CoreSight April 2026

coresight@lists.linaro.org

5 participants
41 discussions

Re: [PATCH 1/2] coresight: etm4x: fix inconsistencies with sysfs configration

by Suzuki K Poulose

Hi Levi On 17/03/2026 18:17, Yeoreum Yun wrote: > The current ETM4x configuration via sysfs can lead to the following > inconsistencies: > > - If a configuration is modified via sysfs while a perf session is > active, the running configuration may differ between before > a sched-out and after a subsequent sched-in. > > - Once a perf session is enabled, some read-only register fields > (e.g., TRCSSCSR<n>) may not be reported correctly, > because drvdata->config is cleared while enabling with perf mode, > even though the information was previously read via etm4_init_arch_data(). Thank you for the patch. The patch looks good to me. Some minor comments below. > > To resolve these inconsistencies, the configuration should be separated into: > > - active_config, which represents the currently applied configuration To be more precise, it is the "Applied configuration for the current session" > - config, which stores the settings configured via sysfs. While we are at it, should we stop using the drvdata->config for the "capabilities" for the ETM (e.g., TRCSSCSRn in ss_status ?) Instead we could save it in "drvdata->ss_status". This keeps everything separated: 1. Boot time probed capabilities of ETM 2. Sysfs configuration for the next Run 3. Current active configuration for the ETM (sysfs or perf) Suzuki > > Signed-off-by: Yeoreum Yun <yeoreum.yun(a)arm.com> > --- > .../hwtracing/coresight/coresight-etm4x-cfg.c | 2 +- > .../coresight/coresight-etm4x-core.c | 45 +++++++++++-------- > drivers/hwtracing/coresight/coresight-etm4x.h | 2 + > 3 files changed, 30 insertions(+), 19 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c > index c302072b293a..84213d40d1ae 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c > @@ -47,7 +47,7 @@ static int etm4_cfg_map_reg_offset(struct etmv4_drvdata *drvdata, > struct cscfg_regval_csdev *reg_csdev, u32 offset) > { > int err = -EINVAL, idx; > - struct etmv4_config *drvcfg = &drvdata->config; > + struct etmv4_config *drvcfg = &drvdata->active_config; > u32 off_mask; > > if (((offset >= TRCEVENTCTL0R) && (offset <= TRCVIPCSSCTLR)) || > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c > index d565a73f0042..c552129c4a0c 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > @@ -88,9 +88,11 @@ static int etm4_probe_cpu(unsigned int cpu); > */ > static bool etm4x_sspcicrn_present(struct etmv4_drvdata *drvdata, int n) > { > + struct etmv4_config *config = &drvdata->active_config; > + > return (n < drvdata->nr_ss_cmp) && > drvdata->nr_pe && > - (drvdata->config.ss_status[n] & TRCSSCSRn_PC); > + (config->ss_status[n] & TRCSSCSRn_PC); > } > > u64 etm4x_sysreg_read(u32 offset, bool _relaxed, bool _64bit) > @@ -266,10 +268,11 @@ static void etm4x_prohibit_trace(struct etmv4_drvdata *drvdata) > static u64 etm4x_get_kern_user_filter(struct etmv4_drvdata *drvdata) > { > u64 trfcr = drvdata->trfcr; > + struct etmv4_config *config = &drvdata->active_config; > > - if (drvdata->config.mode & ETM_MODE_EXCL_KERN) > + if (config->mode & ETM_MODE_EXCL_KERN) > trfcr &= ~TRFCR_EL1_ExTRE; > - if (drvdata->config.mode & ETM_MODE_EXCL_USER) > + if (config->mode & ETM_MODE_EXCL_USER) > trfcr &= ~TRFCR_EL1_E0TRE; > > return trfcr; > @@ -277,7 +280,7 @@ static u64 etm4x_get_kern_user_filter(struct etmv4_drvdata *drvdata) > > /* > * etm4x_allow_trace - Allow CPU tracing in the respective ELs, > - * as configured by the drvdata->config.mode for the current > + * as configured by the drvdata->active_config.mode for the current > * session. Even though we have TRCVICTLR bits to filter the > * trace in the ELs, it doesn't prevent the ETM from generating > * a packet (e.g, TraceInfo) that might contain the addresses from > @@ -288,12 +291,13 @@ static u64 etm4x_get_kern_user_filter(struct etmv4_drvdata *drvdata) > static void etm4x_allow_trace(struct etmv4_drvdata *drvdata) > { > u64 trfcr, guest_trfcr; > + struct etmv4_config *config = &drvdata->active_config; > > /* If the CPU doesn't support FEAT_TRF, nothing to do */ > if (!drvdata->trfcr) > return; > > - if (drvdata->config.mode & ETM_MODE_EXCL_HOST) > + if (config->mode & ETM_MODE_EXCL_HOST) > trfcr = drvdata->trfcr & ~(TRFCR_EL1_ExTRE | TRFCR_EL1_E0TRE); > else > trfcr = etm4x_get_kern_user_filter(drvdata); > @@ -301,7 +305,7 @@ static void etm4x_allow_trace(struct etmv4_drvdata *drvdata) > write_trfcr(trfcr); > > /* Set filters for guests and pass to KVM */ > - if (drvdata->config.mode & ETM_MODE_EXCL_GUEST) > + if (config->mode & ETM_MODE_EXCL_GUEST) > guest_trfcr = drvdata->trfcr & ~(TRFCR_EL1_ExTRE | TRFCR_EL1_E0TRE); > else > guest_trfcr = etm4x_get_kern_user_filter(drvdata); > @@ -494,7 +498,7 @@ static int etm4_enable_trace_unit(struct etmv4_drvdata *drvdata) > static int etm4_enable_hw(struct etmv4_drvdata *drvdata) > { > int i, rc; > - struct etmv4_config *config = &drvdata->config; > + struct etmv4_config *config = &drvdata->active_config; > struct coresight_device *csdev = drvdata->csdev; > struct device *etm_dev = &csdev->dev; > struct csdev_access *csa = &csdev->access; > @@ -666,7 +670,7 @@ static int etm4_config_timestamp_event(struct etmv4_drvdata *drvdata, > { > int ctridx; > int rselector; > - struct etmv4_config *config = &drvdata->config; > + struct etmv4_config *config = &drvdata->active_config; > > /* No point in trying if we don't have at least one counter */ > if (!drvdata->nr_cntr) > @@ -749,7 +753,7 @@ static int etm4_parse_event_config(struct coresight_device *csdev, > { > int ret = 0; > struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent); > - struct etmv4_config *config = &drvdata->config; > + struct etmv4_config *config = &drvdata->active_config; > struct perf_event_attr max_timestamp = { > .ATTR_CFG_FLD_timestamp_CFG = U64_MAX, > }; > @@ -911,14 +915,17 @@ static int etm4_enable_sysfs(struct coresight_device *csdev, struct coresight_pa > > /* enable any config activated by configfs */ > cscfg_config_sysfs_get_active_cfg(&cfg_hash, &preset); > + > + raw_spin_lock(&drvdata->spinlock); > + > + drvdata->active_config = drvdata->config; > + > if (cfg_hash) { > ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset); > if (ret) > return ret; > } > > - raw_spin_lock(&drvdata->spinlock); > - > drvdata->trcid = path->trace_id; > > /* Tracer will never be paused in sysfs mode */ > @@ -1028,7 +1035,7 @@ static void etm4_disable_trace_unit(struct etmv4_drvdata *drvdata) > static void etm4_disable_hw(struct etmv4_drvdata *drvdata) > { > u32 control; > - struct etmv4_config *config = &drvdata->config; > + struct etmv4_config *config = &drvdata->active_config; > struct coresight_device *csdev = drvdata->csdev; > struct csdev_access *csa = &csdev->access; > int i; > @@ -1374,12 +1381,14 @@ static void etm4_init_arch_data(void *info) > u32 etmidr5; > struct etm4_init_arg *init_arg = info; > struct etmv4_drvdata *drvdata; > + struct etmv4_config *config; > struct csdev_access *csa; > struct device *dev = init_arg->dev; > int i; > > drvdata = dev_get_drvdata(init_arg->dev); > csa = init_arg->csa; > + config = &drvdata->active_config; > > /* > * If we are unable to detect the access mechanism, > @@ -1440,7 +1449,7 @@ static void etm4_init_arch_data(void *info) > > /* EXLEVEL_S, bits[19:16] Secure state instruction tracing */ > drvdata->s_ex_level = FIELD_GET(TRCIDR3_EXLEVEL_S_MASK, etmidr3); > - drvdata->config.s_ex_level = drvdata->s_ex_level; > + config->s_ex_level = drvdata->s_ex_level; > /* EXLEVEL_NS, bits[23:20] Non-secure state instruction tracing */ > drvdata->ns_ex_level = FIELD_GET(TRCIDR3_EXLEVEL_NS_MASK, etmidr3); > /* > @@ -1491,8 +1500,7 @@ static void etm4_init_arch_data(void *info) > */ > drvdata->nr_ss_cmp = FIELD_GET(TRCIDR4_NUMSSCC_MASK, etmidr4); > for (i = 0; i < drvdata->nr_ss_cmp; i++) { > - drvdata->config.ss_status[i] = > - etm4x_relaxed_read32(csa, TRCSSCSRn(i)); > + config->ss_status[i] = etm4x_relaxed_read32(csa, TRCSSCSRn(i)); > } > /* NUMCIDC, bits[27:24] number of Context ID comparators for tracing */ > drvdata->numcidc = FIELD_GET(TRCIDR4_NUMCIDC_MASK, etmidr4); > @@ -1685,7 +1693,7 @@ static void etm4_set_default(struct etmv4_config *config) > static int etm4_get_next_comparator(struct etmv4_drvdata *drvdata, u32 type) > { > int nr_comparator, index = 0; > - struct etmv4_config *config = &drvdata->config; > + struct etmv4_config *config = &drvdata->active_config; > > /* > * nr_addr_cmp holds the number of comparator _pair_, so time 2 > @@ -1726,7 +1734,7 @@ static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, > { > int i, comparator, ret = 0; > u64 address; > - struct etmv4_config *config = &drvdata->config; > + struct etmv4_config *config = &drvdata->active_config; > struct etm_filters *filters = event->hw.addr_filters; > > if (!filters) > @@ -2246,7 +2254,8 @@ static int etm4_add_coresight_dev(struct etm4_init_arg *init_arg) > if (!desc.name) > return -ENOMEM; > > - etm4_set_default(&drvdata->config); > + etm4_set_default(&drvdata->active_config); > + drvdata->config = drvdata->active_config; > > pdata = coresight_get_platform_data(dev); > if (IS_ERR(pdata)) > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h > index 89d81ce4e04e..76beb896f188 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x.h > +++ b/drivers/hwtracing/coresight/coresight-etm4x.h > @@ -1022,6 +1022,7 @@ struct etmv4_save_state { > * allows tracing at all ELs. We don't want to compute this > * at runtime, due to the additional setting of TRFCR_CX when > * in EL2. Otherwise, 0. > + * @active_config: structure holding current applied configuration parameters. > * @config: structure holding configuration parameters. > * @save_state: State to be preserved across power loss > * @skip_power_up: Indicates if an implementation can skip powering up > @@ -1079,6 +1080,7 @@ struct etmv4_drvdata { > bool skip_power_up : 1; > bool paused : 1; > u64 trfcr; > + struct etmv4_config active_config; > struct etmv4_config config; > struct etmv4_save_state *save_state; > DECLARE_BITMAP(arch_features, ETM4_IMPDEF_FEATURE_MAX);

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CoreSight April 2026