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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c76ad00a246sm1563954a12.16.2026.03.31.02.33.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 31 Mar 2026 02:33:49 -0700 (PDT) Message-ID: Date: Tue, 31 Mar 2026 17:33:45 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] coresight: tpdm: add traceid_show for checking traceid To: James Clark , Suzuki K Poulose Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Mike Leach , Leo Yan , Alexander Shishkin , Tingwei Zhang References: <20260325-add-traceid-show-for-tpdm-v3-1-0eb836d4ec30@oss.qualcomm.com> <95610981-ad68-4a31-a776-27894b7bca59@linaro.org> <207b78e5-ed6b-4caf-b9ce-546cf33d6dfd@oss.qualcomm.com> <7abe93fa-3748-4077-b75a-d28296862654@linaro.org> Content-Language: en-US From: Jie Gan In-Reply-To: <7abe93fa-3748-4077-b75a-d28296862654@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzMxMDA5MSBTYWx0ZWRfX3XY8RqAqQiO/ 1izylxMWGXMjvB4h7OFc96CVq6EBA6hMMCY9qP+Kl7n2w++672xSBX6R0yCDyTJ1C4iSxxdZNJZ E4XUd51DRux7OQr7PbBIjyBg5qZ1XyI2So9sEYXt3a1hVe124PpnfDjbU28Ug+2Xsqsct+wcOJJ C6CA5+dS65dIDzHC06Kjh72+9FX+AvW+TUOKl/D1g6ti3M58ur40kutnv9S0uHXwP/fPPYoGcwi kaacRG5TzN+OG9HFwuGY5S9nPK1XSxBjoa4ZgPfxcmvXmDwnEQamuEfnvNeiUd/qlD2c6/meiA1 RWIQJ1KVJ4q0zDKpokbyy+wJOqQf1iBHXsmMbBiSiEIs8SF6S5wfzZi92ajW+oyI0+upjPNVLvb 5ZOMZsxeDreChp44+6WIudboiy6qQhoB5GxI9/n6woHQFDG2gnOI8/gWKqHWh3cBWDVyef27WgY KzbL2tmPxycOdgWR/QQ== X-Proofpoint-ORIG-GUID: e_z6_khoNCTEgKX8yJM-ISea-0PQPzcc X-Proofpoint-GUID: e_z6_khoNCTEgKX8yJM-ISea-0PQPzcc X-Authority-Analysis: v=2.4 cv=NLjYOk6g c=1 sm=1 tr=0 ts=69cb94ff cx=c_pps a=UNFcQwm+pnOIJct1K4W+Mw==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=DJpcGTmdVt4CTyJn9g5Z:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=vnwuCBEG_e02qIenT_YA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=uKXjsCUrEbL0IQVhDsJ9:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-31_02,2026-03-28_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 suspectscore=0 impostorscore=0 spamscore=0 phishscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 lowpriorityscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603310091 On 3/31/2026 5:26 PM, James Clark wrote: > > > On 31/03/2026 4:18 am, Jie Gan wrote: >> Hi James, >> >> On 3/31/2026 9:29 AM, Jie Gan wrote: >>> >>> Hi James, >>> >>> On 3/30/2026 10:55 PM, James Clark wrote: >>>> >>>> >>>> On 25/03/2026 3:10 am, Jie Gan wrote: >>>>> Save the trace ID in drvdata during TPDM enablement and expose it >>>>> to userspace to support trace data parsing. >>>>> >>>>> The TPDM device’s trace ID corresponds to the trace ID allocated >>>>> to the connected TPDA device. >>>>> >>>>> Signed-off-by: Jie Gan >>>>> --- >>>>> Changes in v3: >>>>> 1. Only allow user to read the traceid while the TPDM device is >>>>> enabled. >>>>> - Link to v2: https://lore.kernel.org/r/20260316-add-traceid-show- >>>>> for- tpdm-v2-1-1dec2a67e4ed@oss.qualcomm.com >>>>> >>>>> Changes in V2: >>>>> 1. Use sysfs_emit instead of sprintf. >>>>> Link to V1 - https://lore.kernel.org/all/20260306-add-traceid-show- >>>>> for-tpdm-v1-1-0658a8edb972@oss.qualcomm.com/ >>>>> --- >>>>>   drivers/hwtracing/coresight/coresight-tpdm.c | 34 +++++++++++++++ >>>>> + + + +++++++++- >>>>>   drivers/hwtracing/coresight/coresight-tpdm.h |  2 ++ >>>>>   2 files changed, 35 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c b/ >>>>> drivers/ hwtracing/coresight/coresight-tpdm.c >>>>> index da77bdaad0a4..c8339b973bfc 100644 >>>>> --- a/drivers/hwtracing/coresight/coresight-tpdm.c >>>>> +++ b/drivers/hwtracing/coresight/coresight-tpdm.c >>>>> @@ -481,7 +481,7 @@ static void __tpdm_enable(struct tpdm_drvdata >>>>> *drvdata) >>>>>   static int tpdm_enable(struct coresight_device *csdev, struct >>>>> perf_event *event, >>>>>                  enum cs_mode mode, >>>>> -               __maybe_unused struct coresight_path *path) >>>>> +               struct coresight_path *path) >>>>>   { >>>>>       struct tpdm_drvdata *drvdata = dev_get_drvdata(csdev- >>>>> >dev.parent); >>>>> @@ -497,6 +497,7 @@ static int tpdm_enable(struct coresight_device >>>>> *csdev, struct perf_event *event, >>>>>       } >>>>>       __tpdm_enable(drvdata); >>>>> +    drvdata->traceid = path->trace_id; >>>>>       drvdata->enable = true; >>>>>       spin_unlock(&drvdata->spinlock); >>>>> @@ -693,6 +694,29 @@ static struct attribute_group tpdm_attr_grp = { >>>>>       .attrs = tpdm_attrs, >>>>>   }; >>>>> +static ssize_t traceid_show(struct device *dev, >>>>> +                struct device_attribute *attr, char *buf) >>>>> +{ >>>>> +    unsigned long val; >>>>> +    struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent); >>>>> + >>>>> +    if (coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED) >>>>> +        return -EINVAL; >>>>> + >>>>> +    val = drvdata->traceid; >>>> >>>> You probably need to take the coresight_mutex here otherwise you >>>> could still return an invalid or stale value despite checking the mode. >>>> >>> >>> Acked. I have missed this potential race condition. >>> >>>> There might also be some value in it returning the last used trace >>>> ID even if the mode isn't enabled anymore. Because you can still >>>> read out of the sink after disabling, so it makes more sense for a >>>> script to read it at that point rather than when it's enabled. Also, >>>> you probably don't want to be doing other things in your script in >>>> the point between enabling and disabling. >>> >>> That's making sense. I shouldnt add such restriction for the read >>> process. >>> >> >> I missed one point in last message. >> >> Is that acceptable to export the coresight_mutex from the core module? >> Currently, the coresight_mutex is used within the module only. >> >> Thanks, >> Jie >> > > If the plan is to only check for non-zero trace ID and not check the > mode any more then you don't need to lock. Maybe lets see what Suzuki > thinks about returning the last trace ID though as it was his idea to > add -EINVAL. > Sure. The trace ID is allocated during TPDA device probe and remains unchanged for the entire lifetime of the device. Thanks, Jie >>> Scenarios for reading: >>> 1. device is enabled -> trace ID is valid >>> 2. device is enabled then disabled -> trace ID is valid for the last >>> trace event >>> 3. device is never enabled -> invalid trace ID (value 0) >>> >>> we only need to check the validation of the trace ID. >>> >>> mutex_lock(&coresight_mutex); >>> val = drvdata->traceid; >>> mutex_unlock(&coresight_mutex); >>> >>> if (!val) >>>      return -EINVAL; >>> >>> return sysfs_emit(buf, "%#lx\n", val); >>> >>> Thanks, >>> Jie >>> >>>> >>>>> +    return sysfs_emit(buf, "%#lx\n", val); >>>>> +} >>>>> +static DEVICE_ATTR_RO(traceid); >>>>> + >>>>> +static struct attribute *traceid_attrs[] = { >>>>> +    &dev_attr_traceid.attr, >>>>> +    NULL, >>>>> +}; >>>>> + >>>>> +static struct attribute_group traceid_attr_grp = { >>>>> +    .attrs = traceid_attrs, >>>>> +}; >>>>> + >>>>>   static ssize_t dsb_mode_show(struct device *dev, >>>>>                    struct device_attribute *attr, >>>>>                    char *buf) >>>>> @@ -1367,6 +1391,12 @@ static const struct attribute_group >>>>> *tpdm_attr_grps[] = { >>>>>       &tpdm_cmb_patt_grp, >>>>>       &tpdm_cmb_msr_grp, >>>>>       &tpdm_mcmb_attr_grp, >>>>> +    &traceid_attr_grp, >>>>> +    NULL, >>>>> +}; >>>>> + >>>>> +static const struct attribute_group *static_tpdm_attr_grps[] = { >>>>> +    &traceid_attr_grp, >>>>>       NULL, >>>>>   }; >>>>> @@ -1425,6 +1455,8 @@ static int tpdm_probe(struct device *dev, >>>>> struct resource *res) >>>>>       desc.access = CSDEV_ACCESS_IOMEM(base); >>>>>       if (res) >>>>>           desc.groups = tpdm_attr_grps; >>>>> +    else >>>>> +        desc.groups = static_tpdm_attr_grps; >>>>>       drvdata->csdev = coresight_register(&desc); >>>>>       if (IS_ERR(drvdata->csdev)) >>>>>           return PTR_ERR(drvdata->csdev); >>>>> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.h b/ >>>>> drivers/ hwtracing/coresight/coresight-tpdm.h >>>>> index 2867f3ab8186..11da64e1ade8 100644 >>>>> --- a/drivers/hwtracing/coresight/coresight-tpdm.h >>>>> +++ b/drivers/hwtracing/coresight/coresight-tpdm.h >>>>> @@ -300,6 +300,7 @@ struct cmb_dataset { >>>>>    * @cmb         Specifics associated to TPDM CMB. >>>>>    * @dsb_msr_num Number of MSR supported by DSB TPDM >>>>>    * @cmb_msr_num Number of MSR supported by CMB TPDM >>>>> + * @traceid    Trace ID of the path. >>>>>    */ >>>>>   struct tpdm_drvdata { >>>>> @@ -313,6 +314,7 @@ struct tpdm_drvdata { >>>>>       struct cmb_dataset    *cmb; >>>>>       u32            dsb_msr_num; >>>>>       u32            cmb_msr_num; >>>>> +    u8            traceid; >>>>>   }; >>>>>   /* Enumerate members of various datasets */ >>>>> >>>>> --- >>>>> base-commit: b84a0ebe421ca56995ff78b66307667b62b3a900 >>>>> change-id: 20260316-add-traceid-show-for-tpdm-88d040651f00 >>>>> >>>>> Best regards, >>>> >>> >> >