From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f72.google.com (mail-pj1-f72.google.com [209.85.216.72]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7C09742B318 for ; Tue, 11 Aug 2026 23:51:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786492279; cv=none; b=PYd6jZsnu0SVxOA+/whOPgOqUg2iJ/ybPa5qTApPfWHbjuzgOk585CuRkhU3hN1S7WzFEtumhwgu7HWablFf9wf7ai7p/u3JrJddm5vzztpE/AVVP4eXIGuddaWCAW8DSffCwbooecDxD4iFWcvUdpIV2AyWj02U8ptr7jKcqmw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786492279; c=relaxed/simple; bh=GXiBqm/G+j3Nh1AQw2KR3rMvjiFbf6Ekr+KtI+I+86Y=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Ce+UmtpcvdGhzbC5R+O7B1QtGJ6RMNsuatvjQWKrDj5jy+QxglgXSI8+rt1m4mf84klQd848A7GOo/HjeWxMQGkesGz+8FO8xJga2rZ1QarPMgs2CYdxe8+IDU1x40k+b7ONw2SM/VuaqC4dDkFUvvDUo2HxzgwYl7SAJafPeF8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--irogers.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=QxvcWj3v; arc=none smtp.client-ip=209.85.216.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--irogers.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QxvcWj3v" Received: by mail-pj1-f72.google.com with SMTP id 98e67ed59e1d1-38f97b3f853so569725a91.3 for ; Tue, 11 Aug 2026 16:51:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786492278; x=1787097078; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=4U5bn9fxWsfK1Zj0iZYwkOob+4cM7Ff/aHIVm3hMKJM=; b=QxvcWj3vcAdJlIHSccMSk09gvVb5oghOn5B4cgov7EQMC7yQWVcaNCL76Mq/GGbBxs uM19092UAc+lsbP85GWeqDLKDBZ6+3xojh/uk+XCgoUABT1zFJDHB3LPia0GIYrs3fAI yos/BrFi1Ij2E1yFpzMcY9ytxqM5e9z9+dZFo9YcTiyyu2Q//mSL6WloYgcDcXN3rrzU 9YEG90xF2s///DSnKrbMH+l9/AT/LVTtWODoNV88ngF/6s8aIToucrshOiva0Sp2aiHI I/kALmUx10mRs/GL3O7JxnoO0KlhcEuI2E+KbElBray4Ph0P48lhpdHIs+g5ese0jOOg elxg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786492278; x=1787097078; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=4U5bn9fxWsfK1Zj0iZYwkOob+4cM7Ff/aHIVm3hMKJM=; b=krs0nM5WjrjlBV5uVa5sHrsc1AJxbNUVrsMjf42lqeX7+fxKoh9zTCblavO8yCx65b SVIsrvoYkZkETJtuOGjxLNFLYVXqqQfH+ttH1G1KI6XxWxPXuFrsAJ6htqgr9TNkigH/ DBDyclxkH/Gbfz5GmBN5/fns4Xu01iC4eq3UALhW3IQRQGTUK4ip7UTnn4KaGpoiGp0q hGRp0PuC3U1S3hZbrtUCM79mtoFJ5JypCx0N/aGzisxfjDWTv8Pd7WMLv4Dvr3K1cklQ XfR5WEiVkj97zrdGXHtN2xCajVpGbNqJDqFxiij/SfBdBao8JQUbx+BPAjabe6Yvoacf URzw== X-Forwarded-Encrypted: i=1; AHgh+RpWdM/vyFDk8aIrjKtH46hzRR23ZC5bvHxnY3B+aUl/pELmrg1nXugQi2ITSk/f3e2zBF+4MGu+/GufSNY=@vger.kernel.org X-Gm-Message-State: AOJu0Yy4MgFdyw0C9NMNWXahB0w3cC9LEje7x5N5wryfp4JI7+qwc9UU 3xbWX89V98YhvlN/GFsEdKseYM1EWaIyTGLTSHse1dJsdVkffYN2yBFNSlMiYKGi/oXy/CyjZaj XSImEzJad1Q== X-Received: from dlbsi7.prod.google.com ([2002:a05:7022:b887:b0:13f:a0ee:666f]) (user=irogers job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:3b81:b0:38d:dfd1:7a8 with SMTP id 98e67ed59e1d1-39301285deamr718924a91.2.1786492277667; Tue, 11 Aug 2026 16:51:17 -0700 (PDT) Date: Tue, 11 Aug 2026 16:51:10 -0700 In-Reply-To: <20260811083828.2057695-1-irogers@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260811083828.2057695-1-irogers@google.com> X-Mailer: git-send-email 2.55.0.679.g6767b8d81c-goog Message-ID: <20260811235112.2267241-1-irogers@google.com> Subject: [PATCH v2 0/2] perf: Add Raspberry Pi AXI PMU driver From: Ian Rogers To: irogers@google.com, linux-perf-users@vger.kernel.org, linux-rpi-kernel@lists.infradead.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, will@kernel.org, "=?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?=" Content-Type: text/plain; charset="UTF-8" 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. Changes in v2 ------------- - Match Data Initialization: In rpi_axi_pmu__init(), set pmu->chip via of_device_get_match_data(dev) to ensure BCM2712 match data is correctly parsed. - Sysfs Event Visibility Filtering: Updated rpi_axi_pmu_events_is_visible() to properly filter all 7 BCM2712 master filtered event aliases (arm_, pcie0_, hvs_filtered, emmc0_) on BCM2835-BCM2711 systems, and hide legacy RPi 1-4 aliases on BCM2712 systems. - Unmapped Monitor Check: Added monitor base_address and initialization check to config_is_valid(). Events targeting uninitialized or unmapped monitors (e.g. missing memory resource or monitor=1 on BCM2712) are properly rejected with -EINVAL. - CPU Affinity Enforcement: Restrict uncore events in event_init() to event->cpu == pmu->cpu to prevent orphaned uncore events when a non-PMU CPU goes offline. - 31-bit Counter Wrap Delta: Mask counter accumulation with delta = (new_count - prev_count) & 0x7FFFFFFF in read(), timer_handler(), and vpu_work_handler() to prevent 2B+ event spikes on counter overflow. - Stopped Event Guard: Return early in rpi_axi_pmu_read() if event->hw.state & PERF_HES_STOPPED. - Lockless Race Fix: Pass bus and filter explicitly to rpi_axi_pmu_enable_bus_watcher() under spinlock to prevent lockless read races in vpu_work_handler(). - Slot Reuse Clean: Set enabled[idx] = false in rpi_axi_pmu_del() when refcount[idx] == 0 so re-allocated watcher slots properly enable hardware watchers. - Events Array Bounds: Return -ENOSPC in rpi_axi_pmu_add() if pmu->events array is full. - Timer Cancel Race Fix: Re-acquire pmu->lock after hrtimer_cancel() in rpi_axi_pmu_del() and re-verify active_events > 0 before returning. - Hotplug Timer Migration: Cancel and re-pin pmu->hrtimer to target CPU in rpi_axi_pmu_offline_cpu(). - Registration Order: Call perf_pmu_register() before cpuhp_state_add_instance() in probe, and cancel hrtimer before cancel_work_sync() and unregister in exit teardown. - Header & Style Cleanups: Removed and , updated rpi_axi_pmu_match[] terminator to { }, and fixed C variable declaration style. 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 | 2001 ++++++++++++++++++++++++++++++++++++ 3 files changed, 2012 insertions(+) create mode 100644 drivers/perf/rpi_axi_pmu.c -- 2.55.0.679.g6767b8d81c-goog