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Message-ID: <9fcc59cf-c76e-8cee-d232-830b31e35060@quicinc.com>
Date:   Tue, 28 Mar 2023 17:24:37 +0800
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Subject: Re: [PATCH v2 1/3] Coresight: Add coresight dummy driver
Content-Language: en-US
To:     Suzuki K Poulose <suzuki.poulose@arm.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>
 <883c72a4-0c72-fd08-1b04-577037138b43@arm.com>
From:   Hao Zhang <quic_hazha@quicinc.com>
In-Reply-To: <883c72a4-0c72-fd08-1b04-577037138b43@arm.com>
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Hi Suzuki,

On 3/28/2023 4:35 PM, Suzuki K Poulose wrote:
> 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
> 

Sure, I will take your advice in the next version of patch.

Thanks,
Hao

> 
>>
>> 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
>>>>
>>>
>>>
>