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

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Message-ID: <99a03fae-47fa-8f19-1768-4aeb28cac182@arm.com>
Date:   Tue, 17 Jan 2023 15:54:54 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Mike Leach <mike.leach@...aro.org>
Cc:     coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, 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

On 17/01/2023 13:02, Mike Leach wrote:
> On Mon, 16 Jan 2023 at 14:16, Suzuki K Poulose <suzuki.poulose@....com> wrote:
>>
>> 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.
>>
> OK, thanks.
> 
> The only thing I get out of checkpatch.pl for this patch (and indeed
> the entire set) is:
> 
> WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?

Ah, sorry. It is not the checkpatch, but git am complained. Sorry for 
the confusion.

Cheers
Suzuki