Re: [PATCH v8 16/24] coresight: cti: add function to register cti associate ops

Mike Leach
2020-08-17T18:51:09Z

Hi Mathieu,

On Mon, 17 Aug 2020 at 17:02, Mathieu Poirier
<mathieu.poirier@linaro.org> wrote:
>
> On Fri, Aug 07, 2020 at 07:11:45PM +0800, Tingwei Zhang wrote:
> > Add static cti_assoc_ops to coresight core driver. Let cti
> > driver register the add_assoc and remove_assoc call back.
> > Avoid coresight core driver to depend on cti driver.
> >
> > Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
> > Tested-by: Mike Leach <mike.leach@linaro.org>
> > ---
> > drivers/hwtracing/coresight/coresight-cti.c | 32 ++++++++++++++++++--
> > drivers/hwtracing/coresight/coresight-priv.h | 14 ++++-----
> > drivers/hwtracing/coresight/coresight.c | 21 +++++++++++--
> > 3 files changed, 53 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
> > index 3ccc703dc940..1f470c47ba70 100644
> > --- a/drivers/hwtracing/coresight/coresight-cti.c
> > +++ b/drivers/hwtracing/coresight/coresight-cti.c
> > @@ -589,7 +589,6 @@ void cti_add_assoc_to_csdev(struct coresight_device *csdev)
> > cti_add_done:
> > mutex_unlock(&ect_mutex);
> > }
> > -EXPORT_SYMBOL_GPL(cti_add_assoc_to_csdev);
> >
> > /*
> > * Removing the associated devices is easier.
> > @@ -616,7 +615,15 @@ void cti_remove_assoc_from_csdev(struct coresight_device *csdev)
> > }
> > mutex_unlock(&ect_mutex);
> > }
> > -EXPORT_SYMBOL_GPL(cti_remove_assoc_from_csdev);
>
> Mike and Tingwei,
>
> It seems to me that functions cti_add_assoc_to_csdev() and
> cti_remote_assoc_from_csdev() don't have to be exported. They could be called
> in cti_probe() and cti_device_release() with the ect_mutex held, the same way
> cti_update_conn_xrefs() and cti_remove_conn_xrefs() are.
>

The different functions handle two different initialisation & two
different teardown ordering scenarios
a) csdev - e.g. ETM is discovered & initialised before the associated
CTI. Therefore the CTI has to establish interconnections on creation -
calls cti_update_conn_xrefs() .
b) CTI is discovered before csdev - therefore the csdev calls
cti_add_assoc_to_csdev().
c) csdev is torn down before CTI - therefore csdev calls
cti_remove_assoc_from_csdev()
d) CTI is torn down before csdev - therefore calls cti_remove_conn_xrefs()

We can't call cti_add_assoc_to_csdev() in cti probe as the csdev does
not exist yet. Bear in mind that one CTI can actually be associated
with multiple different csdev devices - especially in the none CPU
bound infrastructure such as funnels and sinks.
This has always been the case since the first CTI set - but is even
more important now the modules can be removed / added as required.

Regards

Mike

> If my assessment is correct this patch would be simpler.
>
> Thanks,
> Mathieu
>
>
> > +
> > +/*
> > + * Operations to add and remove associated CTI.
> > + * Register to coresight core driver as call back function.
> > + */
> > +static struct cti_assoc_op cti_assoc_ops = {
> > + .add = cti_add_assoc_to_csdev,
> > + .remove = cti_remove_assoc_from_csdev
> > +};
> >
> > /*
> > * Update the cross references where the associated device was found
> > @@ -972,4 +979,23 @@ static struct amba_driver cti_driver = {
> > .probe = cti_probe,
> > .id_table = cti_ids,
> > };
> > -builtin_amba_driver(cti_driver);
> > +
> > +static int __init cti_init(void)
> > +{
> > + int ret;
> > +
> > + ret = amba_driver_register(&cti_driver);
> > + if (ret)
> > + pr_info("Error registering cti driver\n");
> > + coresight_set_cti_ops(&cti_assoc_ops);
> > + return ret;
> > +}
> > +
> > +static void __exit cti_exit(void)
> > +{
> > + coresight_remove_cti_ops();
> > + amba_driver_unregister(&cti_driver);
> > +}
> > +
> > +module_init(cti_init);
> > +module_exit(cti_exit);
> > diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> > index dcb8aeb6af62..6cde6cf42554 100644
> > --- a/drivers/hwtracing/coresight/coresight-priv.h
> > +++ b/drivers/hwtracing/coresight/coresight-priv.h
> > @@ -173,15 +173,13 @@ static inline int etm_readl_cp14(u32 off, unsigned int *val) { return 0; }
> > static inline int etm_writel_cp14(u32 off, u32 val) { return 0; }
> > #endif
> >
> > -#ifdef CONFIG_CORESIGHT_CTI
> > -extern void cti_add_assoc_to_csdev(struct coresight_device *csdev);
> > -extern void cti_remove_assoc_from_csdev(struct coresight_device *csdev);
> > +struct cti_assoc_op {
> > + void (*add)(struct coresight_device *csdev);
> > + void (*remove)(struct coresight_device *csdev);
> > +};
> >
> > -#else
> > -static inline void cti_add_assoc_to_csdev(struct coresight_device *csdev) {}
> > -static inline void
> > -cti_remove_assoc_from_csdev(struct coresight_device *csdev) {}
> > -#endif
> > +extern void coresight_set_cti_ops(const struct cti_assoc_op *cti_op);
> > +extern void coresight_remove_cti_ops(void);
> >
> > /*
> > * Macros and inline functions to handle CoreSight UCI data and driver
> > diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
> > index 0b0e31577b9b..31b9ec8d3b9c 100644
> > --- a/drivers/hwtracing/coresight/coresight.c
> > +++ b/drivers/hwtracing/coresight/coresight.c
> > @@ -57,6 +57,20 @@ const u32 coresight_barrier_pkt[4] = {
> > 0x7fffffff, 0x7fffffff, 0x7fffffff, 0x7fffffff};
> > EXPORT_SYMBOL_GPL(coresight_barrier_pkt);
> >
> > +static const struct cti_assoc_op *cti_assoc_ops;
> > +
> > +void coresight_set_cti_ops(const struct cti_assoc_op *cti_op)
> > +{
> > + cti_assoc_ops = cti_op;
> > +}
> > +EXPORT_SYMBOL_GPL(coresight_set_cti_ops);
> > +
> > +void coresight_remove_cti_ops(void)
> > +{
> > + cti_assoc_ops = NULL;
> > +}
> > +EXPORT_SYMBOL_GPL(coresight_remove_cti_ops);
> > +
> > static int coresight_id_match(struct device *dev, void *data)
> > {
> > int trace_id, i_trace_id;
> > @@ -1242,7 +1256,8 @@ static void coresight_device_release(struct device *dev)
> > {
> > struct coresight_device *csdev = to_coresight_device(dev);
> >
> > - cti_remove_assoc_from_csdev(csdev);
> > + if (cti_assoc_ops && cti_assoc_ops->remove)
> > + cti_assoc_ops->remove(csdev);
> > fwnode_handle_put(csdev->dev.fwnode);
> > kfree(csdev->refcnt);
> > kfree(csdev);
> > @@ -1553,8 +1568,8 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
> > ret = coresight_fixup_device_conns(csdev);
> > if (!ret)
> > ret = coresight_fixup_orphan_conns(csdev);
> > - if (!ret)
> > - cti_add_assoc_to_csdev(csdev);
> > + if (!ret && cti_assoc_ops && cti_assoc_ops->add)
> > + cti_assoc_ops->add(csdev);
> >
> > mutex_unlock(&coresight_mutex);
> > if (ret) {
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > a Linux Foundation Collaborative Project
> >

--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK