Re: [PATCH V3 08/14] coresight: core: Add support for dedicated percpu sinks

From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Suzuki K Poulose <suzuki.poulose@arm.com>,
	linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org
Cc: mathieu.poirier@linaro.org, mike.leach@linaro.org,
	lcherian@marvell.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V3 08/14] coresight: core: Add support for dedicated percpu sinks
Date: Tue, 16 Feb 2021 15:51:38 +0530	[thread overview]
Message-ID: <14f558ff-25d0-8a64-f5b3-38422dbcd69b@arm.com> (raw)
In-Reply-To: <dce24164-d35b-d9d9-2fcd-e50a1bac0b38@arm.com>

On 1/28/21 2:46 PM, Suzuki K Poulose wrote:
> On 1/27/21 8:55 AM, Anshuman Khandual wrote:
>> Add support for dedicated sinks that are bound to individual CPUs. (e.g,
>> TRBE). To allow quicker access to the sink for a given CPU bound source,
>> keep a percpu array of the sink devices. Also, add support for building
>> a path to the CPU local sink from the ETM.
>>
>> This adds a new percpu sink type CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM.
>> This new sink type is exclusively available and can only work with percpu
>> source type device CORESIGHT_DEV_SUBTYPE_SOURCE_PERCPU_PROC.
>>
>> This defines a percpu structure that accommodates a single coresight_device
>> which can be used to store an initialized instance from a sink driver. As
>> these sinks are exclusively linked and dependent on corresponding percpu
>> sources devices, they should also be the default sink device during a perf
>> session.
>>
>> Outwards device connections are scanned while establishing paths between a
>> source and a sink device. But such connections are not present for certain
>> percpu source and sink devices which are exclusively linked and dependent.
>> Build the path directly and skip connection scanning for such devices.
>>
>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
>> Cc: Mike Leach <mike.leach@linaro.org>
>> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>> Changes in V3:
>>
>> - Updated coresight_find_default_sink()
>>
>>   drivers/hwtracing/coresight/coresight-core.c | 16 ++++++++++++++--
>>   include/linux/coresight.h                    | 12 ++++++++++++
>>   2 files changed, 26 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
>> index 0062c89..4795e28 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -23,6 +23,7 @@
>>   #include "coresight-priv.h"
>>     static DEFINE_MUTEX(coresight_mutex);
>> +DEFINE_PER_CPU(struct coresight_device *, csdev_sink);
>>     /**
>>    * struct coresight_node - elements of a path, from source to sink
>> @@ -784,6 +785,13 @@ static int _coresight_build_path(struct coresight_device *csdev,
>>       if (csdev == sink)
>>           goto out;
>>   +    if (coresight_is_percpu_source(csdev) && coresight_is_percpu_sink(sink) &&
>> +        sink == per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev))) {
>> +        _coresight_build_path(sink, sink, path);
>> +        found = true;
>> +        goto out;
>> +    }
>> +
>>       /* Not a sink - recursively explore each port found on this element */
>>       for (i = 0; i < csdev->pdata->nr_outport; i++) {
>>           struct coresight_device *child_dev;
>> @@ -999,8 +1007,12 @@ coresight_find_default_sink(struct coresight_device *csdev)
>>       int depth = 0;
>>         /* look for a default sink if we have not found for this device */
>> -    if (!csdev->def_sink)
>> -        csdev->def_sink = coresight_find_sink(csdev, &depth);
>> +    if (!csdev->def_sink) {
>> +        if (coresight_is_percpu_source(csdev))
>> +            csdev->def_sink = per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev));
>> +        if (!csdev->def_sink)
>> +            csdev->def_sink = coresight_find_sink(csdev, &depth);
>> +    }
>>       return csdev->def_sink;
>>   }
>>   diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>> index 976ec26..bc3a5ca 100644
>> --- a/include/linux/coresight.h
>> +++ b/include/linux/coresight.h
>> @@ -50,6 +50,7 @@ enum coresight_dev_subtype_sink {
>>       CORESIGHT_DEV_SUBTYPE_SINK_PORT,
>>       CORESIGHT_DEV_SUBTYPE_SINK_BUFFER,
>>       CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM,
>> +    CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM,
>>   };
>>     enum coresight_dev_subtype_link {
>> @@ -428,6 +429,17 @@ static inline void csdev_access_write64(struct csdev_access *csa, u64 val, u32 o
>>           csa->write(val, offset, false, true);
>>   }
>>   +static inline bool coresight_is_percpu_source(struct coresight_device *csdev)
>> +{
>> +    return csdev && (csdev->type == CORESIGHT_DEV_TYPE_SOURCE) &&
>> +           csdev->subtype.source_subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_PROC;
> 
> Please add () around the last line. Same below.

Okay, will do.

> 
>> +}
>> +
>> +static inline bool coresight_is_percpu_sink(struct coresight_device *csdev)
>> +{
>> +    return csdev && (csdev->type == CORESIGHT_DEV_TYPE_SINK) &&
>> +           csdev->subtype.sink_subtype == CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM;

Okay, will add here as well.

>> +}
>>   #else    /* !CONFIG_64BIT */
>>     static inline u64 csdev_access_relaxed_read64(struct csdev_access *csa,
>>
> 
> With the above :
> 
> Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>