CoreSight

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2839 discussions

[PATCH v2] coresight: trbe: Hide enable_sink sysfs file

by James Clark

TRBE doesn't support sysfs mode, but the enable_sink file can still be successfully written to enable the device, and only attempting to enable the source would later fail. Avoid misleading users by adding a flag that devices can use to hide either the enable_sink or enable_source files, and set it for TRBE. Don't set it for ETE as it's possible that ETE could appear on the legacy bus and work with sysfs, and writing to enable_source already reports EINVAL if the device doesn't support sysfs mode. Signed-off-by: James Clark <james.clark(a)linaro.org> --- Changes in v2: - Re-use CORESIGHT_DESC flags in csdev instead of converting to bool. - Hide all remaining attrs after label instead of only source and sink attrs as there aren't any others anyway (Leo). - Link to v1: https://lore.kernel.org/r/20260507-james-cs-hide-trbe-enable-v1-1-b4e40439f… --- drivers/hwtracing/coresight/coresight-core.c | 1 + drivers/hwtracing/coresight/coresight-sysfs.c | 15 +++++++++------ drivers/hwtracing/coresight/coresight-trbe.c | 7 +++++++ include/linux/coresight.h | 4 ++++ 4 files changed, 21 insertions(+), 6 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index f7b1308a759c..a0c098980096 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -1543,6 +1543,7 @@ coresight_init_device(struct coresight_desc *desc) csdev->ops = desc->ops; csdev->access = desc->access; csdev->orphan = true; + csdev->flags = desc->flags; if (desc->flags & CORESIGHT_DESC_CPU_BOUND) { csdev->cpu = desc->cpu; diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c index 4b010f8bc4c0..75000fe64fda 100644 --- a/drivers/hwtracing/coresight/coresight-sysfs.c +++ b/drivers/hwtracing/coresight/coresight-sysfs.c @@ -346,16 +346,19 @@ static ssize_t label_show(struct device *dev, } static DEVICE_ATTR_RO(label); -static umode_t label_is_visible(struct kobject *kobj, - struct attribute *attr, int n) +static umode_t coresight_attr_is_visible(struct kobject *kobj, + struct attribute *attr, int n) { struct device *dev = kobj_to_dev(kobj); + struct coresight_device *csdev = to_coresight_device(dev); if (attr == &dev_attr_label.attr) { if (fwnode_property_present(dev_fwnode(dev), "label")) return attr->mode; else return 0; + } else if (csdev->flags & CORESIGHT_DESC_NO_SYSFS_MODE) { + return 0; } return attr->mode; @@ -369,7 +372,7 @@ static struct attribute *coresight_sink_attrs[] = { static struct attribute_group coresight_sink_group = { .attrs = coresight_sink_attrs, - .is_visible = label_is_visible, + .is_visible = coresight_attr_is_visible, }; __ATTRIBUTE_GROUPS(coresight_sink); @@ -381,7 +384,7 @@ static struct attribute *coresight_source_attrs[] = { static struct attribute_group coresight_source_group = { .attrs = coresight_source_attrs, - .is_visible = label_is_visible, + .is_visible = coresight_attr_is_visible, }; __ATTRIBUTE_GROUPS(coresight_source); @@ -392,7 +395,7 @@ static struct attribute *coresight_link_attrs[] = { static struct attribute_group coresight_link_group = { .attrs = coresight_link_attrs, - .is_visible = label_is_visible, + .is_visible = coresight_attr_is_visible, }; __ATTRIBUTE_GROUPS(coresight_link); @@ -403,7 +406,7 @@ static struct attribute *coresight_helper_attrs[] = { static struct attribute_group coresight_helper_group = { .attrs = coresight_helper_attrs, - .is_visible = label_is_visible, + .is_visible = coresight_attr_is_visible, }; __ATTRIBUTE_GROUPS(coresight_helper); diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c index c7cbca45f2de..eca8e13a9744 100644 --- a/drivers/hwtracing/coresight/coresight-trbe.c +++ b/drivers/hwtracing/coresight/coresight-trbe.c @@ -1348,6 +1348,13 @@ static void arm_trbe_register_coresight_cpu(struct trbe_drvdata *drvdata, int cp desc.dev = dev; desc.cpu = cpu; desc.flags = CORESIGHT_DESC_CPU_BOUND; + /* + * ETE isn't connected to TRBE with a link like other Coresight devices + * and the TRBE driver has been written to always assume Perf mode, so + * Prevent sysfs from being used. + */ + desc.flags |= CORESIGHT_DESC_NO_SYSFS_MODE; + trbe_csdev = coresight_register(&desc); if (IS_ERR(trbe_csdev)) goto cpu_clear; diff --git a/include/linux/coresight.h b/include/linux/coresight.h index add0579cad88..6cd1d01b843b 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -142,6 +142,8 @@ struct csdev_access { }) #define CORESIGHT_DESC_CPU_BOUND BIT(0) +/* Device can't be activated from sysfs, only via Perf. */ +#define CORESIGHT_DESC_NO_SYSFS_MODE BIT(1) /** * struct coresight_desc - description of a component required from drivers @@ -310,6 +312,8 @@ struct coresight_device { struct list_head config_csdev_list; raw_spinlock_t cscfg_csdev_lock; void *active_cscfg_ctxt; + /* CORESIGHT_DESC_[x] flags */ + u32 flags; }; /* --- base-commit: c8eb4a8dd259fb2b215da32764fa8c6c76519896 change-id: 20260506-james-cs-hide-trbe-enable-3c8d784e72d8 Best regards, -- James Clark <james.clark(a)linaro.org>

4 weeks, 1 day

[PATCH 0/2] perf/arm: Prefer large AUX mappings for CoreSight and SPE

by Leo Yan

Since the commit: 18049c8cff9 ("perf/aux: Allocate non-contiguous AUX pages by default") it changed the AUX buffer allocator to allocate AUX pages page-by-page (order=0) unless a PMU explicitly asks for contiguous allocations via the capability flag PERF_PMU_CAP_AUX_PREFER_LARGE. The goal was to make AUX allocation more memory-friendly by default, because not all PMUs require physically contiguous AUX pages and large contiguous allocations can contribute to fragmentation on long-running systems. However, Arm SPE and CoreSight/TRBE rely on page-table translation when writing trace data to memory. With page-by-page AUX allocation, a large AUX buffer is mapped with many small mappings. This increases TLB pressure, in practice this can increase trace-buffer latency due to table translation walks (TTW) and contribute to trace discontinuities. This series restores large AUX allocation for Arm CoreSight and SPE by setting PERF_PMU_CAP_AUX_PREFER_LARGE. This is intended to work together with the mm large-mapping series [1]. That series allows vmap() to map physically contiguous pages with larger granules. With this series, perf first tries larger-order AUX allocations, and the vmap() code can then create larger mappings for the contiguous chunks. The fragmentation concern from commit 18049c8cff9c should not block this opt-in. PERF_PMU_CAP_AUX_PREFER_LARGE is a preference, not a hard requirement. The AUX allocator already falls back to smaller orders when a high-order allocation fails. So this series gives Arm trace PMUs the performance benefit when large chunks are available. The comparison below uses a baseline that already includes the mm large-mapping series [1]. "Baseline" means that the mm series is applied but this Arm PMU series is not. "Large AUX" means the same kernel plus this series. Some configurations to mitigate noise during test: 1) The tests were run with CPU10 isolated with the kernel parameter "isolcpus=10". 2) CPU10 was used as the traced CPU, the PMU counter CPU, and the workload CPU. The perf control tasks were pinned to CPU2 so that they did not add extra work on CPU10. 3) Each test was run for 10 iterations, and the tables report the average counter values across those runs. The results show that using larger AUX mappings reduces the TLB pressure. This is mainly visible in the refill events: CoreSight/TRBE shows a large drop in l2d_tlb_refill and a smaller reduction in l1d_tlb_refill, while SPE also reduces l2d_tlb_refill. The dtlb_walk event also drops in both tests, which shows fewer data TLB walks after the AUX buffer can be mapped with larger granules. ETM sparse branch delay (cs_etm, AUX 1GB) taskset -c 2 perf stat -C 10 -e cycles:u,instructions:u,dtlb_walk:u,l1d_tlb:u,l1d_tlb_refill:u,l2d_tlb_refill:u \ -- taskset -c 2 perf record -C 10 -m ,1G -e cs_etm// \ -- taskset -c 10 ./sparse_branch_delay.elf | | Baseline | Large map | | | | Metric | Avg. | Avg. | Delta | Change | |----------------+-----------+-----------+------------+---------| | dtlb_walk | 72.8 | 63.9 | -8.9 | -12.23% | | l1d_tlb | 7,434.4 | 1,982.2 | -5,452.2 | -73.34% | | l1d_tlb_refill | 163.7 | 148.2 | -15.5 | -9.47% | | l2d_tlb_refill | 161,884.9 | 513.1 | -161,371.8 | -99.68% | SPE dd memory copy (arm_spe, AUX 512MB) taskset -c 2 perf stat -C 10 -e cycles:u,instructions:u,dtlb_walk:u,l1d_tlb:u,l1d_tlb_refill:u,l2d_tlb_refill:u \ -- taskset -c 2 perf record -C 10 -m ,512M -e arm_spe_0/ts_enable=1,pa_enable=1,period=64,min_latency=0/ \ -- taskset -c 10 dd if=/dev/zero of=/dev/shm/dd_mem_test bs=1M count=1024 status=progress | | Baseline | Large map | | | | Metric | Avg. | Avg. | Delta | Change | |----------------+-----------+-----------+------------+---------| | dtlb_walk | 1,760.2 | 1,387.9 | -372.3 | -21.15% | | l1d_tlb | 257,312.4 | 251,460.9 | -5,851.5 | -2.27% | | l1d_tlb_refill | 15,921.9 | 15,933.6 | 11.7 | +0.07% | | l2d_tlb_refill | 4,285.0 | 2,796.5 | -1,488.5 | -34.74% | Note that after setting PREFER_LARGE for CoreSight and SPE, the existing AUX trace drivers either prefer large pages or, in the case of Intel BTS/PT, use the stronger AUX_NO_SG constraint. We can refactor this later by either dropping PREFER_LARGE entirely or reversing the flag if a driver needs discrete pages. For now, keep PREFER_LARGE to preserve flexibility in the allocation policy. [1] https://lore.kernel.org/linux-mm/20260715120813.3609949-1-jiangwen6@xiaomi.… Signed-off-by: Leo Yan <leo.yan(a)arm.com> --- Dev Jain (1): coresight: perf: Prefer large AUX mappings Leo Yan (1): perf: arm_spe: Prefer large AUX mappings drivers/hwtracing/coresight/coresight-etm-perf.c | 3 ++- drivers/perf/arm_spe_pmu.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) --- base-commit: db2ddb87143519e20a95aa36c60b36107b736a58 change-id: 20260717-perf_aux_trace_large_granule-d9b30cc14b5a Best regards, -- Leo Yan <leo.yan(a)arm.com>

1 month

[GIT PULL] coresight: Updates for Linux v7.3

by Suzuki K Poulose

Hi Greg Please find this pull request for CoreSight subsystem targeting v7.3. Almost all of them are fixes to the existing code, along with a MAINTAINERS update for HiSilicon PTT driver. Kindly pull Suzuki The following changes since commit 8cdeaa50eae8dad34885515f62559ee83e7e8dda: Linux 7.2-rc2 (2026-07-05 14:44:06 -1000) are available in the Git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/coresight/linux.git tags/coresight-next-v7.3 for you to fetch changes up to 9e3604d7369cfc0110100eb1a0acab1865ee2d18: coresight: etm4x: remove redundant fields in etmv4_save_state (2026-08-07 10:45:11 +0100) ---------------------------------------------------------------- coresight: Updates for Linux v7.3 This is relatively smaller update for CoreSight/hwtracing subsystem updates. - MAINTAINERS update for HiSilicon PCI Trace & Tune drivers - Minor fixes to hisi_ptt driver - Various fixes to the coresight etm4x dirvers Signed-off-by: Suzuki K Poulose <suzuki.poulose(a)arm.com> ---------------------------------------------------------------- Jonathan Cameron (1): MAINTAINERS: Update HiSilicon PCI Trace and Tune maintainer Kuan-Wei Chiu (1): coresight: etm3x: Fix cntr_val_show() to match cntr_val_store() behavior Sanman Pradhan (2): hwtracing: hisi_ptt: Propagate DMA reset timeout in trace_start() hwtracing: hisi_ptt: Remove unnecessary trace buffer zeroing in trace_start() Yeoreum Yun (5): coresight: etm4x: fix wrong check of etm4x_sspcicrn_present() coresight: etm4x: fix underflow for usage of (nrseqstate - 1) coresight: etm4x: fix leaked trace id coresight: etm4x: missing cscfg_csdev_disable_active_config() in perf enable coresight: etm4x: remove redundant fields in etmv4_save_state MAINTAINERS | 3 +- .../hwtracing/coresight/coresight-etm3x-sysfs.c | 15 ++---- drivers/hwtracing/coresight/coresight-etm4x-cfg.c | 2 +- drivers/hwtracing/coresight/coresight-etm4x-core.c | 59 +++++++++++++--------- .../hwtracing/coresight/coresight-etm4x-sysfs.c | 6 ++- drivers/hwtracing/coresight/coresight-etm4x.h | 12 ++--- drivers/hwtracing/ptt/hisi_ptt.c | 25 ++++----- 7 files changed, 63 insertions(+), 59 deletions(-)

1 month

Re: [PATCH v1] coresight: Check runtime PM resume result

by Anshuman Khandual

On 03/08/26 4:55 AM, Yuho Choi wrote: > coresight_get_ref() ignores the return value of pm_runtime_get_sync() > and reports success even when runtime resume fails. A path is then built > and the CoreSight device may be accessed while it remains powered off. > > Use pm_runtime_resume_and_get() so a failed resume is reported and its > runtime PM usage reference is rolled back. Drop the module and device > references acquired before the resume attempt when it fails. > > Fixes: 5da5325fa856 ("coresight: moving PM runtime operations to core framework") > Signed-off-by: Yuho Choi <dbgh9129(a)gmail.com> > --- Should 'Fixes:' be tagging the following commit - which had introduced coresight_get_ref() unconditionally calling pm_runtime_get_sync() ? 32b0707a4182 ("coresight: Add try_get_module() in coresight_grab_device()") > drivers/hwtracing/coresight/coresight-core.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c > index 6d65c43d574f..77d05b360484 100644 > --- a/drivers/hwtracing/coresight/coresight-core.c > +++ b/drivers/hwtracing/coresight/coresight-core.c > @@ -843,7 +843,11 @@ static bool coresight_get_ref(struct coresight_device *csdev) > goto err_module; > > /* Make sure the device is powered on */ > - pm_runtime_get_sync(parent); > + if (pm_runtime_resume_and_get(parent) < 0) { > + module_put(drv->owner); > + goto err_module; > + } > + > return true; > > err_module:

1 month, 1 week

Re: [PATCH v3] coresight: coresight.h: add '*' to kernel-doc lines

by Anshuman Khandual

On 20/07/26 3:54 AM, Randy Dunlap wrote: > kernel-doc reports 2 (kernel-doc) lines in coresight.h that don't have > a beginning '*' in them, so fix these lines. > > Also convert struct coresight_trace_id_map to kernel-doc format to > remove another warning. > > Warning: include/linux/coresight.h:173 bad line: > connected to @src_port. NULL until the device is created > Warning: include/linux/coresight.h:177 bad line: > needs to be filtered. > Warning: include/linux/coresight.h:236 This comment starts with '/**', > but isn't a kernel-doc comment. > > Fixes: ec9903d6cc34 ("coresight: Add support for trace filtering by source") > Fixes: d49c9cf15f89 ("coresight: Rename connection members to make the direction explicit") > Signed-off-by: Randy Dunlap <rdunlap(a)infradead.org> > --- > v2: rebase & resend > v3: rebase & resend > > Cc: James Clark <james.clark(a)arm.com> > Cc: Tao Zhang <quic_taozha(a)quicinc.com> > Cc: Suzuki K Poulose <suzuki.poulose(a)arm.com> > Cc: coresight(a)lists.linaro.org > Cc: Danilo Krummrich <dakr(a)kernel.org> > Cc: Mike Leach <mike.leach(a)arm.com> > Cc: Leo Yan <leo.yan(a)arm.com> > Cc: linux-arm-kernel(a)lists.infradead.org > --- > include/linux/coresight.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > --- linux-next-20260717.orig/include/linux/coresight.h > +++ linux-next-20260717/include/linux/coresight.h > @@ -177,11 +177,11 @@ struct coresight_desc { > * @dest_port: destination's input port number @src_port is connected to. > * @dest_fwnode: destination component's fwnode handle. > * @dest_dev: a @coresight_device representation of the component > - connected to @src_port. NULL until the device is created > + * connected to @src_port. NULL until the device is created > * @link: Representation of the connection as a sysfs link. > * @filter_src_fwnode: filter source component's fwnode handle. > * @filter_src_dev: a @coresight_device representation of the component that > - needs to be filtered. > + * needs to be filtered. > * > * The full connection structure looks like this, where in_conns store > * references to same connection as the source device's out_conns. > @@ -234,7 +234,7 @@ struct coresight_sysfs_link { > #define CORESIGHT_TRACE_IDS_MAX 128 > > /** > - * Trace ID map. > + * struct coresight_trace_id_map - Trace ID map. > * > * @used_ids: Bitmap to register available (bit = 0) and in use (bit = 1) IDs. > * Initialised so that the reserved IDs are permanently marked as > But still there are more warnings left in the documentation file even after the patch applied. Should they be fixed as well ? ./scripts/kernel-doc -none include/linux/coresight.h Warning: include/linux/coresight.h:216 struct member 'src_dev' not described in 'coresight_connection' Warning: include/linux/coresight.h:216 struct member 'src_refcnt' not described in 'coresight_connection' Warning: include/linux/coresight.h:216 struct member 'dest_refcnt' not described in 'coresight_connection' Warning: include/linux/coresight.h:248 struct member 'cpu_map' not described in 'coresight_trace_id_map' Warning: include/linux/coresight.h:248 struct member 'lock' not described in 'coresight_trace_id_map' Warning: include/linux/coresight.h:312 struct member 'perf_sink_id_map' not described in 'coresight_device' Warning: include/linux/coresight.h:216 struct member 'src_dev' not described in 'coresight_connection' Warning: include/linux/coresight.h:216 struct member 'src_refcnt' not described in 'coresight_connection' Warning: include/linux/coresight.h:216 struct member 'dest_refcnt' not described in 'coresight_connection' Warning: include/linux/coresight.h:248 struct member 'cpu_map' not described in 'coresight_trace_id_map' Warning: include/linux/coresight.h:248 struct member 'lock' not described in 'coresight_trace_id_map' Warning: include/linux/coresight.h:312 struct member 'perf_sink_id_map' not described in 'coresight_device'

1 month, 2 weeks

[PATCH v8 00/13] fix several inconsistencies with sysfs configuration in etmX

by Yeoreum Yun

The current ETMx 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. - If a perf session and sysfs session tries to enable concurrently, configuration from configfs could be corrupted (etm4). - There is chance to corrupt drvdata->config if perf session tries to enabled among handling cscfg_csdev_disable_active_config() in etm4_disable_sysfs() (etm4). To resolve these inconsistencies, the configuration should be separated into: - active_config, which is applied configuration for the current session - config, which stores the settings configured via sysfs. and apply configuration from configfs after taking a mode. Also, This patch set includes some small fixes: - missing trace id release in etm4x. - underflow issue for nrseqstate. - wrong check in etm4x_sspcicrn_present(). - missing call of cscfg_csdev_disable_active_config() This patch based on coresight tree's next Patch History ============= from v7 to v8: - accept @Leo Yan' suggestion to handle error. - small minor fixes following @Suzuki' suggestion. - https://lore.kernel.org/all/20260519154812.254884-1-yeoreum.yun@arm.com/ from v6 to v7: - rebase on coresight/next - add ETM_MAX_SEQ_TRANSITIONS define - remove redundant patch relavent cpu-hotplug as coresight-pm patch merged. - https://lore.kernel.org/all/20260422132203.977549-1-yeoreum.yun@arm.com/ from v5 to v6: - fix missing of calling cscfg_csdev_disable_active_config() - add rb & fixes tags. - add ss_status field in etm4x_drvdata to expose STATUS and PENDING bits. - https://lore.kernel.org/all/20260415165528.3369607-1-yeoreum.yun@arm.com/ from v4 to v5: - add rb-tag. - fix underflow issue for nrseqstate. - fix wrong check in etm4_sspcicrn_present(). - remove redundant fields on etmv4_save_state. - rename caps->ss_status to ss_cmp. - fix wrong location of etm4_release_trace_id. - https://lore.kernel.org/all/20260413142003.3549310-1-yeoreum.yun@arm.com/ from v3 to v4: - change etm_drvdata->spinlock type to raw_spin_lock_t - remove redundant call etmX_enable_hw() with starting_cpu() callsback. - fix missing trace id release. - add missing docs. - https://lore.kernel.org/all/20260412175506.412301-1-yeoreum.yun@arm.com/ from v2 to v3: - fix build error for etm3x. - fix checkpatch warning. - https://lore.kernel.org/all/20260410074310.2693385-1-yeoreum.yun@arm.com/ from v1 to v2 - rebased to v7.0-rc7. - introduce etmX_caps structure to save etmX's capabilities. - remove ss_status from etmv4_config. - modify active_config after taking a mode (perf/sysfs). - https://lore.kernel.org/all/20260317181705.2456271-1-yeoreum.yun@arm.com/ Yeoreum Yun (13): coresight: etm4x: fix wrong check of etm4x_sspcicrn_present() coresight: etm4x: fix underflow for usage of (nrseqstate - 1) coresight: etm4x: introduce struct etm4_caps coresight: etm4x: exclude ss_status from drvdata->config coresight: etm4x: remove s_ex_level from config coresight: etm4x: remove redundant fields in etmv4_save_state coresight: etm4x: fix leaked trace id coresight: etm4x: fix inconsistencies with sysfs configuration coresight: etm4x: missing cscfg_csdev_disable_active_config() in perf enable coresight: etm3x: change drvdata->spinlock type to raw_spin_lock_t coresight: etm3x: introduce struct etm_caps coresight: etm3x: fix inconsistencies with sysfs configuration coresight: etm3x: remove redundant cpu online check on etm_enable_sysfs() drivers/hwtracing/coresight/coresight-etm.h | 46 +- .../coresight/coresight-etm3x-core.c | 96 ++-- .../coresight/coresight-etm3x-sysfs.c | 159 +++--- .../hwtracing/coresight/coresight-etm4x-cfg.c | 5 +- .../coresight/coresight-etm4x-core.c | 454 ++++++++++-------- .../coresight/coresight-etm4x-sysfs.c | 204 ++++---- drivers/hwtracing/coresight/coresight-etm4x.h | 202 ++++---- 7 files changed, 639 insertions(+), 527 deletions(-) -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

1 month, 2 weeks

Re: [PATCH v3] coresight: Fix scheduling while atomic in coresight_cpu_pm_notify()

by Leo Yan

On Fri, Jul 17, 2026 at 12:41:54AM +0300, Mohamed Ayman wrote: [...] > static struct coresight_path *coresight_cpu_get_active_path(enum cs_mode mode) > { > struct coresight_device *source; > - bool is_active = false; > + struct coresight_path *path = NULL; > > - source = coresight_get_percpu_source_ref(smp_processor_id()); > - if (!source) > - return NULL; > - > - if (coresight_get_mode(source) & mode) > - is_active = true; > + guard(raw_spinlock_irqsave)(&coresight_dev_lock); > > - coresight_put_percpu_source_ref(source); > + source = per_cpu(csdev_source, smp_processor_id()); > + if (source && (coresight_get_mode(source) & mode)) > + path = source->path; > > - /* > - * It is expected to run in atomic context or with the CPU lock held for > - * sysfs mode, so it cannot be preempted to disable the path. Here > - * returns the active path pointer without concern that its state may > - * change. Since the build path has taken a reference on the component, > - * the path can be safely used by the caller. > - */ Please keep the comment, as it helps explain why the path pointer can be returned and safely used by the caller. > - return is_active ? source->path : NULL; > + return path; With above update: Reviewed-by: Leo Yan <leo.yan(a)arm.com> Just a thought: we could view this in two stages. 1) The first stage is building the CoreSight path, where we need to ensure the involved modules remain bound while the path is being established. 2) Once the path has been built and the device mode is enabled, we enter the runtime stage. From that point on, observing the device mode as enabled guarantees that the associated data structures can be accessed safely. I would leave this to maintainers for a call in case any concerns on lifetime management.

1 month, 2 weeks

Re: [PATCH v3] coresight: Fix scheduling while atomic in coresight_cpu_pm_notify()

by Leo Yan

On Fri, Jul 17, 2026 at 06:12:01PM +0200, Sebastian Andrzej Siewior wrote: [...] > > The raw spinlock (coresight_dev_lock) serializes access to the per-CPU > > csdev_source pointer. It does not guarantee the lifetime of the source > > or its _parent_ device. coresight_unregister() is not only reached from > > module unload; it can also be called when a driver is unbind, for > > example DT overlay removal or device hotplug/unplug. > > But doesn't coresight_unregister() block on the coresight_dev_lock here? Fair point. coresight_cpu_get_active_path() can safely access the source while holding coresight_dev_lock. Unregistration will be blocked until the access from the CPU PM notifier has finished. > > I think a proper fix needs a clearer lifetime model for an active > > session. E.g., we could consider to call device_link_add() to prevent > > device unbind / unregister, and unlink device when the session is > > finished. Once that is in place, the CPU PM notifier can safely use the > > active path without get_device()/put_device() pair anymore. > > Right. I am also not sure about lifetime of coresight_device::path. coresight_device::path is a runtime pointer that is valid only while the device is enabled. Since both the path and the device mode are updated atomically on the local CPU, observing the device mode as enabled guarantees that the corresponding coresight_device::path is valid. Thanks, Leo

1 month, 2 weeks

[PATCH] perf cs-etm: Avoid truncating AUX buffer sizes to int

by Leo Yan

cs_etm__get_trace() returns an int, but it used to return etmq->buf_len on success. That value comes from auxtrace_buffer::size, which is a size_t. For a large AUX trace block, returning the byte count through an int can overflow and make a valid buffer look like a negative error. The callers do not need the actual byte count from cs_etm__get_trace(). The buffer length is already stored in the etmq->buf_len. The callers only need to distinguish three states: < 0: error = 0: no more AUX buffers > 0: data is available Make cs_etm__get_trace() return 0 for all non-error cases and use etmq->buf_len to indicate whether a new buffer was found. Then make cs_etm__get_data_block() return 1 whenever data is available, instead of returning the buffer length. Also refactor cs_etm__get_data_block() to make its return value semantics clearer. Reported-by: Suyash Mahar <smahar(a)meta.com> Fixes: 8224531cf5a1 ("perf cs-etm: Modularize auxtrace_buffer fetch function") Signed-off-by: Leo Yan <leo.yan(a)arm.com> --- tools/perf/util/cs-etm.c | 46 ++++++++++++++++++++++++++-------------------- 1 file changed, 26 insertions(+), 20 deletions(-) diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index 95e3ec1171acc8442d8539a72a26a1a5a53a2f37..114b3cd2da495e54e78df8fbd707898312f95079 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1467,8 +1467,7 @@ cs_etm__get_trace(struct cs_etm_queue *etmq) etmq->buf_used = 0; etmq->buf_len = aux_buffer->size; etmq->buf = aux_buffer->data; - - return etmq->buf_len; + return 0; } /* @@ -2151,26 +2150,33 @@ static int cs_etm__get_data_block(struct cs_etm_queue *etmq) { int ret; - if (!etmq->buf_len) { - ret = cs_etm__get_trace(etmq); - if (ret <= 0) - return ret; - /* - * We cannot assume consecutive blocks in the data file - * are contiguous, reset the decoder to force re-sync. - */ - ret = cs_etm_decoder__reset(etmq->decoder); - if (ret) - return ret; + /* The current block is not finished */ + if (etmq->buf_len) + return 1; - /* - * Since the decoder is reset, this causes a global trace - * discontinuity. Flush all thread stacks. - */ - cs_etm__flush_all_stack(etmq); - } + ret = cs_etm__get_trace(etmq); + if (ret < 0) + return ret; + + /* No more buffer to read */ + if (!etmq->buf_len) + return 0; + + /* + * We cannot assume consecutive blocks in the data file + * are contiguous, reset the decoder to force re-sync. + */ + ret = cs_etm_decoder__reset(etmq->decoder); + if (ret) + return ret; + + /* + * Since the decoder is reset, this causes a global trace + * discontinuity. Flush all thread stacks. + */ + cs_etm__flush_all_stack(etmq); - return etmq->buf_len; + return 1; } static bool cs_etm__is_svc_instr(struct cs_etm_queue *etmq, --- base-commit: e01c7bd5b1eece254bcbf282db066b12c4815d21 change-id: 20260720-perf_cs_etm_fix_big_size-ec5608f767df Best regards, -- Leo Yan <leo.yan(a)arm.com>

1 month, 2 weeks

Re: [PATCH v2] coresight: dummy: add missing MODULE_DEVICE_TABLE()

by Leo Yan

On Mon, Jul 20, 2026 at 07:45:14PM +0800, Pengpeng Hou wrote: > The CoreSight dummy driver has an OF match table wired into its platform > driver, but does not export the table to module metadata. A modular build > therefore lacks OF aliases for automatic loading. > > Export dummy_match with MODULE_DEVICE_TABLE(). > > Fixes: 9d3ba0b6c056 ("Coresight: Add coresight dummy driver") > Reviewed-by: Jie Gan <jie.gan(a)oss.qualcomm.com> > Signed-off-by: Pengpeng Hou <pengpeng(a)iscas.ac.cn> Reviewed-by: Leo Yan <leo.yan(a)arm.com> > --- > Changes since v1: https://lore.kernel.org/all/20260704121621.48544-1-pengpeng@iscas.ac.cn/ > - add the requested Fixes tag > - carry Jie Gan's conditional Reviewed-by after making that change > - rebase onto v7.2-rc4 > > drivers/hwtracing/coresight/coresight-dummy.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/hwtracing/coresight/coresight-dummy.c b/drivers/hwtracing/coresight/coresight-dummy.c > index c176a2f57300..04880d38feb7 100644 > --- a/drivers/hwtracing/coresight/coresight-dummy.c > +++ b/drivers/hwtracing/coresight/coresight-dummy.c > @@ -212,6 +212,7 @@ static const struct of_device_id dummy_match[] = { > {.compatible = "arm,coresight-dummy-sink"}, > {}, > }; > +MODULE_DEVICE_TABLE(of, dummy_match); > > static struct platform_driver dummy_driver = { > .probe = dummy_probe, >

1 month, 3 weeks

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