Re: [PATCH v2 1/3] Coresight: Add coresight dummy driver

[Hao Zhang <quic_hazha@xxxxxxxxxxx>]

Hi Mike,

On 3/27/2023 11:58 PM, Mike Leach wrote:
> Hi,
>
> On Fri, 24 Mar 2023 at 06:16, Hao Zhang <quic_hazha@xxxxxxxxxxx> wrote:
> > Some Coresight devices that HLOS don't have permission to access
> > or configure. Such as Coresight sink EUD, some TPDMs etc. So there
> > need driver to register dummy devices as Coresight devices. Provide
> > Coresight API for dummy device operations, such as enabling and
> > disabling dummy devices. Build the Coresight path for dummy sink or
> > dummy source for debugging.
> >
> > Signed-off-by: Hao Zhang <quic_hazha@xxxxxxxxxxx>
> > ---
> >   drivers/hwtracing/coresight/Kconfig           |  11 ++
> >   drivers/hwtracing/coresight/Makefile          |   1 +
> >   drivers/hwtracing/coresight/coresight-dummy.c | 176 ++++++++++++++++++
> >   3 files changed, 188 insertions(+)
> >   create mode 100644 drivers/hwtracing/coresight/coresight-dummy.c
> >
> > diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
> > index 2b5bbfffbc4f..06f0a7594169 100644
> > --- a/drivers/hwtracing/coresight/Kconfig
> > +++ b/drivers/hwtracing/coresight/Kconfig
> > @@ -236,4 +236,15 @@ config CORESIGHT_TPDA
> >
> >            To compile this driver as a module, choose M here: the module will be
> >            called coresight-tpda.
> > +
> > +config CORESIGHT_DUMMY
> > +       tristate "Dummy driver support"
> > +       help
> > +         Enables support for dummy driver. Dummy driver can be used for
> > +         CoreSight sources/sinks that are owned and configured by some
> > +         other subsystem and use Linux drivers to configure rest of trace
> > +         path.
> > +
> > +         To compile this driver as a module, choose M here: the module will be
> > +         called coresight-dummy.
> >   endif
> > diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> > index 33bcc3f7b8ae..995d3b2c76df 100644
> > --- a/drivers/hwtracing/coresight/Makefile
> > +++ b/drivers/hwtracing/coresight/Makefile
> > @@ -30,3 +30,4 @@ obj-$(CONFIG_CORESIGHT_TPDA) += coresight-tpda.o
> >   coresight-cti-y := coresight-cti-core.o        coresight-cti-platform.o \
> >                     coresight-cti-sysfs.o
> >   obj-$(CONFIG_ULTRASOC_SMB) += ultrasoc-smb.o
> > +obj-$(CONFIG_CORESIGHT_DUMMY) += coresight-dummy.o
> > diff --git a/drivers/hwtracing/coresight/coresight-dummy.c b/drivers/hwtracing/coresight/coresight-dummy.c
> > new file mode 100644
> > index 000000000000..2d4eb3e546eb
> > --- /dev/null
> > +++ b/drivers/hwtracing/coresight/coresight-dummy.c
> > @@ -0,0 +1,176 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved.
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/coresight.h>
> > +#include <linux/of.h>
> > +#include <linux/pm_runtime.h>
> > +
> > +#include "coresight-priv.h"
> > +#include "coresight-trace-id.h"
> > +
> > +struct dummy_drvdata {
> > +       struct device                   *dev;
> > +       struct coresight_device         *csdev;
> > +       int                             traceid;
> > +};
> > +
> > +DEFINE_CORESIGHT_DEVLIST(dummy_devs, "dummy");
> > +
> > +static int dummy_source_enable(struct coresight_device *csdev,
> > +                              struct perf_event *event, u32 mode)
> > +{
> > +       struct dummy_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> > +
> > +       dev_info(drvdata->dev, "Dummy source enabled\n");
> > +
> > +       return 0;
> > +}
> > +
> > +static void dummy_source_disable(struct coresight_device *csdev,
> > +                                struct perf_event *event)
> > +{
> > +       struct dummy_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> > +
> > +       dev_info(drvdata->dev, "Dummy source disabled\n");
> > +}
> > +
> > +static int dummy_sink_enable(struct coresight_device *csdev, u32 mode,
> > +                               void *data)
> > +{
> > +       struct dummy_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> > +
> > +       dev_info(drvdata->dev, "Dummy sink enabled\n");
> > +
> > +       return 0;
> > +}
> > +
> > +static int dummy_sink_disable(struct coresight_device *csdev)
> > +{
> > +       struct dummy_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> > +
> > +       dev_info(drvdata->dev, "Dummy sink disabled\n");
> > +
> > +       return 0;
> > +}
> > +
> > +static const struct coresight_ops_source dummy_source_ops = {
> > +       .enable         = dummy_source_enable,
> > +       .disable        = dummy_source_disable,
> > +};
> > +
> > +static const struct coresight_ops_sink dummy_sink_ops = {
> > +       .enable         = dummy_sink_enable,
> > +       .disable        = dummy_sink_disable,
> > +};
> > +
> > +static const struct coresight_ops dummy_cs_ops = {
> > +       .source_ops     = &dummy_source_ops,
> > +       .sink_ops       = &dummy_sink_ops,
> > +};
> > +
> > +static int dummy_probe(struct platform_device *pdev)
> > +{
> > +       int ret, trace_id;
> > +       struct device *dev = &pdev->dev;
> > +       struct coresight_platform_data *pdata;
> > +       struct dummy_drvdata *drvdata;
> > +       struct coresight_desc desc = { 0 };
> > +
> > +       desc.name = coresight_alloc_device_name(&dummy_devs, dev);
> > +       if (!desc.name)
> > +               return -ENOMEM;
> > +
> > +       pdata = coresight_get_platform_data(dev);
> > +       if (IS_ERR(pdata))
> > +               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);
> > +
> > +       if (of_property_read_bool(pdev->dev.of_node, "qcom,dummy-source")) {
> > +               desc.type = CORESIGHT_DEV_TYPE_SOURCE;
> > +               desc.subtype.source_subtype =
> > +                                       CORESIGHT_DEV_SUBTYPE_SOURCE_OTHERS;
> > +       } else if (of_property_read_bool(pdev->dev.of_node,
> > +                                        "qcom,dummy-sink")) {
> > +               desc.type = CORESIGHT_DEV_TYPE_SINK;
> > +               desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
>
> This will break the automatic sink selection on a system where perf is
> looking for a default sink and the dummy sink is closest  / first
> discovered.
>
> i.e. when perf record -e cs_etm// <options>
> is used to trace a program in linux, a dummy sink appearing in the
> coresight tree with this designation may be selected.
>
> This needs to be corrected, probably with a unique sub-type that
> appears before the CORESIGHT_DEV_SUBTYPE_SINK_BUFFER value in the enum
> as the selection is based on >= CORESIGHT_DEV_SUBTYPE_SINK_BUFFER.
>
> By implication adding a new value - will possibly affect other code
> using the enum values so will need to be checked
>
> Regards
>
> Mike

Thanks for your comments, I will add a new sub-type for dummy sink and 
check the impact of it.

Thanks,
Hao

> > +       } else {
> > +               dev_info(dev, "Device type not set\n");
> > +               return -EINVAL;
> > +       }
> > +
> > +       desc.ops = &dummy_cs_ops;
> > +       desc.pdata = pdev->dev.platform_data;
> > +       desc.dev = &pdev->dev;
> > +       drvdata->csdev = coresight_register(&desc);
> > +       if (IS_ERR(drvdata->csdev))
> > +               return PTR_ERR(drvdata->csdev);
> > +
> > +       trace_id = coresight_trace_id_get_system_id();
> > +       if (trace_id < 0) {
> > +               ret = trace_id;
> > +               goto cs_unregister;
> > +       }
> > +       drvdata->traceid = (u8)trace_id;
> > +
> > +       pm_runtime_enable(dev);
> > +       dev_info(dev, "Dummy device initialized\n");
> > +
> > +       return 0;
> > +
> > +cs_unregister:
> > +       coresight_unregister(drvdata->csdev);
> > +
> > +       return ret;
> > +}
> > +
> > +static int dummy_remove(struct platform_device *pdev)
> > +{
> > +       struct dummy_drvdata *drvdata = platform_get_drvdata(pdev);
> > +       struct device *dev = &pdev->dev;
> > +
> > +       coresight_trace_id_put_system_id(drvdata->traceid);
> > +       pm_runtime_disable(dev);
> > +       coresight_unregister(drvdata->csdev);
> > +       return 0;
> > +}
> > +
> > +static const struct of_device_id dummy_match[] = {
> > +       {.compatible = "qcom,coresight-dummy"},
> > +       {},
> > +};
> > +
> > +static struct platform_driver dummy_driver = {
> > +       .probe  = dummy_probe,
> > +       .remove = dummy_remove,
> > +       .driver = {
> > +               .name   = "coresight-dummy",
> > +               .of_match_table = dummy_match,
> > +       },
> > +};
> > +
> > +static int __init dummy_init(void)
> > +{
> > +       return platform_driver_register(&dummy_driver);
> > +}
> > +module_init(dummy_init);
> > +
> > +static void __exit dummy_exit(void)
> > +{
> > +       platform_driver_unregister(&dummy_driver);
> > +}
> > +module_exit(dummy_exit);
> > +
> > +MODULE_LICENSE("GPL");
> > +MODULE_DESCRIPTION("CoreSight dummy source driver");
> > --
> > 2.17.1