aug 2017
+KernelVersion: 4.14
+Contact:       linuxppc-dev@lists.ozlabs.org
+Description:   This folder contains the relevant debugfs files for the
+               hardware trace macro to use. CONFIG_PPC64_HARDWARE_TRACING
+               must be set.
+
+What:          /sys/kernel/debug/powerpc/memtrace/enable
+Date:          Aug 2017
+KernelVersion: 4.14
+Contact:       linuxppc-dev@lists.ozlabs.org
+Description:   Write an integer containing the size in bytes of the memory
+               you want removed from each NUMA node to this file - it must be
+               aligned to the memblock size. This amount of RAM will be removed
+               from the kernel mappings and the following debugfs files will be
+               created. This can only be successfully done once per boot. Once
+               memory is successfully removed from each node, the following
+               files are created.
+
+What:          /sys/kernel/debug/powerpc/memtrace/<node-id>
+Date:          Aug 2017
+KernelVersion: 4.14
+Contact:       linuxppc-dev@lists.ozlabs.org
+Description:   This directory contains information about the removed memory
+               from the specific NUMA node.
+
+What:          /sys/kernel/debug/powerpc/memtrace/<node-id>/size
+Date:          Aug 2017
+KernelVersion: 4.14
+Contact:       linuxppc-dev@lists.ozlabs.org
+Description:   This contains the size of the memory removed from the node.
+
+What:          /sys/kernel/debug/powerpc/memtrace/<node-id>/start
+Date:          Aug 2017
+KernelVersion: 4.14
+Contact:       linuxppc-dev@lists.ozlabs.org
+Description:   This contains the start address of the removed memory.
+
+What:          /sys/kernel/debug/powerpc/memtrace/<node-id>/trace
+Date:          Aug 2017
+KernelVersion: 4.14
+Contact:       linuxppc-dev@lists.ozlabs.org
+Description:   This is where the hardware trace macro will output the trace
+               it generates.