[Skiboot] [PATCH] doc: Document ibm,heartbeat-ms

[Oliver]

On Tue, Apr 3, 2018 at 2:57 PM, Stewart Smith <stewart at linux.ibm.com> wrote:
> and by 'document', I mean 'gather a few extra minor bits of breadcrumbs
> of clues as to what, when and why this thing exists'.
>
> Signed-off-by: Stewart Smith <stewart at linux.ibm.com>
> ---
>  doc/device-tree/ibm,opal.rst | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/doc/device-tree/ibm,opal.rst b/doc/device-tree/ibm,opal.rst
> index 932f41d05cde..2fa446ddef04 100644
> --- a/doc/device-tree/ibm,opal.rst
> +++ b/doc/device-tree/ibm,opal.rst
> @@ -50,3 +50,24 @@ Top level ibm,opal node
>                 opal-runtime-size = <0x0 0x9a00000>;
>                 phandle = <0x10000003>;
>      };
> +
> +.. ibm-heartbeat-ms:
> +
> +ibm,heartbeat-ms
> +^^^^^^^^^^^^^^^^
> +
> +.. code-block:: dts
> +
> +   ibm,opal {
> +               ibm,heartbeat-ms = <0x7d0>;
> +   }
> +
> +
> +Any OS targetting POWER9 processors *must* respect `ibm,heartbeat-ms`.
> +
> +Linux kernels prior to v4.1-rc1 would ignore `ibm,heartbeat-ms`. These only
> +supported POWER8 systems.
> +
> +On the earliest POWER8 OPAL systems, there was `ibm,heartbeat-freq` instead.
> +However, no OS at the time ever looked at that value, so it can be ignored
> +by any new operating systems.

Doesn't this set the interval between calls to OPAL_POLL_EVENTS? I
think as a side effect
we also run the pollers inside of skiboot so you need it to make
centaur I2C work too.

We should probably document that :)

> --
> 2.14.3
>
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