linux-kernel - Re: [PATCH v5 01/14] coresight: trace-id: Add API to dynamically assign Trace ID values

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Message-ID: <73d7a338-08f8-73e7-fab0-99dd36de92e7@arm.com>
Date:   Tue, 8 Nov 2022 19:14:27 +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 v5 01/14] coresight: trace-id: Add API to dynamically
 assign Trace ID values

On 01/11/2022 16:30, 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 +-
>   drivers/hwtracing/coresight/coresight-core.c  |   4 +
>   .../hwtracing/coresight/coresight-trace-id.c  | 225 ++++++++++++++++++
>   .../hwtracing/coresight/coresight-trace-id.h  | 154 ++++++++++++
>   include/linux/coresight-pmu.h                 |  10 +
>   5 files changed, 394 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/coresight-trace-id.h b/drivers/hwtracing/coresight/coresight-trace-id.h
> new file mode 100644
> index 000000000000..1d27977346b3
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-trace-id.h

> +/* check an ID is in the valid range */
> +#define IS_VALID_ID(id)	\
> +	((id > CORESIGHT_TRACE_ID_RES_0) && (id < CORESIGHT_TRACE_ID_RES_TOP))

Please could we make this more explicit as it is also used
by code outside the trace-id.c ? i.e, IS_VALID_TRACEID() ?
This stood out, while looking at the users of this helper.

Suzuki