Re: [PATCH v4 20/25] coresight: etm4x: Detect system instructions support

[Suzuki K Poulose]

On 11/24/20 12:41 AM, Tingwei Zhang wrote:
> On Mon, Nov 23, 2020 at 05:39:43PM +0800, Suzuki K Poulose wrote:
> > On 11/23/20 7:58 AM, Tingwei Zhang wrote:
> > > Hi Suzuki,
> > >
> > > On Fri, Nov 20, 2020 at 12:45:42AM +0800, Suzuki K Poulose wrote:
> > > > ETM v4.4 onwards adds support for system instruction access
> > > > to the ETM. Detect the support on an ETM and switch to using the
> > > > mode when available.
> > > >
> > > > Cc: Mike Leach <mike.leach@xxxxxxxxxx>
> > > > Reviewed-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> > > > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > > > ---
> > > >   .../coresight/coresight-etm4x-core.c          | 39 +++++++++++++++++++
> > > >   1 file changed, 39 insertions(+)
> > > >
> > > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> > > > b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> > > > index 7ac0a185c146..5cbea9c27f58 100644
> > > > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> > > > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> > > > @@ -684,6 +684,37 @@ static const struct coresight_ops etm4_cs_ops = {
> > > >   	.source_ops	= &etm4_source_ops,
> > > >   };
> > > >
> > > > +static inline bool cpu_supports_sysreg_trace(void)
> > > > +{
> > > > +	u64 dfr0 = read_sysreg_s(SYS_ID_AA64DFR0_EL1);
> > > > +
> > > > +	return ((dfr0 >> ID_AA64DFR0_TRACEVER_SHIFT) & 0xfUL) > 0;
> > > > +}
> > > > +
> > > > +static bool etm4_init_sysreg_access(struct etmv4_drvdata *drvdata,
> > > > +				    struct csdev_access *csa)
> > > > +{
> > > > +	u32 devarch;
> > > > +
> > > > +	if (!cpu_supports_sysreg_trace())
> > > > +		return false;
> > > > +
> > > > +	/*
> > > > +	 * ETMs implementing sysreg access must implement TRCDEVARCH.
> > > > +	 */
> > > > +	devarch = read_etm4x_sysreg_const_offset(TRCDEVARCH);
> > > > +	if ((devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETMv4x_ARCH)
> > >
> > > Is this driver suppose to work on ETM 5.0/ETE trace unit before ETE driver
> > > is ready?
> >
> > No, it is not supposed to work on an ETE without the ETE support. That check
> > ensures that we only detect ETMv4x for now. The ETE driver support adds the
> > ETE_ARCH as one of the supported ETMs. If you hack around it might still
> > probe,
> > but things could go terribly wrong if we access registers that are not
> > available
> > on ETE.
> >
> > Btw, are you able to test this series on an ETMv4.4+ system ?
> I'm trying to test this series on an ETE. Look like it's not correct.
> I'll apply ETE patch on top of this and test.

Yes please ! Much appreciated. Do you have a TRBE as well ? Or are you
using a legacy CoreSight topology ?

Kind regards
Suzuki