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Message-ID: <883c72a4-0c72-fd08-1b04-577037138b43@arm.com>
Date:   Tue, 28 Mar 2023 09:35:55 +0100
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Subject: Re: [PATCH v2 1/3] Coresight: Add coresight dummy driver
Content-Language: en-US
To:     Hao Zhang <quic_hazha@quicinc.com>,
        Mike Leach <mike.leach@linaro.org>
Cc:     Mathieu Poirier <mathieu.poirier@linaro.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Konrad Dybcio <konradybcio@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Andy Gross <agross@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Jonathan Corbet <corbet@lwn.net>, Leo Yan <leo.yan@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        Tingwei Zhang <quic_tingweiz@quicinc.com>,
        Jinlong Mao <quic_jinlmao@quicinc.com>,
        Yuanfang Zhang <quic_yuanfang@quicinc.com>,
        Tao Zhang <quic_taozha@quicinc.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        linux-arm-msm@vger.kernel.org,
        Bjorn Andersson <andersson@kernel.org>,
        linux-doc@vger.kernel.org
References: <20230324061608.33609-1-quic_hazha@quicinc.com>
 <20230324061608.33609-2-quic_hazha@quicinc.com>
 <CAJ9a7VgAJ25CCGwwdfs2DXKaKYoA-BUQAdyZt5udm4qJf9ZQrA@mail.gmail.com>
 <0faff427-1f01-8783-9585-32dca872fe45@quicinc.com>
From:   Suzuki K Poulose <suzuki.poulose@arm.com>
In-Reply-To: <0faff427-1f01-8783-9585-32dca872fe45@quicinc.com>
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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@quicinc.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@quicinc.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
>>>
>>
>>