Re: [PATCH v2] coresight: Add a KUnit test for coresight_find_default_sink()

[James Clark <james.clark@linaro.org>]

On 11/03/2025 3:00 pm, Suzuki K Poulose wrote:
> On 05/03/2025 15:07, James Clark wrote:
>> Add a test to confirm that default sink selection skips over an ETF
>> and returns an ETR even if it's further away.
>>
>> This also makes it easier to add new unit tests in the future.
>>
>> Signed-off-by: James Clark <james.clark@linaro.org>
>> ---
>> Changes in v2:
>> - Let devm free everything rather than doing individual kfrees:
>>    "Like with managed drivers, KUnit-managed fake devices are
>>    automatically cleaned up when the test finishes, but can be manually
>>    cleaned up early with kunit_device_unregister()."
>> - Link to v1: https://lore.kernel.org/r/20250225164639.522741-1- 
>> james.clark@linaro.org
>> ---
>>   drivers/hwtracing/coresight/Kconfig                |  9 +++
>>   drivers/hwtracing/coresight/Makefile               |  3 +-
>>   drivers/hwtracing/coresight/coresight-core.c       |  1 +
>>   .../hwtracing/coresight/coresight-kunit-tests.c    | 77 ++++++++++++ 
>> ++++++++++
>>   4 files changed, 88 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/ 
>> coresight/Kconfig
>> index ecd7086a5b83..f064e3d172b3 100644
>> --- a/drivers/hwtracing/coresight/Kconfig
>> +++ b/drivers/hwtracing/coresight/Kconfig
>> @@ -259,4 +259,13 @@ config CORESIGHT_DUMMY
>>         To compile this driver as a module, choose M here: the module 
>> will be
>>         called coresight-dummy.
>> +
>> +config CORESIGHT_KUNIT_TESTS
>> +      tristate "Enable Coresight unit tests"
>> +      depends on KUNIT
>> +      default KUNIT_ALL_TESTS
>> +      help
>> +        Enable Coresight unit tests. Only useful for development and not
>> +        intended for production.
>> +
>>   endif
>> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/ 
>> coresight/Makefile
>> index 8e62c3150aeb..96f0dfedb1bf 100644
>> --- a/drivers/hwtracing/coresight/Makefile
>> +++ b/drivers/hwtracing/coresight/Makefile
>> @@ -51,5 +51,4 @@ 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
>> -obj-$(CONFIG_CORESIGHT_CTCU) += coresight-ctcu.o
>> -coresight-ctcu-y := coresight-ctcu-core.o
>> +obj-$(CONFIG_CORESIGHT_KUNIT_TESTS) += coresight-kunit-tests.o
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/ 
>> hwtracing/coresight/coresight-core.c
>> index bd0a7edd38c9..b101aa133ceb 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -959,6 +959,7 @@ coresight_find_default_sink(struct 
>> coresight_device *csdev)
>>       }
>>       return csdev->def_sink;
>>   }
>> +EXPORT_SYMBOL_GPL(coresight_find_default_sink);
>>   static int coresight_remove_sink_ref(struct device *dev, void *data)
>>   {
>> diff --git a/drivers/hwtracing/coresight/coresight-kunit-tests.c b/ 
>> drivers/hwtracing/coresight/coresight-kunit-tests.c
>> new file mode 100644
>> index 000000000000..a136af05eaf4
>> --- /dev/null
>> +++ b/drivers/hwtracing/coresight/coresight-kunit-tests.c
>> @@ -0,0 +1,77 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +#include <kunit/test.h>
>> +#include <kunit/device.h>
>> +#include <linux/coresight.h>
>> +
>> +#include "coresight-priv.h"
>> +
>> +static struct coresight_device *coresight_test_device(struct device 
>> *dev)
>> +{
>> +    struct coresight_device *csdev = devm_kcalloc(dev, 1,
>> +                             sizeof(struct coresight_device),
>> +                             GFP_KERNEL);
>> +    csdev->pdata = devm_kcalloc(dev, 1,
>> +                   sizeof(struct coresight_platform_data),
>> +                   GFP_KERNEL);
>> +    return csdev;
>> +}
>> +
>> +static int coresight_test_cpuid(struct coresight_device *csdev)
>> +{
>> +    return 0;
>> +}
>> +
>> +static void test_default_sink(struct kunit *test)
>> +{
>> +    /*
>> +     * ETM -> ETF -> ETR -> CATU
>> +     *                ^
>> +     *                | default
>> +     */
>> +    struct device *dev = kunit_device_register(test, "coresight_kunit");
>> +    struct coresight_device *etm = coresight_test_device(dev),
>> +                *etf = coresight_test_device(dev),
>> +                *etr = coresight_test_device(dev),
>> +                *catu = coresight_test_device(dev);
>> +    struct coresight_connection conn = {};
>> +    struct coresight_ops_source src_ops = {.cpu_id = 
>> coresight_test_cpuid };
> 
> Do we need the trace_id() ? Why is this required ?
> 
> Suzuki
> 

Because it tests with per-cpu sources so it checks if any of the TRBE 
sinks have been assigned first:

  /* look for a default sink if we have not found for this device */
    if (!csdev->def_sink) {
       if (coresight_is_percpu_source(csdev))
	 csdev->def_sink = per_cpu(csdev_sink,
                                    source_ops(csdev)->cpu_id(csdev));

I think this test would probably fail if run somewhere TRBE was already 
probed. I can make the source subtype to be 
CORESIGHT_DEV_SUBTYPE_SOURCE_BUS for the test to work around it. Any 
value other than CORESIGHT_DEV_SUBTYPE_SOURCE_PROC will work. And then I 
can drop the fake cpu_id() callback.