From: Leo Yan <leo.yan@arm.com>
To: James Clark <james.clark@linaro.org>
Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Mike Leach <mike.leach@arm.com>,
Yeoreum Yun <yeoreum.yun@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Will Deacon <will@kernel.org>, Yabin Cui <yabinc@google.com>,
Keita Morisaki <keyz@google.com>,
Yuanfang Zhang <quic_yuanfang@quicinc.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Tamas Petz <tamas.petz@arm.com>,
Thomas Gleixner <tglx@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v10 17/20] coresight: trbe: Save and restore state across CPU low power state
Date: Thu, 9 Apr 2026 16:54:33 +0100 [thread overview]
Message-ID: <20260409155433.GV356832@e132581.arm.com> (raw)
In-Reply-To: <e2241b98-92a6-45e0-a9d3-061f1ed69ae1@linaro.org>
On Thu, Apr 09, 2026 at 11:52:06AM +0100, James Clark wrote:
> On 05/04/2026 4:02 pm, Leo Yan wrote:
> > From: Yabin Cui <yabinc@google.com>
> >
> > TRBE context can be lost when a CPU enters low power states. If a trace
> > source is restored while TRBE is not, tracing may run without an active
> > sink, which can lead to hangs on some devices (e.g., Pixel 9).
>
> Can't this still happen if saving the source times out on "wait for
> TRCSTATR.IDLE to go up"?
>
> That would make coresight_pm_save() exit early, not saving the active TRBE
> state. Then when coresight_pm_restore() is called it restores a stale
> inactive sink, then enables the source again which is the state that can
> hang.
Hmm... I don't expect this to happen anyway.
If CPU PM enter fails and returns an error, it will bail out early of
the idle flow and the CPU will not proceed entering low power states;
therefore, the restore flow does not exist.
Thanks,
Leo
next prev parent reply other threads:[~2026-04-09 15:54 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-05 15:02 [PATCH v10 00/20] CoreSight: Refactor power management for CoreSight path Leo Yan
2026-04-05 15:02 ` [PATCH v10 01/20] coresight: Extract device init into coresight_init_device() Leo Yan
2026-04-05 15:02 ` [PATCH v10 02/20] coresight: Populate CPU ID into coresight_device Leo Yan
2026-04-05 15:02 ` [PATCH v10 03/20] coresight: Remove .cpu_id() callback from source ops Leo Yan
2026-04-05 15:02 ` [PATCH v10 04/20] coresight: Take hotplug lock in enable_source_store() for Sysfs mode Leo Yan
2026-04-05 15:02 ` [PATCH v10 05/20] coresight: etm4x: Set per-CPU path on local CPU Leo Yan
2026-04-05 15:02 ` [PATCH v10 06/20] coresight: etm3x: " Leo Yan
2026-04-05 15:02 ` [PATCH v10 07/20] coresight: Register CPU PM notifier in core layer Leo Yan
2026-04-05 15:02 ` [PATCH v10 08/20] coresight: etm4x: Hook CPU PM callbacks Leo Yan
2026-04-05 15:02 ` [PATCH v10 09/20] coresight: etm4x: Remove redundant checks in PM save and restore Leo Yan
2026-04-05 15:02 ` [PATCH v10 10/20] coresight: syscfg: Use IRQ-safe spinlock to protect active variables Leo Yan
2026-04-05 15:02 ` [PATCH v10 11/20] coresight: Move source helper disabling to coresight_disable_path() Leo Yan
2026-04-05 15:02 ` [PATCH v10 12/20] coresight: Control path with range Leo Yan
2026-04-05 15:02 ` [PATCH v10 13/20] coresight: Use helpers to fetch first and last nodes Leo Yan
2026-04-05 15:02 ` [PATCH v10 14/20] coresight: Introduce coresight_enable_source() helper Leo Yan
2026-04-05 15:02 ` [PATCH v10 15/20] coresight: Control path during CPU idle Leo Yan
2026-04-05 15:02 ` [PATCH v10 16/20] coresight: Add PM callbacks for sink device Leo Yan
2026-04-09 10:52 ` James Clark
2026-04-09 12:54 ` James Clark
2026-04-09 13:14 ` Suzuki K Poulose
2026-04-09 14:30 ` James Clark
2026-04-09 14:31 ` James Clark
2026-04-09 14:49 ` Leo Yan
2026-04-09 15:44 ` Leo Yan
2026-04-05 15:02 ` [PATCH v10 17/20] coresight: trbe: Save and restore state across CPU low power state Leo Yan
2026-04-09 10:52 ` James Clark
2026-04-09 15:54 ` Leo Yan [this message]
2026-04-05 15:02 ` [PATCH v10 18/20] coresight: sysfs: Increment refcount only for system tracers Leo Yan
2026-04-05 15:02 ` [PATCH v10 19/20] coresight: Move CPU hotplug callbacks to core layer Leo Yan
2026-04-05 15:02 ` [PATCH v10 20/20] coresight: sysfs: Validate CPU online status for per-CPU sources Leo Yan
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