[Skiboot] [PATCH v2 1/5] skiboot/doc: Add documentation for trace-mode in imc.rst

Stewart Smith stewart at linux.vnet.ibm.com
Mon Feb 25 14:57:09 AEDT 2019

Anju T Sudhakar <anju at linux.vnet.ibm.com> writes:
> Add documentation for IMC trace-mode in imc.rst.
> Signed-off-by: Anju T Sudhakar <anju at linux.vnet.ibm.com>
> ---
>  doc/imc.rst | 9 +++++++++
>  1 file changed, 9 insertions(+)
> diff --git a/doc/imc.rst b/doc/imc.rst
> index 3324aa36..40d262f0 100644
> --- a/doc/imc.rst
> +++ b/doc/imc.rst
> @@ -44,6 +44,15 @@ sampling duration) fetches the counter data and accumulate to main memory.
>  Memory to accumulate counter data are refered from "PDBAR" (per-core scom)
>  and "LDBAR" per-thread spr.
> +Trace mode of IMC:
> +------------------
> +
> +POWER9 support two modes for IMC which are the Accumulation mode and
> +Trace mode. In IMC Trace mode, event counted is fixed for cycles and on
> +each overflow, hardware snapshots the program counter along with other
> +details and writes into memory pointed by LDBAR. LDBAR has bits to
> +indicate the IMC trace-mode.
> +

I'm having trouble parsing what's being said here.

I can't understand what "event counted is fixed for cycles" means, nor
what overflow is being referred to.

This needs to be reworded so it's clear as to what's going on and what
the trace mode means and does.

Stewart Smith
OPAL Architect, IBM.

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