Re: [PATCH v5 3/3] coresight: dummy: Add static trace id support for dummy source

[Suzuki K Poulose <suzuki.poulose@xxxxxxx>]

On 21/10/2024 13:31, Suzuki K Poulose wrote:
> On 18/10/2024 04:22, Mao Jinlong wrote:
> > Some dummy source has static trace id configured in HW and it cannot
> > be changed via software programming. Configure the trace id in device
> > tree and reserve the id when device probe.
> >
> > Signed-off-by: Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
> > ---
> >   .../sysfs-bus-coresight-devices-dummy-source  | 15 +++++
> >   drivers/hwtracing/coresight/coresight-dummy.c | 59 +++++++++++++++++--
> >   2 files changed, 70 insertions(+), 4 deletions(-)
> >   create mode 100644 Documentation/ABI/testing/sysfs-bus-coresight- 
> > devices-dummy-source
> >
> > diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices- 
> > dummy-source b/Documentation/ABI/testing/sysfs-bus-coresight-devices- 
> > dummy-source
> > new file mode 100644
> > index 000000000000..c7d975e75d85
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-dummy-source
> > @@ -0,0 +1,15 @@
> > +What:        /sys/bus/coresight/devices/dummy_source<N>/enable_source
> > +Date:        Oct 2024
> > +KernelVersion:    6.13
> > +Contact:    Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
> > +Description:    (RW) Enable/disable tracing of dummy source. A sink 
> > should be activated
> > +        before enabling the source. The path of coresight components 
> > linking
> > +        the source to the sink is configured and managed 
> > automatically by the
> > +        coresight framework.
> > +
> > +What:        /sys/bus/coresight/devices/dummy_source<N>/traceid
> > +Date:        Oct 2024
> > +KernelVersion:    6.13
> > +Contact:    Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
> > +Description:    (R) Show the trace ID that will appear in the trace 
> > stream
> > +        coming from this trace entity.
> > diff --git a/drivers/hwtracing/coresight/coresight-dummy.c b/drivers/ 
> > hwtracing/coresight/coresight-dummy.c
> > index bb85fa663ffc..602a7e89e311 100644
> > --- a/drivers/hwtracing/coresight/coresight-dummy.c
> > +++ b/drivers/hwtracing/coresight/coresight-dummy.c
> > @@ -11,10 +11,12 @@
> >   #include <linux/pm_runtime.h>
> >   #include "coresight-priv.h"
> > +#include "coresight-trace-id.h"
> >   struct dummy_drvdata {
> >       struct device            *dev;
> >       struct coresight_device        *csdev;
> > +    u8                traceid;
> >   };
> >   DEFINE_CORESIGHT_DEVLIST(source_devs, "dummy_source");
> > @@ -72,6 +74,32 @@ static const struct coresight_ops dummy_sink_cs_ops 
> > = {
> >       .sink_ops = &dummy_sink_ops,
> >   };
> > +/* User can get the trace id of dummy source from this node. */
> > +static ssize_t traceid_show(struct device *dev,
> > +                struct device_attribute *attr, char *buf)
> > +{
> > +    unsigned long val;
> > +    struct dummy_drvdata *drvdata = dev_get_drvdata(dev->parent);
> > +
> > +    val = drvdata->traceid;
> > +    return scnprintf(buf, PAGE_SIZE, "%#lx\n", val);
> > +}
> > +static DEVICE_ATTR_RO(traceid);
> > +
> > +static struct attribute *coresight_dummy_attrs[] = {
> > +    &dev_attr_traceid.attr,
> > +    NULL,
> > +};
> > +
> > +static const struct attribute_group coresight_dummy_group = {
> > +    .attrs = coresight_dummy_attrs,
> > +};
> > +
> > +static const struct attribute_group *coresight_dummy_groups[] = {
> > +    &coresight_dummy_group,
> > +    NULL,
> > +};
> > +
> >   static int dummy_probe(struct platform_device *pdev)
> >   {
> >       struct device *dev = &pdev->dev;
> > @@ -79,6 +107,11 @@ static int dummy_probe(struct platform_device *pdev)
> >       struct coresight_platform_data *pdata;
> >       struct dummy_drvdata *drvdata;
> >       struct coresight_desc desc = { 0 };
> > +    int ret, trace_id;
> > +
> > +    drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> > +    if (!drvdata)
> > +        return -ENOMEM;
> >       if (of_device_is_compatible(node, "arm,coresight-dummy-source")) {
> > @@ -90,6 +123,25 @@ static int dummy_probe(struct platform_device *pdev)
> >           desc.subtype.source_subtype =
> >                       CORESIGHT_DEV_SUBTYPE_SOURCE_OTHERS;
> >           desc.ops = &dummy_source_cs_ops;
> > +        desc.groups = coresight_dummy_groups;
> > +
> > +        ret = coresight_get_static_trace_id(dev, &trace_id);
> > +        if (!ret) {
> > +            /* Get the static id if id is set in device tree. */
> > +            ret = coresight_trace_id_get_static_system_id(trace_id);

This may be worth an error message, it is a rare one. Othewise, there is
no clue on what caused the failure. Or have a specific error code as a
result ?

> > +            if (ret < 0)
> > +                return ret;

e.g., return -EBUSY ? /* Device or resource not available */

> > +
> > +        } else {
> > +            /* Get next available id if id is not set in device tree. */
> > +            trace_id = coresight_trace_id_get_system_id();
> > +            if (trace_id < 0) {
> > +                ret = trace_id;
> > +                return ret;
> > +            }
> > +        }
> > +        drvdata->traceid = (u8)trace_id;
> > +
> >       } else if (of_device_is_compatible(node, "arm,coresight-dummy- 
> > sink")) {
> >           desc.name = coresight_alloc_device_name(&sink_devs, dev);
> >           if (!desc.name)
> > @@ -108,10 +160,6 @@ static int dummy_probe(struct platform_device *pdev)
> >           return PTR_ERR(pdata);
> >       pdev->dev.platform_data = pdata;
> > -    drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> > -    if (!drvdata)
> > -        return -ENOMEM;
> > -
> >       drvdata->dev = &pdev->dev;
> >       platform_set_drvdata(pdev, drvdata);

Additionally we should drop the system_id if registering the coresight 
device fails.


Suzuki

> > @@ -131,7 +179,10 @@ static void dummy_remove(struct platform_device 
> > *pdev)
> >   {
> >       struct dummy_drvdata *drvdata = platform_get_drvdata(pdev);
> >       struct device *dev = &pdev->dev;
> > +    struct device_node *node = dev->of_node;
>
> ^^ Why is this needed ? The rest looks fine to me
>
> > +    if (IS_VALID_CS_TRACE_ID(drvdata->traceid))
> > +        coresight_trace_id_put_system_id(drvdata->traceid);
> >       pm_runtime_disable(dev);
> >       coresight_unregister(drvdata->csdev);
> >   }