Re: [PATCH v2 1/7] coresight: etm-perf: Clarify comment on perf options

[Leo Yan]

Hi Suzuki,

On Tue, Feb 02, 2021 at 11:00:42PM +0000, Suzuki Kuruppassery Poulose wrote:
> Hi Leo
> 
> On 2/2/21 4:38 PM, Leo Yan wrote:
> > In theory, the options should be arbitrary values and are neutral for
> > any ETM version; so far perf tool uses ETMv3.5/PTM ETMCR config bits
> > except for register's bit definitions, also uses as options.
> > 
> > This can introduce confusion, especially if we want to add a new option
> > but the new option is not supported by ETMv3.5/PTM ETMCR.  But on the
> > other hand, we cannot change options since these options are generic
> > CoreSight PMU ABI.
> > 
> > For easier maintenance and avoid confusion, this patch refines the
> > comment to clarify perf options, and gives out the background info for
> > these bits are coming from ETMv3.5/PTM.  Afterwards, we should take
> > these options as general knobs, and if there have any confliction with
> > ETMv3.5/PTM, should consider to define saperate macros for ETMv3.5/PTM
> > ETMCR config bits.
> > 
> > Suggested-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> 
> The patch looks good to me.  The only concern I have is, whether
> we should split this patch to kernel vs tools ? As the kernel
> changes go via coresight tree and the tools patch may go via
> perf tree ?

Yes, will split the patch.

> Either way, for the patch:
> 
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>

Thanks for review and suggestion.

> > ---
> >   .../hwtracing/coresight/coresight-etm-perf.c    |  5 ++++-
> >   include/linux/coresight-pmu.h                   | 17 ++++++++++++-----
> >   tools/include/linux/coresight-pmu.h             | 17 ++++++++++++-----
> >   3 files changed, 28 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> > index bdc34ca449f7..465ef1aa8c82 100644
> > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> > @@ -27,7 +27,10 @@ static bool etm_perf_up;
> >   static DEFINE_PER_CPU(struct perf_output_handle, ctx_handle);
> >   static DEFINE_PER_CPU(struct coresight_device *, csdev_src);
> > -/* ETMv3.5/PTM's ETMCR is 'config' */
> > +/*
> > + * The PMU formats were orignally for ETMv3.5/PTM's ETMCR 'config';
> > + * now take them as general formats and apply on all ETMs.
> > + */
> >   PMU_FORMAT_ATTR(cycacc,		"config:" __stringify(ETM_OPT_CYCACC));
> >   PMU_FORMAT_ATTR(contextid,	"config:" __stringify(ETM_OPT_CTXTID));
> >   PMU_FORMAT_ATTR(timestamp,	"config:" __stringify(ETM_OPT_TS));
> > diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h
> > index b0e35eec6499..5dc47cfdcf07 100644
> > --- a/include/linux/coresight-pmu.h
> > +++ b/include/linux/coresight-pmu.h
> > @@ -10,11 +10,18 @@
> >   #define CORESIGHT_ETM_PMU_NAME "cs_etm"
> >   #define CORESIGHT_ETM_PMU_SEED  0x10
> > -/* ETMv3.5/PTM's ETMCR config bit */
> > -#define ETM_OPT_CYCACC  12
> > -#define ETM_OPT_CTXTID	14
> > -#define ETM_OPT_TS      28
> > -#define ETM_OPT_RETSTK	29
> > +/*
> > + * Below are the definition of bit offsets for perf option, and works as
> > + * arbitrary values for all ETM versions.
> > + *
> > + * Most of them are orignally from ETMv3.5/PTM's ETMCR config, therefore,
> > + * ETMv3.5/PTM doesn't define ETMCR config bits with prefix "ETM3_" and
> > + * directly use below macros as config bits.
> > + */
> > +#define ETM_OPT_CYCACC		12
> > +#define ETM_OPT_CTXTID		14
> > +#define ETM_OPT_TS		28
> > +#define ETM_OPT_RETSTK		29
> >   /* ETMv4 CONFIGR programming bits for the ETM OPTs */
> >   #define ETM4_CFG_BIT_CYCACC	4
> > diff --git a/tools/include/linux/coresight-pmu.h b/tools/include/linux/coresight-pmu.h
> > index b0e35eec6499..5dc47cfdcf07 100644
> > --- a/tools/include/linux/coresight-pmu.h
> > +++ b/tools/include/linux/coresight-pmu.h
> > @@ -10,11 +10,18 @@
> >   #define CORESIGHT_ETM_PMU_NAME "cs_etm"
> >   #define CORESIGHT_ETM_PMU_SEED  0x10
> > -/* ETMv3.5/PTM's ETMCR config bit */
> > -#define ETM_OPT_CYCACC  12
> > -#define ETM_OPT_CTXTID	14
> > -#define ETM_OPT_TS      28
> > -#define ETM_OPT_RETSTK	29
> > +/*
> > + * Below are the definition of bit offsets for perf option, and works as
> > + * arbitrary values for all ETM versions.
> > + *
> > + * Most of them are orignally from ETMv3.5/PTM's ETMCR config, therefore,
> > + * ETMv3.5/PTM doesn't define ETMCR config bits with prefix "ETM3_" and
> > + * directly use below macros as config bits.
> > + */
> > +#define ETM_OPT_CYCACC		12
> > +#define ETM_OPT_CTXTID		14
> > +#define ETM_OPT_TS		28
> > +#define ETM_OPT_RETSTK		29
> >   /* ETMv4 CONFIGR programming bits for the ETM OPTs */
> >   #define ETM4_CFG_BIT_CYCACC	4
> > 
>