Re: [RFC PATCH 04/14] coresight: etm4x: Free up argument of etm4_init_arch_data

[Suzuki K Poulose]

On 07/30/2020 06:31 PM, Mathieu Poirier wrote:
> On Wed, Jul 22, 2020 at 06:20:30PM +0100, Suzuki K Poulose wrote:
> > etm4_init_arch_data is called early during the device probe,
> > even before the coresight_device is registered. Since we are
> > about to replace the direct access via abstraction layer, we
> > need a way to pass in the csdev_access for the given device.
> > Towards this free up the argument, which is already available
> > via etmdrvdata[smp_processor_id()].
> >
> > Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> > Cc: Mike Leach <mike.leach@xxxxxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---
> >   drivers/hwtracing/coresight/coresight-etm4x.c | 15 +++++++++++----
> >   1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> > index 7bb74c659c4f..67deb4a4e618 100644
> > --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> > +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> > @@ -614,7 +614,8 @@ static const struct coresight_ops etm4_cs_ops = {
> >   	.source_ops	= &etm4_source_ops,
> >   };
> >   
> > -static void etm4_init_arch_data(void *info)
> > +
> > +static void etm4_init_arch_data(void *__unused)
> >   {
> >   	u32 etmidr0;
> >   	u32 etmidr1;
> > @@ -622,8 +623,14 @@ static void etm4_init_arch_data(void *info)
> >   	u32 etmidr3;
> >   	u32 etmidr4;
> >   	u32 etmidr5;
> > -	struct etmv4_drvdata *drvdata = info;
> > -	int i;
> > +	struct etmv4_drvdata *drvdata;
> > +	int i, cpu;
> > +
> > +	cpu = raw_smp_processor_id();
>
> Can you provide details on the motivation to use the raw_ version over the regular
> one?  As far as I can see in linux/smp.h there is no difference between them
> unless DEBUB_PREEMPT is enabled.  Even then the debug version won't complain
> since the task is CPU affined.

Right, it is partly my misunderstanding. debug_smp_processor_id() is to
detect cases where smp_processor_id() is called in pre-emptible
contexts. This is not the case here. So it is fine to use the
smp_processor_id(). I will switch to that in the next version.

Thanks
Suzuki