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Message-ID: <0faff427-1f01-8783-9585-32dca872fe45@quicinc.com>
Date: Tue, 28 Mar 2023 15:22:45 +0800
From: Hao Zhang <quic_hazha@...cinc.com>
To: Mike Leach <mike.leach@...aro.org>
CC: Mathieu Poirier <mathieu.poirier@...aro.org>,
Suzuki K Poulose <suzuki.poulose@....com>,
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
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.
>
> 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.
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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