On 22/04/2023 08:37, Hao Zhang wrote:

Some Coresight devices that kernel don't have permission to access or configure. So there need driver to register dummy devices as Coresight devices. It may also be used to define components that may not have any programming interfaces (e.g, static links), so that paths can be established in the driver. 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@quicinc.com

drivers/hwtracing/coresight/Kconfig | 11 ++ drivers/hwtracing/coresight/Makefile | 1 + drivers/hwtracing/coresight/coresight-dummy.c | 179 ++++++++++++++++++ include/linux/coresight.h | 1 + 4 files changed, 192 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..1fb8b3d1c170 --- /dev/null +++ b/drivers/hwtracing/coresight/coresight-dummy.c @@ -0,0 +1,179 @@ +// 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(source_devs, "dummy_source"); +DEFINE_CORESIGHT_DEVLIST(sink_devs, "dummy_sink");

+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_dbg(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_dbg(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_dbg(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_dbg(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 dummy_source_cs_ops = {

• .source_ops = &dummy_source_ops,

+};

+static const struct coresight_ops_sink dummy_sink_ops = {

• .enable = dummy_sink_enable,
• .disable = dummy_sink_disable,

+};

+static const struct coresight_ops dummy_sink_cs_ops = {

• .sink_ops = &dummy_sink_ops,

+};

+static int dummy_probe(struct platform_device *pdev) +{

• int trace_id;
• struct device *dev = &pdev->dev;
• struct device_node *node = dev->of_node;
• struct coresight_platform_data *pdata;
• struct dummy_drvdata *drvdata;
• struct coresight_desc desc = { 0 };
• if (of_device_is_compatible(node, "arm,coresight-dummy-source")) {

• trace_id = coresight_trace_id_get_system_id();
  

Why is this needed ? If at all we need something, this must be explicitly asked for. How is this used ?

• if (trace_id < 0)
  

• 	return trace_id;
  

• desc.name = coresight_alloc_device_name(&source_devs, dev);
  

• if (!desc.name)
  

• 	return -ENOMEM;
  

• desc.type = CORESIGHT_DEV_TYPE_SOURCE;
  

• desc.subtype.source_subtype =
  

• 			CORESIGHT_DEV_SUBTYPE_SOURCE_OTHERS;
  

• desc.ops = &dummy_source_cs_ops;
  

• } else if (of_device_is_compatible(node, "arm,coresight-dummy-sink")) {

• desc.name = coresight_alloc_device_name(&sink_devs, dev);
  

• if (!desc.name)
  

• 	return -ENOMEM;
  

• desc.type = CORESIGHT_DEV_TYPE_SINK;
  

• desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_DUMMY;
  

• desc.ops = &dummy_sink_cs_ops;
  

• } else {

• dev_err(dev, "Device type not set\n");
  

• return -EINVAL;
  

• }
• 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;
  

If we have allocated a traceid, we must clean it up here and/or at device removal.

• drvdata->dev = &pdev->dev;
• platform_set_drvdata(pdev, drvdata);
• 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);
  

• drvdata->traceid = (u8)trace_id;

Where/how is this used ?

Suzuki