linux-kernel - Re: [PATCH v5 4/7] coresight-tgu: Add TGU decode support

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Message-ID: <a820b7c9-0919-4c78-a5cc-bf8289dd0b59@quicinc.com>
Date: Fri, 6 Jun 2025 10:56:33 +0800
From: songchai <quic_songchai@...cinc.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC: Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach
	<mike.leach@...aro.org>, James Clark <james.clark@....com>,
        Alexander
 Shishkin <alexander.shishkin@...ux.intel.com>,
        Andy Gross
	<agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring
	<robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
	<conor+dt@...nel.org>, <linux-kernel@...r.kernel.org>,
        <coresight@...ts.linaro.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 4/7] coresight-tgu: Add TGU decode support


On 5/29/2025 7:32 PM, Jonathan Cameron wrote:
> On Thu, 29 May 2025 16:19:45 +0800
> Songwei Chai <quic_songchai@...cinc.com> wrote:
>
>> Decoding is when all the potential pieces for creating a trigger
>> are brought together for a given step. Example - there may be a
>> counter keeping track of some occurrences and a priority-group that
>> is being used to detect a pattern on the sense inputs. These 2
>> inputs to condition_decode must be programmed, for a given step,
>> to establish the condition for the trigger, or movement to another
>> steps.
>>
>> Signed-off-by: Songwei Chai <quic_songchai@...cinc.com>
>> diff --git a/drivers/hwtracing/coresight/coresight-tgu.c b/drivers/hwtracing/coresight/coresight-tgu.c
>> index 6dbfd4c604b1..8dbe8ab30174 100644
>> --- a/drivers/hwtracing/coresight/coresight-tgu.c
>> +++ b/drivers/hwtracing/coresight/coresight-tgu.c
>> @@ -21,13 +21,35 @@ static int calculate_array_location(struct tgu_drvdata *drvdata,
>> +
>>   static int tgu_enable(struct coresight_device *csdev, enum cs_mode mode,
>>   		      void *data)
>>   {
>> +	int ret = 0;
>  From what can be seen here, looks like ret is always set, so no need to init.
Would this initialization improve the determinism of the code? :-)
>>   	struct tgu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>>   
>>   	spin_lock(&drvdata->spinlock);
>> @@ -150,11 +264,15 @@ static int tgu_enable(struct coresight_device *csdev, enum cs_mode mode,
>>   		spin_unlock(&drvdata->spinlock);
>>   		return -EBUSY;
>>   	}
>> -	tgu_write_all_hw_regs(drvdata);
>> +	ret = tgu_write_all_hw_regs(drvdata);
>> +
>> +	if (ret == -EINVAL)
>> +		goto exit;
>>   	drvdata->enable = true;
>>   
>> +exit:
>>   	spin_unlock(&drvdata->spinlock);
>> -	return 0;
>> +	return ret;
>>   }
>> diff --git a/drivers/hwtracing/coresight/coresight-tgu.h b/drivers/hwtracing/coresight/coresight-tgu.h
>> index f07ead505365..691da393ffa3 100644
>> --- a/drivers/hwtracing/coresight/coresight-tgu.h
>> +++ b/drivers/hwtracing/coresight/coresight-tgu.h
>>   enum operation_index {
>>   	TGU_PRIORITY0,
>>   	TGU_PRIORITY1,
>>   	TGU_PRIORITY2,
>> -	TGU_PRIORITY3
>> +	TGU_PRIORITY3,
> And here is why the previous patch should definitely have had the ,
Thanks for your clarification.
>
>> +	TGU_CONDITION_DECODE
>>   
>>   };
>>