[PATCH 1/3] ARM: dts: rainier: Add reserved memory for ramoops

[Joel Stanley]

On Fri, 2 Oct 2020 at 06:35, Andrew Jeffery <andrew at aj.id.au> wrote:
>
> Reserve a 1MiB region of memory to record kmsg dumps and console state
> into 16kiB ring-buffer slots. The sizing allows for up to 32 dumps to be
> captured and read out.
>
> Signed-off-by: Andrew Jeffery <andrew at aj.id.au>
> ---
>  arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts b/arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts
> index e6f422edf454..46a0e95049fd 100644
> --- a/arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts
> +++ b/arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts
> @@ -47,6 +47,14 @@ reserved-memory {
>                 #size-cells = <1>;
>                 ranges;
>
> +               ramoops at b7f00000 {
> +                       compatible = "ramoops";
> +                       reg = <0xb7f00000 0x100000>;
> +                       record-size = <0x4000>;
> +                       console-size = <0x4000>;

This is conserative. We've got plenty of space, how about we make it bigger?

$ git grep console-size *.dts* | grep -Po "0x([0-9]+)" | xargs printf
"%x\n" | sort -n
8000
8000
10000
10000
20000
20000
20000
20000
20000
60000
100000

The median is 128KB, which sounds reasonable.

$ git grep record-size *.dts* | grep -Po "0x([0-9]+)" | xargs printf "%x\n"
20000
400
400
20000
20000
20000
10000
10000
10000
10000
20000

64KB is the median record size.

> +                       pmsg-size = <0x4000>;

Do we want to add ftrace too?

Should we also add max-reason = KMSG_DUMP_EMERG?

Logging reboots and shutdowns is informative (you know if a reboot was
intentional or due to a crash that wasn't recorded) and allows for
testing.

Cheers,

Joel

> +               };
> +
>                 flash_memory: region at B8000000 {
>                         no-map;
>                         reg = <0xB8000000 0x04000000>; /* 64M */
> --
> 2.25.1
>