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Message-ID: <d0be9671-bb32-e306-0a0f-c706837df994@quicinc.com>
Date:   Fri, 28 Apr 2023 13:35:50 +0800
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Subject: Re: [PATCH v3 1/3] Coresight: Add coresight dummy driver
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To:     Suzuki K Poulose <suzuki.poulose@arm.com>,
        Mike Leach <mike.leach@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        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>
CC:     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: <20230422073714.38844-1-quic_hazha@quicinc.com>
 <20230422073714.38844-2-quic_hazha@quicinc.com>
 <6ca3de6d-eaba-f9c1-1809-90902a69564a@arm.com>
From:   Hao Zhang <quic_hazha@quicinc.com>
In-Reply-To: <6ca3de6d-eaba-f9c1-1809-90902a69564a@arm.com>
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Precedence: bulk

Hi Suzuki,

On 4/24/2023 8:09 PM, Suzuki K Poulose wrote:
> 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
> 
This is required for ATID filtering funtion which is our HW design for 
ETR, we need to set traceid/atid for etm, stm and tpda. Therefore, it's 
needed if the type of dummy source is etm. This part is waiting for 
upstream. I will remove it now and upstream it as the part of ATID 
filtering in the further.

Thanks,
Hao