Re: [PATCH v2 8/9] coresight: Enable and disable helper devices adjacent to the path

[Suzuki K Poulose]

On 29/03/2023 13:04, James Clark wrote:
> On 17/03/2023 11:04, Suzuki K Poulose wrote:
> > On 10/03/2023 16:06, James Clark wrote:
> > > Currently CATU is the only helper device, and its enable and disable
> > > calls are hard coded. To allow more helper devices to be added in a
> > > generic way, remove these hard coded calls and just enable and disable
> > > all helper devices.
> > >
> > > This has to apply to helpers adjacent to the path, because they will
> > > never be in the path. CATU was already discovered in this way, so
> > > there is no change there.
> > >
> > > One change that is needed is for CATU to call back into ETR to allocate
> > > the buffer. Because the enable call was previously hard coded, it was
> > > done at a point where the buffer was already allocated, but this is no
> > > longer the case.
> > >
> > > Signed-off-by: James Clark <james.clark@xxxxxxx>
> > > ---
> > >    drivers/hwtracing/coresight/coresight-catu.c  | 34 ++++++++--
> > >    drivers/hwtracing/coresight/coresight-core.c  | 68 ++++++++++++++++++-
> > >    .../hwtracing/coresight/coresight-tmc-etr.c   | 28 --------
> > >    include/linux/coresight.h                     |  3 +-
> > >    4 files changed, 99 insertions(+), 34 deletions(-)
> > >
> > > diff --git a/drivers/hwtracing/coresight/coresight-catu.c
> > > b/drivers/hwtracing/coresight/coresight-catu.c
> > > index bc90a03f478f..24a08a2b96b1 100644
> > > --- a/drivers/hwtracing/coresight/coresight-catu.c
> > > +++ b/drivers/hwtracing/coresight/coresight-catu.c
> > > @@ -395,13 +395,32 @@ static inline int catu_wait_for_ready(struct
> > > catu_drvdata *drvdata)
> > >        return coresight_timeout(csa, CATU_STATUS, CATU_STATUS_READY, 1);
> > >    }
> > >    -static int catu_enable_hw(struct catu_drvdata *drvdata, void *data)
> > > +static struct coresight_device *
> > > +catu_get_etr_device(struct coresight_device *csdev)
> > > +{
> > > +    int i;
> > > +    struct coresight_device *tmp;
> > > +
> > > +    for (i = 0; i < csdev->pdata->nr_inconns; i++) {
> > > +        tmp = csdev->pdata->in_conns[i].remote_dev;
> > > +        if (tmp && tmp->type == CORESIGHT_DEV_TYPE_SINK &&
> > > +            tmp->subtype.sink_subtype ==
> > > +                CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM)
> > > +            return tmp;
> > > +    }
> > > +
> > > +    return NULL;
> > > +}
> > > +
> > > +static int catu_enable_hw(struct catu_drvdata *drvdata, enum cs_mode
> > > cs_mode,
> > > +              void *data)
> > >    {
> > >        int rc;
> > >        u32 control, mode;
> > > -    struct etr_buf *etr_buf = data;
> > > +    struct etr_buf *etr_buf = NULL;
> > >        struct device *dev = &drvdata->csdev->dev;
> > >        struct coresight_device *csdev = drvdata->csdev;
> > > +    struct coresight_device *etrdev;
> > >          if (catu_wait_for_ready(drvdata))
> > >            dev_warn(dev, "Timeout while waiting for READY\n");
> > > @@ -416,6 +435,12 @@ static int catu_enable_hw(struct catu_drvdata
> > > *drvdata, void *data)
> > >        if (rc)
> > >            return rc;
> > >    +    etrdev = catu_get_etr_device(csdev);
> > > +    if (etrdev) {
> > > +        etr_buf = tmc_etr_get_buffer(etrdev, cs_mode, data);
> > > +        if (IS_ERR(etr_buf))
> > > +            return PTR_ERR(etr_buf);
> > > +    }
> >
> > WARN_ON(!etrdev) ? We are not supposed to reach in the first place and
> > return.
>
> I saw there was the pass-through mode below which I thought didn't need
> an ETR device. I think I followed the code through and there was a way
> for it to get there without an ETR in the existing version, but now I'm
> not sure.


> Or does it still need the ETR device but it just doesn't
> access the buffer?

The first part is correct. Without an ETR, CATU wouldn't be a helper
device, and wouldn't get here in "enable CATU" via the helper route.
The CATU chooses the mode depending on the etr_buf mode.


Suzuki