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SubjectRe: [PATCH V2 06/15] coresight: tmc: making prepare/unprepare functions generic
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On 19/04/16 16:22, Mathieu Poirier wrote:
> On 19 April 2016 at 06:30, Suzuki K Poulose <Suzuki.Poulose@arm.com> wrote:
>> On 12/04/16 18:54, Mathieu Poirier wrote:
>>>
>>> Dealing with HW related matters in tmc_read_prepare/unprepare
>>> becomes convoluted when many cases need to be handled distinctively.
>>>
>>> As such moving processing related to HW setup to individual driver
>>> files and keep the core driver generic.
>>>
>>> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
>>> ---
>>> drivers/hwtracing/coresight/coresight-tmc-etf.c | 62
>>> ++++++++++++++++++++++++-
>>> drivers/hwtracing/coresight/coresight-tmc-etr.c | 42 ++++++++++++++++-
>>> drivers/hwtracing/coresight/coresight-tmc.c | 55
>>> +++++-----------------
>>> drivers/hwtracing/coresight/coresight-tmc.h | 8 ++--
>>> 4 files changed, 117 insertions(+), 50 deletions(-)
>>>
>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c
>>> b/drivers/hwtracing/coresight/coresight-tmc-etr.c
>>> index 910d6f3b7d26..495540e9064d 100644
>>> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
>>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
>>> @@ -70,7 +70,7 @@ static void tmc_etr_dump_hw(struct tmc_drvdata *drvdata)
>>> drvdata->buf = drvdata->vaddr;
>>> }
>>>
>>> -void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
>>> +static void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
>>> {
>>> CS_UNLOCK(drvdata->base);
>>>
>>> @@ -126,3 +126,43 @@ static const struct coresight_ops_sink
>>> tmc_etr_sink_ops = {
>>> const struct coresight_ops tmc_etr_cs_ops = {
>>> .sink_ops = &tmc_etr_sink_ops,
>>> };
>>> +
>>> +int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
>>> +{
>>> + unsigned long flags;
>>> +
>>> + /* config types are set a boot time and never change */
>>> + if (drvdata->config_type != TMC_CONFIG_TYPE_ETR)
>>> + return -EINVAL;
>>
>>
>> ...
>>
>>> +
>>> +int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata)
>>> +{
>>> + unsigned long flags;
>>> +
>>> + /* config types are set a boot time and never change */
>>> + if (drvdata->config_type != TMC_CONFIG_TYPE_ETR)
>>> + return -EINVAL;
>>> +
>>
>>
>> For both cases above should we WARN_ON_ONCE() if we encounter such a case ?
>
> WARN_ON_ONCE() would also be valid, albeit very blunt. Those
> functions are user space triggered and returning -EINVAL will stop
> everything - the end result is the same. I suppose that on such
> condition fighting back with a backtrace will force people to pay
> attention or report the problem.

We do necessary checks to route the caller here, so we shouldn't really
hit the condition with the tmc_read_prepare(). So WARN_ON_ONCE() might be a
good check to make sure we don't hit it from say, perf driver or something
really went bad under the hood (corrupted ?). I am not too particular about it.

Suzuki

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