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Message-ID: <CAK9=C2U+H5xZaK6g5qcytESyC9H8gkU_jEUDJanEs1qzcGgYCQ@mail.gmail.com>
Date: Mon, 13 Oct 2025 09:13:02 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Bo Gan <ganboing@...il.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Greg KH <gregkh@...uxfoundation.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Ian Rogers <irogers@...gle.com>,
Alexandre Ghiti <alex@...ti.fr>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>, Liang Kan <kan.liang@...ux.intel.com>,
Mayuresh Chitale <mchitale@...il.com>, Anup Patel <anup@...infault.org>,
Atish Patra <atish.patra@...ux.dev>, Andrew Jones <ajones@...tanamicro.com>,
Sunil V L <sunilvl@...tanamicro.com>, linux-riscv@...ts.infradead.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
Mayuresh Chitale <mchitale@...tanamicro.com>
Subject: Re: [PATCH 04/11] rvtrace: Add functions to start/stop tracing on a
component path
On Wed, Oct 8, 2025 at 2:45 PM Bo Gan <ganboing@...il.com> wrote:
>
> On 10/1/25 23:07, Anup Patel wrote:
> > From: Mayuresh Chitale <mchitale@...tanamicro.com>
> >
> > The perf driver framework needs to be able to start / stop all components
> > in a trace component path during its operation. Add rvtrace_path_start()
> > and rvtrace_path_stop() functions for this purpose.
> >
> > Co-developed-by: Anup Patel <apatel@...tanamicro.com>
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> > Signed-off-by: Mayuresh Chitale <mchitale@...tanamicro.com>
> > ---
> > drivers/hwtracing/rvtrace/rvtrace-core.c | 44 ++++++++++++++++++++++++
> > include/linux/rvtrace.h | 6 ++++
> > 2 files changed, 50 insertions(+)
> >
> > diff --git a/drivers/hwtracing/rvtrace/rvtrace-core.c b/drivers/hwtracing/rvtrace/rvtrace-core.c
> > index 7013d50ca569..109be40d4b24 100644
> > --- a/drivers/hwtracing/rvtrace/rvtrace-core.c
> > +++ b/drivers/hwtracing/rvtrace/rvtrace-core.c
> > @@ -614,6 +614,50 @@ static void rvtrace_release_path_nodes(struct rvtrace_path *path)
> > }
> > }
> >
> > +int rvtrace_path_start(struct rvtrace_path *path)
> > +{
> > + const struct rvtrace_driver *rtdrv;
> > + struct rvtrace_component *comp;
> > + struct rvtrace_path_node *node;
> > + int ret;
> > +
> > + list_for_each_entry(node, &path->comp_list, head) {
> > + comp = node->comp;
> > + rtdrv = to_rvtrace_driver(comp->dev.driver);
> > + if (!rtdrv->start)
> > + continue;
> > +
> > + ret = rtdrv->start(comp);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(rvtrace_path_start);
> > +
> > +int rvtrace_path_stop(struct rvtrace_path *path)
> > +{
> > + const struct rvtrace_driver *rtdrv;
> > + struct rvtrace_component *comp;
> > + struct rvtrace_path_node *node;
> > + int ret;
> > +
> > + list_for_each_entry(node, &path->comp_list, head) {
> > + comp = node->comp;
> > + rtdrv = to_rvtrace_driver(comp->dev.driver);
> > + if (!rtdrv->stop)
> > + continue;
> > +
> > + ret = rtdrv->stop(comp);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(rvtrace_path_stop);
> > +
> > struct rvtrace_path *rvtrace_create_path(struct rvtrace_component *source,
> > struct rvtrace_component *sink,
> > enum rvtrace_component_mode mode)
> > diff --git a/include/linux/rvtrace.h b/include/linux/rvtrace.h
> > index f2174f463a69..e7bd335d388f 100644
> > --- a/include/linux/rvtrace.h
> > +++ b/include/linux/rvtrace.h
> > @@ -273,10 +273,14 @@ struct rvtrace_path *rvtrace_create_path(struct rvtrace_component *source,
> > struct rvtrace_component *sink,
> > enum rvtrace_component_mode mode);
> > void rvtrace_destroy_path(struct rvtrace_path *path);
> > +int rvtrace_path_start(struct rvtrace_path *path);
> > +int rvtrace_path_stop(struct rvtrace_path *path);
> >
> > /**
> > * struct rvtrace_driver - Representation of a RISC-V trace driver
> > * id_table: Table to match components handled by the driver
> > + * start: Callback to start tracing
> > + * stop: Callback to stop tracing
> > * probe: Driver probe() function
> > * remove: Driver remove() function
> > * get_trace_id: Get/allocate a trace ID
> > @@ -285,6 +289,8 @@ void rvtrace_destroy_path(struct rvtrace_path *path);
> > */
> > struct rvtrace_driver {
> > const struct rvtrace_component_id *id_table;
> > + int (*start)(struct rvtrace_component *comp);
> > + int (*stop)(struct rvtrace_component *comp);
> > int (*probe)(struct rvtrace_component *comp);
> > void (*remove)(struct rvtrace_component *comp);
> > int (*get_trace_id)(struct rvtrace_component *comp,
>
> I'd suggest add another function (*quiesce) or something like that. Trace
> components have a tr??Empty bit that indicates trace has been all flushed
> out. Also along the path when you do rvtrace_path_stop, you need to ensure
> the source has stopped and quiescent before beginning to stop the sink.
> Otherwise you'll get partial or corrupted trace. In essence, follow Control
> Interface Spec 11.3 Enabling and Disabling. FYI: my userspace driver:
> https://github.com/ganboing/riscv-trace-umd/blob/master/rvtrace/funnel.py#L223
It's better to add functions on a need basis rather than adding
it now without any potential user.
Regards,
Anu
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