Messages in this thread |  | | Date | Sat, 14 Nov 2020 13:17:15 +0800 | From | Tingwei Zhang <> | Subject | Re: [RFC 00/11] arm64: coresight: Enable ETE and TRBE |
| |
Hi Anshuman,
On Tue, Nov 10, 2020 at 08:44:58PM +0800, Anshuman Khandual wrote: > This series enables future IP trace features Embedded Trace Extension (ETE) > and Trace Buffer Extension (TRBE). This series depends on the ETM system > register instruction support series [0] and the v8.4 Self hosted tracing > support series (Jonathan Zhou) [1]. The tree is available here [2] for > quick access. > > ETE is the PE (CPU) trace unit for CPUs, implementing future architecture > extensions. ETE overlaps with the ETMv4 architecture, with additions to > support the newer architecture features and some restrictions on the > supported features w.r.t ETMv4. The ETE support is added by extending the > ETMv4 driver to recognise the ETE and handle the features as exposed by the > TRCIDRx registers. ETE only supports system instructions access from the > host CPU. The ETE could be integrated with a TRBE (see below), or with the > legacy CoreSight trace bus (e.g, ETRs). Thus the ETE follows same firmware > description as the ETMs and requires a node per instance. > > Trace Buffer Extensions (TRBE) implements a per CPU trace buffer, which is > accessible via the system registers and can be combined with the ETE to > provide a 1x1 configuration of source & sink. TRBE is being represented > here as a CoreSight sink. Primary reason is that the ETE source could work > with other traditional CoreSight sink devices. As TRBE captures the trace > data which is produced by ETE, it cannot work alone. > > TRBE representation here have some distinct deviations from a traditional > CoreSight sink device. Coresight path between ETE and TRBE are not built > during boot looking at respective DT or ACPI entries. Instead TRBE gets > checked on each available CPU, when found gets connected with respective > ETE source device on the same CPU, after altering its outward connections. > ETE TRBE path connection lasts only till the CPU is online. But ETE-TRBE > coupling/decoupling method implemented here is not optimal and would be > reworked later on.
Only perf mode is supported in TRBE in current path. Will you consider support sysfs mode as well in following patch sets?
Thanks, Tingwei
> > Unlike traditional sinks, TRBE can generate interrupts to signal including > many other things, buffer got filled. The interrupt is a PPI and should be > communicated from the platform. DT or ACPI entry representing TRBE should > have the PPI number for a given platform. During perf session, the TRBE IRQ > handler should capture trace for perf auxiliary buffer before restarting it > back. System registers being used here to configure ETE and TRBE could be > referred in the link below. > > https://developer.arm.com/docs/ddi0601/g/aarch64-system-registers. > > This adds another change where CoreSight sink device needs to be disabled > before capturing the trace data for perf in order to avoid race condition > with another simultaneous TRBE IRQ handling. This might cause problem with > traditional sink devices which can be operated in both sysfs and perf mode. > This needs to be addressed correctly. One option would be to move the > update_buffer callback into the respective sink devices. e.g, disable(). > > This series is primarily looking from some early feed back both on proposed > design and its implementation. It acknowledges, that it might be incomplete > and will have scopes for improvement. > > Things todo: > - Improve ETE-TRBE coupling and decoupling method > - Improve TRBE IRQ handling for all possible corner cases > - Implement sysfs based trace sessions > > [0] > https://lore.kernel.org/linux-arm-kernel/20201028220945.3826358-1-suzuki.poulose@arm.com/ > [1] > https://lore.kernel.org/linux-arm-kernel/1600396210-54196-1-git-send-email-jonathan.zhouwen@huawei.com/ > [2] > https://gitlab.arm.com/linux-arm/linux-skp/-/tree/coresight/etm/v8.4-self-hosted > > Anshuman Khandual (6): > arm64: Add TRBE definitions > coresight: sink: Add TRBE driver > coresight: etm-perf: Truncate the perf record if handle has no space > coresight: etm-perf: Disable the path before capturing the trace data > coresgith: etm-perf: Connect TRBE sink with ETE source > dts: bindings: Document device tree binding for Arm TRBE > > Suzuki K Poulose (5): > coresight: etm-perf: Allow an event to use different sinks > coresight: Do not scan for graph if none is present > coresight: etm4x: Add support for PE OS lock > coresight: ete: Add support for sysreg support > coresight: ete: Detect ETE as one of the supported ETMs > > .../devicetree/bindings/arm/coresight.txt | 3 + > Documentation/devicetree/bindings/arm/trbe.txt | 20 + > Documentation/trace/coresight/coresight-trbe.rst | 36 + > arch/arm64/include/asm/sysreg.h | 51 ++ > drivers/hwtracing/coresight/Kconfig | 11 + > drivers/hwtracing/coresight/Makefile | 1 + > drivers/hwtracing/coresight/coresight-etm-perf.c | 85 ++- > drivers/hwtracing/coresight/coresight-etm-perf.h | 4 + > drivers/hwtracing/coresight/coresight-etm4x-core.c | 144 +++- > drivers/hwtracing/coresight/coresight-etm4x.h | 64 +- > drivers/hwtracing/coresight/coresight-platform.c | 9 +- > drivers/hwtracing/coresight/coresight-trbe.c | 768 > +++++++++++++++++++++ > drivers/hwtracing/coresight/coresight-trbe.h | 525 ++++++++++++++ > include/linux/coresight.h | 2 + > 14 files changed, 1680 insertions(+), 43 deletions(-) > create mode 100644 Documentation/devicetree/bindings/arm/trbe.txt > create mode 100644 Documentation/trace/coresight/coresight-trbe.rst > create mode 100644 drivers/hwtracing/coresight/coresight-trbe.c > create mode 100644 drivers/hwtracing/coresight/coresight-trbe.h > > -- > 2.7.4 > > _______________________________________________ > CoreSight mailing list > CoreSight@lists.linaro.org > https://lists.linaro.org/mailman/listinfo/coresight
|  |