[Skiboot] [PATCH 08/15] core/trace: Export trace buffers to sysfs

[Oliver]

On Mon, Mar 25, 2019 at 11:18 AM Jordan Niethe <jniethe5 at gmail.com> wrote:
>
> Every property in the device tree under /ibm,opal/firmware/exports has a
> sysfs node created in /firmware/opal/exports. Add properties with the
> physical address and size for each trace buffer so they are exported.
> ---
>  core/test/run-trace.c |  1 +
>  core/trace.c          | 10 ++++++++++
>  2 files changed, 11 insertions(+)
>
> diff --git a/core/test/run-trace.c b/core/test/run-trace.c
> index 971b967a5719..6cb9a582078d 100644
> --- a/core/test/run-trace.c
> +++ b/core/test/run-trace.c
> @@ -269,6 +269,7 @@ int main(void)
>         unsigned int i, j;
>
>         opal_node = dt_new_root("opal");
> +       dt_new(dt_new(opal_node, "firmware"), "exports");
>         for (i = 0; i < CPUS; i++) {
>                 fake_cpus[i].server_no = i;
>                 fake_cpus[i].is_secondary = (i & 0x1);
> diff --git a/core/trace.c b/core/trace.c
> index b33a5bcf2318..dfb5cfad045c 100644
> --- a/core/trace.c
> +++ b/core/trace.c
> @@ -19,6 +19,7 @@
>  #include <lock.h>
>  #include <string.h>
>  #include <stdlib.h>
> +#include <inttypes.h>
>  #include <cpu.h>
>  #include <device.h>
>  #include <libfdt.h>
> @@ -163,12 +164,21 @@ static void trace_add_dt_props(void)
>  {
>         unsigned int i;
>         u64 *prop, tmask;
> +       struct dt_node *exports;
> +       char tname[256];
>
>         prop = malloc(sizeof(u64) * 2 * debug_descriptor.num_traces);
>
> +       exports = dt_find_by_path(opal_node, "firmware/exports");
>         for (i = 0; i < debug_descriptor.num_traces; i++) {
>                 prop[i * 2] = cpu_to_fdt64(debug_descriptor.trace_phys[i]);
>                 prop[i * 2 + 1] = cpu_to_fdt64(debug_descriptor.trace_size[i]);
> +
> +               snprintf(tname, sizeof(tname), "trace-%x-%"PRIx64,
> +                        debug_descriptor.trace_cpu[i],
> +                        debug_descriptor.trace_phys[i]);
> +               dt_add_property_u64s(exports, tname, debug_descriptor.trace_phys[i],
> +                        debug_descriptor.trace_size[i]);

This is going to be a bit spammy especially on the bigger systems. A
dual socket P9 can have up to 44 cores so we're going to have a fair
amount of junk in there. It would be nice if we could have some kind
of categorisation, (e.g. subnodes that turn into subdirectories of
exports/), but that would require a kernel change. Maybe a nvram
option to flatten the exports directory would do the trick? Stewart,
what do you think?

Code looks fine though.

>         }
>
>         dt_add_property(opal_node, "ibm,opal-traces",
> --
> 2.20.1
>
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