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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35d9507d505sm8078482a91.10.2026.03.30.18.29.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Mar 2026 18:29:57 -0700 (PDT) Message-ID: Date: Tue, 31 Mar 2026 09:29:52 +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> Content-Language: en-US From: Jie Gan In-Reply-To: <95610981-ad68-4a31-a776-27894b7bca59@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=ErbfbCcA c=1 sm=1 tr=0 ts=69cb2397 cx=c_pps a=RP+M6JBNLl+fLTcSJhASfg==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=pfTpB1fsnbrxJmBpuLMA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=iS9zxrgQBfv6-_F4QbHw:22 X-Proofpoint-ORIG-GUID: NReZnBKUtU9PCuLVO0ChxTd5oAbms1gj X-Proofpoint-GUID: NReZnBKUtU9PCuLVO0ChxTd5oAbms1gj X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzMxMDAxMSBTYWx0ZWRfX9CTrdtuNeHSU gzA2H0XB/tIdOuVDCNYcB5VNcS8xHK5wGYJbUNxOnKntPKw622p3xzyXzxYSwq0zHqAd/N+tcdA LZWdryJaBB37wC4MeogxJdoXi6K/8ueS0fTsK97ohWBmhj8C9uh/qghwUH6MhdIxcW8rbUGSwv0 t1cifrYl1yXFfILlPO/qLjmE8siu07f9bPHmgx66ufkNzpXQQtXzww3xHfiJwOV9dT8A0D8VrLx QYH03eLfvBJCsGbvF7MVv8SXHAxP3lDNBf79Nc0MfTJmzwGgqtZue3F8ISgOuu7NaNzX5nFb1FP vwytPdzK1WyuHdpj3oyAUzoAfF7Zvt93aqxGhTImOq/+jlxiNtxmUrR1FnkwGIS+6bFkWaWIU2a mXHHw3HBcl27rnwusKYa5cmGaihWU1EhGyUVgw5IOMPaMEaebkQc7AuvOBgqA4gNP1Nvt0v/gZI Lu9jUwLDd7gS5q42pHw== 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=2026-03-30_02,2026-03-28_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1015 phishscore=0 spamscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 priorityscore=1501 impostorscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603310011 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. 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, >