linux-kernel - Re: [PATCH v7 01/15] coresight: trace-id: Add API to dynamically assign Trace ID values

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Message-ID: <1896a73b-eb7b-7ffb-272d-115a10adeb71@arm.com>
Date:   Mon, 16 Jan 2023 14:16:39 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Mike Leach <mike.leach@...aro.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     mathieu.poirier@...aro.org, peterz@...radead.org, mingo@...hat.com,
        acme@...nel.org, linux-perf-users@...r.kernel.org,
        leo.yan@...aro.org, quic_jinlmao@...cinc.com
Subject: Re: [PATCH v7 01/15] coresight: trace-id: Add API to dynamically
 assign Trace ID values

Hi Mike

On 16/01/2023 12:49, Mike Leach wrote:
> The existing mechanism to assign Trace ID values to sources is limited
> and does not scale for larger multicore / multi trace source systems.
> 
> The API introduces functions that reserve IDs based on availabilty
> represented by a coresight_trace_id_map structure. This records the
> used and free IDs in a bitmap.
> 
> CPU bound sources such as ETMs use the coresight_trace_id_get_cpu_id
> coresight_trace_id_put_cpu_id pair of functions. The API will record
> the ID associated with the CPU. This ensures that the same ID will be
> re-used while perf events are active on the CPU. The put_cpu_id function
> will pend release of the ID until all perf cs_etm sessions are complete.
> 
> For backward compatibility the functions will attempt to use the same
> CPU IDs as the legacy system would have used if these are still available.
> 
> Non-cpu sources, such as the STM can use coresight_trace_id_get_system_id /
> coresight_trace_id_put_system_id.
> 
> Signed-off-by: Mike Leach <mike.leach@...aro.org>
> ---
>   drivers/hwtracing/coresight/Makefile          |   2 +-
>   .../hwtracing/coresight/coresight-trace-id.c  | 265 ++++++++++++++++++
>   .../hwtracing/coresight/coresight-trace-id.h  | 156 +++++++++++
>   include/linux/coresight-pmu.h                 |  10 +
>   4 files changed, 432 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/hwtracing/coresight/coresight-trace-id.c
>   create mode 100644 drivers/hwtracing/coresight/coresight-trace-id.h
> 
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index b6c4a48140ec..329a0c704b87 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -6,7 +6,7 @@ obj-$(CONFIG_CORESIGHT) += coresight.o
>   coresight-y := coresight-core.o  coresight-etm-perf.o coresight-platform.o \
>   		coresight-sysfs.o coresight-syscfg.o coresight-config.o \
>   		coresight-cfg-preload.o coresight-cfg-afdo.o \
> -		coresight-syscfg-configfs.o
> +		coresight-syscfg-configfs.o coresight-trace-id.o
>   obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o
>   coresight-tmc-y := coresight-tmc-core.o coresight-tmc-etf.o \
>   		      coresight-tmc-etr.o
> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.c b/drivers/hwtracing/coresight/coresight-trace-id.c
> new file mode 100644
> index 000000000000..9b85c376cb12
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-trace-id.c
> @@ -0,0 +1,265 @@
> +// SPDX-License-Identifier: GPL-2.0

...

> +int coresight_trace_id_read_cpu_id(int cpu)
> +{
> +	return _coresight_trace_id_read_cpu_id(cpu);
> +}
> +EXPORT_SYMBOL_GPL(coresight_trace_id_read_cpu_id);
> +
> +int coresight_trace_id_get_system_id(void)
> +{
> +	return coresight_trace_id_map_get_system_id(&id_map_default);
> +}
> +EXPORT_SYMBOL_GPL(coresight_trace_id_get_system_id);
> +
> +void coresight_trace_id_put_system_id(int id)
> +{
> +	coresight_trace_id_map_put_system_id(&id_map_default, id);
> +}
> +EXPORT_SYMBOL_GPL(coresight_trace_id_put_system_id);
> +
> +void coresight_trace_id_perf_start(void)
> +{
> +	atomic_inc(&perf_cs_etm_session_active);
> +}
> +EXPORT_SYMBOL_GPL(coresight_trace_id_perf_start);
> +
> +void coresight_trace_id_perf_stop(void)
> +{
> +	if (!atomic_dec_return(&perf_cs_etm_session_active))
> +		coresight_trace_id_release_all_pending();
> +}
> +EXPORT_SYMBOL_GPL(coresight_trace_id_perf_stop);
> +

This blank new line at the end of the file generates a checkpatch
warning for me. I have fixed it locally and applied it.

> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.h b/drivers/hwtracing/coresight/coresight-trace-id.h