linux-kernel - Re: [PATCH V2 06/15] coresight: tmc: making prepare/unprepare functions generic

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Date:	Tue, 19 Apr 2016 09:22:27 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Suzuki K Poulose <Suzuki.Poulose@....com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 06/15] coresight: tmc: making prepare/unprepare
 functions generic

On 19 April 2016 at 06:30, Suzuki K Poulose <Suzuki.Poulose@....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@...aro.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.

>
> Irrespective of that,
>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
>