Linux Perf Users
 help / color / mirror / Atom feed
* [PATCH v1 0/2] perf: Add Raspberry Pi AXI PMU driver
@ 2026-08-11  8:38 Ian Rogers
  2026-08-11  8:38 ` [PATCH v1 1/2] perf: Add Raspberry Pi BCM2835 " Ian Rogers
  2026-08-11  8:38 ` [PATCH v1 2/2] perf: Add Raspberry Pi 5 (BCM2712) AXI PMU support Ian Rogers
  0 siblings, 2 replies; 4+ messages in thread
From: Ian Rogers @ 2026-08-11  8:38 UTC (permalink / raw)
  To: Will Deacon, Mark Rutland, linux-kernel, linux-arm-kernel,
	linux-perf-users, linux-rpi-kernel
  Cc: Ian Rogers

This patch series adds an uncore Performance Monitoring Unit (PMU) driver
for Broadcom AXI system and VideoCore VPU performance monitors found on
Raspberry Pi SoCs (BCM2835 through BCM2712 / Raspberry Pi 1 through 5).

Motivation & Background
------------------------
Currently, Linux lacks a standard perf-API compatible driver for the
Broadcom AXI performance counter blocks on Raspberry Pi platforms. Prior
out-of-tree vendor solutions relied on custom debugfs nodes and ad-hoc
kthreads, preventing integration with standard Linux perf tooling (`perf stat`,
`perf list`, etc.).

This driver implements standard `struct pmu` hardware uncore callbacks
under `drivers/perf/`, exposing human-readable sysfs event aliases, unit
scaling (`Bytes`), and bus filtering directly to user space.

Key Architectural Improvements & Features
------------------------------------------
1. Standard Linux Perf Integration:
   - Exposes uncore AXI interconnect events via `/sys/bus/event_source/devices/rpi_axi_pmu/`.
   - Supports event sampling and hardware counter accumulation (`local64_add`),
     automatically managing 31-bit hardware counter wraparound across high-bandwidth
     interconnect transfers.

2. CPU Hotplug Support (`cpuhp`):
   - Registers dynamic CPU hotplug notifiers (`CPUHP_AP_ONLINE_DYN`).
   - Automatically migrates PMU context (`perf_pmu_migrate_context`) to an online
     CPU core when a designated CPU goes offline, avoiding stale uncore state.

3. Hybrid Memory-Mapped & Mailbox Work Queue Architecture:
   - System Monitor (MMIO): Performs fast atomic-safe memory reads (~15ns)
     directly mapped over ARM physical memory space (`MON__SYSTEM`).
   - VPU Monitor (Mailbox IPC): For Broadcom BCM2835-BCM2711 platforms (RPi 1-4),
     VideoCore VPU monitor IPC calls are offloaded to process context via a dedicated
     workqueue (`vpu_work`) and serialized under `vpu_mutex`. This avoids atomic
     sleeps or blocking in timer/interrupt context.

4. SoC Generation Support:
   - Patch 1 adds core driver support for Broadcom BCM2835-BCM2711 (RPi 1-4).
   - Patch 2 expands support for Broadcom BCM2712 (Raspberry Pi 5), adding PCIe RP1
     Southbridge links, HEVC decoder, HVS display engine, and Cortex-A76 DSU L3
     interconnect monitoring.

Hardware Validation
-------------------
The driver has been validated on real hardware across multiple SoC generations:
- Raspberry Pi 400 (BCM2711): Validated System L2, ARM CPU, and VideoCore VPU
  firmware mailbox IPC performance counters.
- Raspberry Pi 5 (BCM2712): Validated live byte throughput across HVS display
  refresh cycles, Cortex-A76 DSU L3 interconnect memory traffic, and PCIe RP1
  Southbridge transfers.

Ian Rogers (2):
  perf: Add Raspberry Pi BCM2835 AXI PMU driver
  perf: Add Raspberry Pi 5 (BCM2712) AXI PMU support

 drivers/perf/Kconfig       |   10 +
 drivers/perf/Makefile      |    1 +
 drivers/perf/rpi_axi_pmu.c | 1948 ++++++++++++++++++++++++++++++++++++
 3 files changed, 1959 insertions(+)
 create mode 100644 drivers/perf/rpi_axi_pmu.c

-- 
2.55.0.679.g6767b8d81c-goog


^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2026-08-11 14:32 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-08-11  8:38 [PATCH v1 0/2] perf: Add Raspberry Pi AXI PMU driver Ian Rogers
2026-08-11  8:38 ` [PATCH v1 1/2] perf: Add Raspberry Pi BCM2835 " Ian Rogers
2026-08-11 14:32   ` Uwe Kleine-König
2026-08-11  8:38 ` [PATCH v1 2/2] perf: Add Raspberry Pi 5 (BCM2712) AXI PMU support Ian Rogers

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox