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Message-ID: <883c72a4-0c72-fd08-1b04-577037138b43@arm.com>
Date: Tue, 28 Mar 2023 09:35:55 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Hao Zhang <quic_hazha@...cinc.com>,
Mike Leach <mike.leach@...aro.org>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Konrad Dybcio <konradybcio@...il.com>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Andy Gross <agross@...nel.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Jonathan Corbet <corbet@....net>, Leo Yan <leo.yan@...aro.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
Tingwei Zhang <quic_tingweiz@...cinc.com>,
Jinlong Mao <quic_jinlmao@...cinc.com>,
Yuanfang Zhang <quic_yuanfang@...cinc.com>,
Tao Zhang <quic_taozha@...cinc.com>,
Trilok Soni <quic_tsoni@...cinc.com>,
linux-arm-msm@...r.kernel.org,
Bjorn Andersson <andersson@...nel.org>,
linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 1/3] Coresight: Add coresight dummy driver
On 28/03/2023 08:22, Hao Zhang wrote:
> 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@...cinc.com> 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@...cinc.com>
>>> ---
>>> 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.
>>
Good point Mike.
>> 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.
Please keep this as the lowest priority, something like:
enum coresight_dev_subtype_sink {
+ CORESIGHT_DEV_SUBTYPE_SINK_DUMMY,
CORESIGHT_DEV_SUBTYPE_SINK_PORT,
CORESIGHT_DEV_SUBTYPE_SINK_BUFFER,
CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM,
CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM,
};
This should be fine without any impact on the existing code, as we
expect the driver modules to be updated with the new core module.
Suzuki
>
> 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
>>>
>>
>>
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