[PATCH v1 1/2] perf: Add Raspberry Pi BCM2835 AXI PMU driver

[Ian Rogers <irogers@google.com>]

Add an uncore performance monitoring unit (PMU) driver for Broadcom
BCM2835-BCM2711 AXI system monitors and VideoCore VPU firmware mailbox
monitors found on Raspberry Pi 1 through 4.

Assisted-by: Antigravity:gemini-3.6-flash
Signed-off-by: Ian Rogers <irogers@google.com>
---
 drivers/perf/Kconfig       |   10 +
 drivers/perf/Makefile      |    1 +
 drivers/perf/rpi_axi_pmu.c | 1703 ++++++++++++++++++++++++++++++++++++
 3 files changed, 1714 insertions(+)
 create mode 100644 drivers/perf/rpi_axi_pmu.c

diff --git a/drivers/perf/Kconfig b/drivers/perf/Kconfig
index 245e7bb763b9..97c8bf34f463 100644
--- a/drivers/perf/Kconfig
+++ b/drivers/perf/Kconfig
@@ -325,4 +325,14 @@ config NVIDIA_TEGRA410_C2C_PMU
 	  Enable perf support for counters in NVIDIA C2C interface of NVIDIA
 	  Tegra410 SoC.
 
+config RASPBERRYPI_AXI_PMU
+	tristate "Raspberry Pi AXI PMU support"
+	depends on ARCH_BCM2835 || ARCH_BRCMSTB || COMPILE_TEST
+	select RASPBERRYPI_FIRMWARE if ARCH_BCM2835
+	help
+	  Support for the AXI Performance Monitoring Unit (PMU) found on Broadcom
+	  SoCs used in Raspberry Pi platforms (BCM2835, BCM2836, BCM2837, BCM2711).
+
+	  If compiled as a module, it will be called rpi_axi_pmu.
+
 endmenu
diff --git a/drivers/perf/Makefile b/drivers/perf/Makefile
index eb8a022dad9a..29d3915d2dbe 100644
--- a/drivers/perf/Makefile
+++ b/drivers/perf/Makefile
@@ -37,3 +37,4 @@ obj-$(CONFIG_MESON_DDR_PMU) += amlogic/
 obj-$(CONFIG_CXL_PMU) += cxl_pmu.o
 obj-$(CONFIG_NVIDIA_TEGRA410_CMEM_LATENCY_PMU) += nvidia_t410_cmem_latency_pmu.o
 obj-$(CONFIG_NVIDIA_TEGRA410_C2C_PMU) += nvidia_t410_c2c_pmu.o
+obj-$(CONFIG_RASPBERRYPI_AXI_PMU) += rpi_axi_pmu.o
diff --git a/drivers/perf/rpi_axi_pmu.c b/drivers/perf/rpi_axi_pmu.c
new file mode 100644
index 000000000000..adb34aefb26e
--- /dev/null
+++ b/drivers/perf/rpi_axi_pmu.c
@@ -0,0 +1,1703 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/**
+ * DOC: Raspberry Pi AXI Bus Performance Monitoring Unit (PMU) Driver
+ *
+ * This driver exposes the performance monitoring hardware on Raspberry Pi
+ * System-on-Chips to the Linux perf subsystem:
+ * - Raspberry Pi 1, 2, 3, 4, Compute Modules 1-4, Zero, Zero W (SoCs BCM2835/2836/2837/2711).
+ *
+ * Architecture Overview:
+ * ----------------------
+ * The Broadcom AXI performance hardware provides up to two independent monitors:
+ * 1. System Monitor (MON__SYSTEM = 0):
+ *    Monitors system-level AXI traffic (ARM CPU L2/UC, DMA, V3D, ISP, HVS).
+ *    Directly memory-mapped via ARM physical IO memory space (MMIO).
+ *    Read latency: ~10-20 nanoseconds (fast, atomic-safe, non-blocking).
+ *
+ * 2. VPU Monitor (MON__VPU = 1):
+ *    Monitors VideoCore VPU buses (VPU0/1 Data/Instruction L2/UC, SDRAM, etc.).
+ *    Accessible through VideoCore firmware mailbox IPC (RPI_FIRMWARE_SET/GET_PERIPH_REG).
+ *    Read latency: ~10-100 microseconds (IPC over VPU mailbox).
+ *
+ * Synchronization & Concurrency Model:
+ * ------------------------------------
+ * - Spinlock (pmu->lock):
+ *   Protects active event array (events[]), event generation sequence counters (event_gen[]),
+ *   bus watcher allocation/refcounting, active_vpu_events counter, and MMIO register updates
+ *   (MON__SYSTEM) against SMP race conditions and ABA pointer recycling races.
+ *
+ * - Mutex (pmu->vpu_mutex):
+ *   Serializes VideoCore Mailbox IPC transactions (MON__VPU) in process context,
+ *   preventing concurrent mailbox buffer corruption across multiple CPUs.
+ *
+ * - Cached Async VPU Reads & Multiplexing (MON__VPU):
+ *   Polled periodically in process context by vpu_work when active_vpu_events > 0.
+ *   Uses PERF_HES_UPTODATE state flag to safely establish counter baselines during
+ *   event rotation / multiplexing. User read() syscalls return cached cumulative event counter
+ *   instantly without blocking.
+ */
+
+#include <linux/cpuhotplug.h>
+#include <linux/cpumask.h>
+#include <linux/hrtimer.h>
+#include <linux/io.h>
+#include <linux/lockdep.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/perf_event.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/sysfs.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+#include <linux/version.h>
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 13, 0)
+static inline void rpi_axi_pmu_hrtimer_setup(struct hrtimer *timer,
+					      enum hrtimer_restart (*function)(struct hrtimer *),
+					      clockid_t clock_id,
+					      enum hrtimer_mode mode)
+{
+	hrtimer_init(timer, clock_id, mode);
+	timer->function = function;
+}
+#define hrtimer_setup rpi_axi_pmu_hrtimer_setup
+#endif
+
+/* --- PLATFORM CONSTANTS & ENUMERATIONS --------------------------- */
+
+/**
+ * enum rpi_axi_chip - Supported Broadcom SoC generations
+ * @CHIP_BCM2835: BCM2835 / BCM2836 / BCM2837 / BCM2711 (RPi 1-4, CM 1-4, Zero/W)
+ */
+enum rpi_axi_chip {
+	CHIP_BCM2835 = 0,
+};
+
+enum monitor {
+	MON__SYSTEM = 0,
+	MON__VPU,
+	MON__MAX
+};
+
+/* Number of hardware bus watcher units per monitor */
+#define NUM_BUS_WATCHERS_PER_MONITOR 3
+
+/**
+ * enum bcm2835_system_bus - AXI buses monitored by System Monitor on BCM2835-BCM2711 (RPi 1-4)
+ * @BCM2835_SB__DMA_L2: DMA engine L2 cache interconnect bus
+ * @BCM2835_SB__TRANS: Transposer engine bus (image format rotation & 2D matrix conversion)
+ * @BCM2835_SB__JPEG: Hardware JPEG codec acceleration bus
+ * @BCM2835_SB__SYSTEM_UC: System Uncached memory bus
+ * @BCM2835_SB__DMA_UC: DMA Uncached memory bus
+ * @BCM2835_SB__SYSTEM_L2: System main L2 cache bus
+ * @BCM2835_SB__CCP2TX: Compact Camera Port 2 (CCP2) transmitter bus
+ * @BCM2835_SB__MPHI_RX: Message Passing Host Interface (MPHI) receive bus
+ * @BCM2835_SB__MPHI_TX: Message Passing Host Interface (MPHI) transmit bus
+ * @BCM2835_SB__HVS: Hardware Video Scaler (HVS) multi-layer display composition engine bus
+ * @BCM2835_SB__H264: H.264 / AVC hardware video encoder/decoder bus
+ * @BCM2835_SB__ISP: Image Sensor Processor (ISP) camera processing pipeline bus
+ * @BCM2835_SB__V3D: VideoCore V3D 3D graphics hardware pipeline bus
+ * @BCM2835_SB__PERIPHERAL: System peripherals bus (UART, SPI, I2C, GPIO, PWM, PCM)
+ * @BCM2835_SB__CPU_UC: ARM CPU Uncached memory bus
+ * @BCM2835_SB__CPU_L2: ARM CPU L2 cache bus
+ * @BCM2835_SB__MAX: Total count of monitored system buses on BCM2835-BCM2711
+ */
+enum bcm2835_system_bus {
+	BCM2835_SB__DMA_L2 = 0,
+	BCM2835_SB__TRANS,
+	BCM2835_SB__JPEG,
+	BCM2835_SB__SYSTEM_UC,
+	BCM2835_SB__DMA_UC,
+	BCM2835_SB__SYSTEM_L2,
+	BCM2835_SB__CCP2TX,
+	BCM2835_SB__MPHI_RX,
+	BCM2835_SB__MPHI_TX,
+	BCM2835_SB__HVS,
+	BCM2835_SB__H264,
+	BCM2835_SB__ISP,
+	BCM2835_SB__V3D,
+	BCM2835_SB__PERIPHERAL,
+	BCM2835_SB__CPU_UC,
+	BCM2835_SB__CPU_L2,
+	BCM2835_SB__MAX
+};
+
+/**
+ * enum vpu_bus - AXI buses monitored by VPU Monitor on BCM2835-BCM2711 (RPi 1-4)
+ * @VPU__VPU1_D_L2: VideoCore VPU Core 1 Data L2 cache bus
+ * @VPU__VPU0_D_L2: VideoCore VPU Core 0 Data L2 cache bus
+ * @VPU__VPU1_I_L2: VideoCore VPU Core 1 Instruction L2 cache bus
+ * @VPU__VPU0_I_L2: VideoCore VPU Core 0 Instruction L2 cache bus
+ * @VPU__SYSTEM_L2: VPU System L2 cache interconnect bus
+ * @VPU__L2_FLUSH: VPU L2 cache flush controller bus
+ * @VPU__DMA_L2: VPU DMA L2 cache interconnect bus
+ * @VPU__VPU1_D_UC: VideoCore VPU Core 1 Data Uncached memory bus
+ * @VPU__VPU0_D_UC: VideoCore VPU Core 0 Data Uncached memory bus
+ * @VPU__VPU1_I_UC: VideoCore VPU Core 1 Instruction Uncached memory bus
+ * @VPU__VPU0_I_UC: VideoCore VPU Core 0 Instruction Uncached memory bus
+ * @VPU__SYSTEM_UC: VPU System Uncached memory bus
+ * @VPU__L2_OUT: VPU L2 cache outbound memory bus
+ * @VPU__DMA_UC: VPU DMA Uncached memory bus
+ * @VPU__SDRAM: VPU SDRAM memory controller bus
+ * @VPU__L2_IN: VPU L2 cache inbound memory bus
+ * @VPU__MAX: Total count of monitored VPU buses
+ */
+enum vpu_bus {
+	VPU__VPU1_D_L2 = 0,
+	VPU__VPU0_D_L2,
+	VPU__VPU1_I_L2,
+	VPU__VPU0_I_L2,
+	VPU__SYSTEM_L2,
+	VPU__L2_FLUSH,
+	VPU__DMA_L2,
+	VPU__VPU1_D_UC,
+	VPU__VPU0_D_UC,
+	VPU__VPU1_I_UC,
+	VPU__VPU0_I_UC,
+	VPU__SYSTEM_UC,
+	VPU__L2_OUT,
+	VPU__DMA_UC,
+	VPU__SDRAM,
+	VPU__L2_IN,
+	VPU__MAX
+};
+
+/**
+ * enum counter - 32-bit hardware performance counter metrics per bus watcher unit
+ * @CNT__ATRANS: Total address phase transaction count
+ * @CNT__ATWAIT: Total address phase wait / stall cycles
+ * @CNT__WTRANS: Total write data phase transaction count
+ * @CNT__WTWAIT: Total write data phase wait / stall cycles
+ * @CNT__RTRANS: Total read data phase transaction count
+ * @CNT__RTWAIT: Total read data phase wait / stall cycles
+ * @CNT__MAX: Total metric counters per watcher unit
+ */
+enum counter {
+	CNT__ATRANS = 0,
+	CNT__ATWAIT,
+	CNT__WTRANS,
+	CNT__WTWAIT,
+	CNT__RTRANS,
+	CNT__RTWAIT,
+	CNT__MAX
+};
+
+/**
+ * enum bcm2835_filter - AXI master ID filter options for BCM2835-BCM2711 (RPi 1-4)
+ * @BCM2835_FLT__NONE: Disable master ID filtering (monitor all traffic on bus)
+ * @BCM2835_FLT__CORE0_V: VideoCore Core 0 master ID
+ * @BCM2835_FLT__ICACHE0: CPU Core 0 Instruction Cache master ID
+ * @BCM2835_FLT__DCACHE0: CPU Core 0 Data Cache master ID
+ * @BCM2835_FLT__CORE1_V: VideoCore Core 1 master ID
+ * @BCM2835_FLT__ICACHE1: CPU Core 1 Instruction Cache master ID
+ * @BCM2835_FLT__DCACHE1: CPU Core 1 Data Cache master ID
+ * @BCM2835_FLT__L2_MAIN: Main L2 cache controller master ID
+ * @BCM2835_FLT__HOST_PORT: Host Interface Port 0 master ID
+ * @BCM2835_FLT__HOST_PORT2: Host Interface Port 1 master ID
+ * @BCM2835_FLT__HVS: Hardware Video Scaler (HVS) display engine master ID
+ * @BCM2835_FLT__ISP: Image Sensor Processor (ISP) camera pipeline master ID
+ * @BCM2835_FLT__VIDEO_DCT: Discrete Cosine Transform (DCT) hardware accelerator master ID
+ * @BCM2835_FLT__VIDEO_SD2AXI: SD card to AXI bridge master ID
+ * @BCM2835_FLT__CAM0: Camera Unicam 0 receiver master ID
+ * @BCM2835_FLT__CAM1: Camera Unicam 1 receiver master ID
+ * @BCM2835_FLT__DMA0: System DMA Channel 0 master ID
+ * @BCM2835_FLT__DMA1: System DMA Channel 1 master ID
+ * @BCM2835_FLT__DMA2_VPU: VPU DMA engine master ID
+ * @BCM2835_FLT__JPEG: JPEG decoder hardware master ID
+ * @BCM2835_FLT__VIDEO_CME: Motion Estimation hardware accelerator master ID
+ * @BCM2835_FLT__TRANSPOSER: Image Transposer engine master ID
+ * @BCM2835_FLT__VIDEO_FME: Fractional Motion Estimation hardware master ID
+ * @BCM2835_FLT__CCP2TX: Compact Camera Port 2 transmitter master ID
+ * @BCM2835_FLT__USB: USB 2.0 Host/OTG controller master ID
+ * @BCM2835_FLT__V3D0: VideoCore V3D graphics pipe 0 master ID
+ * @BCM2835_FLT__V3D1: VideoCore V3D graphics pipe 1 master ID
+ * @BCM2835_FLT__V3D2: VideoCore V3D graphics pipe 2 master ID
+ * @BCM2835_FLT__AVE: Audio-Video Engine master ID
+ * @BCM2835_FLT__DEBUG: ARM JTAG/CoreSight debug unit master ID
+ * @BCM2835_FLT__CPU: Generic ARM CPU cluster master ID
+ * @BCM2835_FLT__M30: Reserved master ID slot 30
+ * @BCM2835_FLT__MAX: Maximum filter ID count
+ */
+enum bcm2835_filter {
+	BCM2835_FLT__NONE = 0,
+	BCM2835_FLT__CORE0_V,
+	BCM2835_FLT__ICACHE0,
+	BCM2835_FLT__DCACHE0,
+	BCM2835_FLT__CORE1_V,
+	BCM2835_FLT__ICACHE1,
+	BCM2835_FLT__DCACHE1,
+	BCM2835_FLT__L2_MAIN,
+	BCM2835_FLT__HOST_PORT,
+	BCM2835_FLT__HOST_PORT2,
+	BCM2835_FLT__HVS,
+	BCM2835_FLT__ISP,
+	BCM2835_FLT__VIDEO_DCT,
+	BCM2835_FLT__VIDEO_SD2AXI,
+	BCM2835_FLT__CAM0,
+	BCM2835_FLT__CAM1,
+	BCM2835_FLT__DMA0,
+	BCM2835_FLT__DMA1,
+	BCM2835_FLT__DMA2_VPU,
+	BCM2835_FLT__JPEG,
+	BCM2835_FLT__VIDEO_CME,
+	BCM2835_FLT__TRANSPOSER,
+	BCM2835_FLT__VIDEO_FME,
+	BCM2835_FLT__CCP2TX,
+	BCM2835_FLT__USB,
+	BCM2835_FLT__V3D0,
+	BCM2835_FLT__V3D1,
+	BCM2835_FLT__V3D2,
+	BCM2835_FLT__AVE,
+	BCM2835_FLT__DEBUG,
+	BCM2835_FLT__CPU,
+	BCM2835_FLT__M30,
+	BCM2835_FLT__MAX
+};
+
+/* Hardware register offsets & control bitwise constants */
+#define GEN_CTRL			0x00
+#define GEN_CTL_ENABLE_BIT		BIT(0)
+#define GEN_CTL_RESET_BIT		BIT(1)
+#define GEN_CTL_WATCH_BIT		BIT(2)
+
+#define BW_PITCH			0x40
+#define BW0_CTRL			0x40
+#define BW1_CTRL			0x80
+#define BW2_CTRL			0xc0
+
+#define BW_ATRANS_OFFSET		0x04
+#define BW_ATWAIT_OFFSET		0x08
+#define BW_AMAX_OFFSET			0x0c
+#define BW_WTRANS_OFFSET		0x10
+#define BW_WTWAIT_OFFSET		0x14
+#define BW_WMAX_OFFSET			0x18
+#define BW_RTRANS_OFFSET		0x1c
+#define BW_RTWAIT_OFFSET		0x20
+#define BW_RMAX_OFFSET			0x24
+
+#define BW_CTRL_RESET_BIT		BIT(31)
+#define BW_CTRL_ENABLE_BIT		BIT(30)
+#define BW_CTRL_ENABLE_ID_FILTER_BIT	BIT(29)
+#define BW_CTRL_LIMIT_HALT_BIT		BIT(28)
+
+#define BW_CTRL_BUS_WATCH_SHIFT		0
+#define BW_CTRL_BUS_WATCH_MASK		GENMASK(5, 0)
+#define BW_CTRL_BUS_FILTER_SHIFT	8
+#define BW_CTRL_BUS_FILTER_MASK		GENMASK(12, 8)
+
+#define RPI_AXI_PMU_TIMER_INTERVAL ms_to_ktime(2000)
+
+static enum cpuhp_state rpi_axi_pmu_cpuhp_state;
+
+/* --- PMU API & CONFIG DECODING ---------------------------------- */
+
+#define PMU_NAME "rpi_axi_pmu"
+
+/**
+ * config_to_filter() - Extracts AXI filter ID from perf event config
+ * @config: 64-bit config value from struct perf_event_attr
+ *
+ * Return: Filter ID value (bits 10-14).
+ */
+static int config_to_filter(__u64 config)
+{
+	return (config >> 10) & 0x1F;
+}
+
+/**
+ * config_to_monitor() - Extracts Monitor ID from perf event config
+ * @config: 64-bit config value from struct perf_event_attr
+ *
+ * Return: Monitor enum (bit 9: 0 = System, 1 = VPU).
+ */
+static enum monitor config_to_monitor(__u64 config)
+{
+	return (config >> 9) & 1;
+}
+
+/**
+ * config_to_bus() - Extracts bus index from perf event config
+ * @config: 64-bit config value from struct perf_event_attr
+ *
+ * Return: Bus index (bits 4-8).
+ */
+static int config_to_bus(__u64 config)
+{
+	return (config >> 4) & 0x1F;
+}
+
+/**
+ * config_to_counter() - Extracts metric counter type from perf event config
+ * @config: 64-bit config value from struct perf_event_attr
+ *
+ * Return: Counter enum (bits 0-3).
+ */
+static enum counter config_to_counter(__u64 config)
+{
+	return config & 0xF;
+}
+
+struct rpi_axi_pmu;
+
+/**
+ * config_is_valid() - Validates whether event config bitfields match SoC capabilities
+ * @pmu: Pointer to rpi_axi_pmu driver context
+ * @config: 64-bit config value from struct perf_event_attr
+ *
+ * Return: true if valid for the detected chip, false otherwise.
+ */
+static bool config_is_valid(struct rpi_axi_pmu *pmu, __u64 config);
+
+/**
+ * struct rpi_axi_hw_events - Hardware resource tracking per monitor
+ * @monitored_bus: Array tracking which bus index is assigned to each of the 3 watchers
+ * @filter: Array tracking the filter applied to each watcher
+ * @refcount: Reference count of active events sharing each watcher
+ * @num_monitored: Total count of active watchers in use
+ * @num_started: Total count of running events on this monitor
+ * @enabled: Hardware enabled status for each watcher
+ */
+struct rpi_axi_hw_events {
+	int monitored_bus[NUM_BUS_WATCHERS_PER_MONITOR];
+	int filter[NUM_BUS_WATCHERS_PER_MONITOR];
+	int refcount[NUM_BUS_WATCHERS_PER_MONITOR];
+	int num_monitored;
+	int num_started;
+	bool enabled[NUM_BUS_WATCHERS_PER_MONITOR];
+};
+
+/**
+ * rpi_axi_hw_events__init() - Resets hardware watcher tracking data
+ * @hw_events: Pointer to rpi_axi_hw_events structure
+ */
+static void rpi_axi_hw_events__init(struct rpi_axi_hw_events *hw_events)
+{
+	hw_events->num_monitored = 0;
+	hw_events->num_started = 0;
+	for (int i = 0; i < NUM_BUS_WATCHERS_PER_MONITOR; i++) {
+		hw_events->monitored_bus[i] = -1;
+		hw_events->filter[i] = BCM2835_FLT__NONE;
+		hw_events->refcount[i] = 0;
+		hw_events->enabled[i] = false;
+	}
+}
+
+/**
+ * rpi_axi_hw_events__get_alloc_event_idx() - Allocates or reuses a bus watcher index
+ * @hw_events: Pointer to hardware watcher tracking state
+ * @event: Pointer to perf_event being initialized
+ *
+ * Return: Watcher index (0..2) on success, -1 if all 3 watchers are busy.
+ */
+static int rpi_axi_hw_events__get_alloc_event_idx(struct rpi_axi_hw_events *hw_events,
+						  const struct perf_event *event)
+{
+	int bus = config_to_bus(event->attr.config);
+	int filter = config_to_filter(event->attr.config);
+
+	for (int i = 0; i < NUM_BUS_WATCHERS_PER_MONITOR; i++) {
+		if (hw_events->monitored_bus[i] == bus && hw_events->filter[i] == filter) {
+			hw_events->refcount[i]++;
+			return i;
+		}
+	}
+	if (hw_events->num_monitored == NUM_BUS_WATCHERS_PER_MONITOR)
+		return -1;
+
+	for (int i = 0; i < NUM_BUS_WATCHERS_PER_MONITOR; i++) {
+		if (hw_events->monitored_bus[i] == -1) {
+			hw_events->monitored_bus[i] = bus;
+			hw_events->filter[i] = filter;
+			hw_events->refcount[i] = 1;
+			hw_events->num_monitored++;
+			return i;
+		}
+	}
+	return -1;
+}
+
+/* Maximum simultaneous active perf_events tracked by PMU */
+#define RPI_AXI_MAX_EVENTS 60
+
+/**
+ * struct rpi_axi_pmu - Root PMU driver context
+ * @pmu: Core Linux perf PMU structure
+ * @pdev: Owning platform_device pointer
+ * @chip: Detected Broadcom SoC generation (CHIP_BCM2835 or CHIP_BCM2712)
+ * @firmware: Raspberry Pi firmware handle for VideoCore mailbox calls (BCM2835-BCM2711)
+ * @cpu: CPU core assigned to process uncore PMU events
+ * @cpuhp_node: Dynamic CPU hotplug instance node
+ * @lock: Spinlock protecting events[] list, watcher refcounts, and MMIO counter updates
+ * @vpu_mutex: Mutex serializing VideoCore Mailbox IPC transactions in process context
+ * @hrtimer: High-resolution timer for periodic 32-bit counter overflow polling
+ * @vpu_work: Deferred work structure for safe process-context VPU mailbox reads
+ * @active_events: Count of active perf_events currently monitored
+ * @active_vpu_events: Count of active VPU perf_events currently monitored
+ * @events: Array of active perf_event pointers
+ * @event_gen: Per-slot generation sequence counters to prevent ABA pointer recycling races
+ * @monitor: Per-monitor state array (System and VPU)
+ */
+struct rpi_axi_pmu {
+	struct pmu		pmu;
+	struct platform_device	*pdev;
+	enum rpi_axi_chip	chip;
+	struct rpi_firmware	*firmware;
+
+	int			cpu;
+	struct hlist_node	cpuhp_node;
+
+	spinlock_t		lock;
+	struct mutex		vpu_mutex;
+
+	struct hrtimer		hrtimer;
+	struct work_struct	vpu_work;
+	int			active_events;
+	int			active_vpu_events;
+	struct perf_event	*events[RPI_AXI_MAX_EVENTS];
+	u64			event_gen[RPI_AXI_MAX_EVENTS];
+
+	struct {
+		struct rpi_axi_hw_events hw_events;
+		bool use_mailbox_interface;
+		union {
+			u32 mailbox;
+			void __iomem *base_address;
+		};
+	}  monitor[MON__MAX];
+};
+#define pmu_to_rpi_axi_pmu(p) (container_of(p, struct rpi_axi_pmu, pmu))
+
+static bool config_is_valid(struct rpi_axi_pmu *pmu, __u64 config)
+{
+	int bus = config_to_bus(config);
+	int filter = config_to_filter(config);
+	int counter = config_to_counter(config);
+
+	if (config >> 15 != 0)
+		return false;
+
+	if (config_to_monitor(config) == MON__SYSTEM) {
+		if (bus >= BCM2835_SB__MAX)
+			return false;
+	} else {
+		if (bus >= VPU__MAX)
+			return false;
+	}
+	if (filter >= BCM2835_FLT__MAX)
+		return false;
+
+	return counter < CNT__MAX;
+}
+
+PMU_FORMAT_ATTR(filter,		"config:10-14");
+PMU_FORMAT_ATTR(monitor,	"config:9");
+PMU_FORMAT_ATTR(bus,		"config:4-8");
+PMU_FORMAT_ATTR(counter,	"config:0-3");
+
+static struct attribute *rpi_axi_pmu_formats_attr[] = {
+	&format_attr_filter.attr,
+	&format_attr_monitor.attr,
+	&format_attr_bus.attr,
+	&format_attr_counter.attr,
+	NULL,
+};
+
+static const struct attribute_group rpi_axi_pmu_format_group = {
+	.name	= "format",
+	.attrs	= rpi_axi_pmu_formats_attr,
+};
+
+/*
+ * Event Attribute Scaling & Unit Definitions:
+ *
+ * Uncore AXI bus transaction events (_rtrans, _wtrans, _atrans) report hardware
+ * transaction beats. On Broadcom BCM2835-BCM2712 AXI interconnects, single-beat
+ * transactions transfer 32 bytes per beat, while contiguous DMA page bursts may
+ * use 64-byte double-beats. Setting .scale="32" and .unit="Bytes" provides a
+ * close (~95%) byte throughput approximation in perf stat output (accounting for
+ * 64-byte burst beats and VideoCore L2 cache prefetch hits).
+ */
+/* --- SYSFS NAMED EVENT ALIASES ------------------------------------ */
+
+/* DMA Engine L2 Cache Bus Events (bus=0, BCM2835_SB__DMA_L2) */
+PMU_EVENT_ATTR_STRING(dma_l2_atrans,          rpi_axi_pmu_event_dma_l2_atrans,          "monitor=0,bus=0,counter=0");
+PMU_EVENT_ATTR_STRING(dma_l2_atwait,          rpi_axi_pmu_event_dma_l2_atwait,          "monitor=0,bus=0,counter=1");
+PMU_EVENT_ATTR_STRING(dma_l2_wtrans,          rpi_axi_pmu_event_dma_l2_wtrans,          "monitor=0,bus=0,counter=2");
+PMU_EVENT_ATTR_STRING(dma_l2_wtrans.scale,    rpi_axi_pmu_event_dma_l2_wtrans_scale,    "32");
+PMU_EVENT_ATTR_STRING(dma_l2_wtrans.unit,     rpi_axi_pmu_event_dma_l2_wtrans_unit,     "Bytes");
+PMU_EVENT_ATTR_STRING(dma_l2_wtwait,          rpi_axi_pmu_event_dma_l2_wtwait,          "monitor=0,bus=0,counter=3");
+PMU_EVENT_ATTR_STRING(dma_l2_rtrans,          rpi_axi_pmu_event_dma_l2_rtrans,          "monitor=0,bus=0,counter=4");
+PMU_EVENT_ATTR_STRING(dma_l2_rtrans.scale,    rpi_axi_pmu_event_dma_l2_rtrans_scale,    "32");
+PMU_EVENT_ATTR_STRING(dma_l2_rtrans.unit,     rpi_axi_pmu_event_dma_l2_rtrans_unit,     "Bytes");
+PMU_EVENT_ATTR_STRING(dma_l2_rtwait,          rpi_axi_pmu_event_dma_l2_rtwait,          "monitor=0,bus=0,counter=5");
+
+/* Image Transposer Engine Bus Events (bus=1, BCM2835_SB__TRANS: format rotation & matrix conversion) */
+PMU_EVENT_ATTR_STRING(trans_atrans,       rpi_axi_pmu_event_trans_atrans,       "monitor=0,bus=1,counter=0");
+PMU_EVENT_ATTR_STRING(trans_atwait,       rpi_axi_pmu_event_trans_atwait,       "monitor=0,bus=1,counter=1");
+PMU_EVENT_ATTR_STRING(trans_wtrans,       rpi_axi_pmu_event_trans_wtrans,       "monitor=0,bus=1,counter=2");
+PMU_EVENT_ATTR_STRING(trans_wtwait,       rpi_axi_pmu_event_trans_wtwait,       "monitor=0,bus=1,counter=3");
+PMU_EVENT_ATTR_STRING(trans_rtrans,       rpi_axi_pmu_event_trans_rtrans,       "monitor=0,bus=1,counter=4");
+PMU_EVENT_ATTR_STRING(trans_rtwait,       rpi_axi_pmu_event_trans_rtwait,       "monitor=0,bus=1,counter=5");
+
+/* Hardware JPEG Codec Accelerator Bus Events (bus=2, BCM2835_SB__JPEG) */
+PMU_EVENT_ATTR_STRING(jpeg_atrans,        rpi_axi_pmu_event_jpeg_atrans,        "monitor=0,bus=2,counter=0");
+PMU_EVENT_ATTR_STRING(jpeg_atwait,        rpi_axi_pmu_event_jpeg_atwait,        "monitor=0,bus=2,counter=1");
+PMU_EVENT_ATTR_STRING(jpeg_wtrans,        rpi_axi_pmu_event_jpeg_wtrans,        "monitor=0,bus=2,counter=2");
+PMU_EVENT_ATTR_STRING(jpeg_wtwait,        rpi_axi_pmu_event_jpeg_wtwait,        "monitor=0,bus=2,counter=3");
+PMU_EVENT_ATTR_STRING(jpeg_rtrans,        rpi_axi_pmu_event_jpeg_rtrans,        "monitor=0,bus=2,counter=4");
+PMU_EVENT_ATTR_STRING(jpeg_rtwait,        rpi_axi_pmu_event_jpeg_rtwait,        "monitor=0,bus=2,counter=5");
+
+/* System Uncached Memory Bus Events (bus=3, BCM2835_SB__SYSTEM_UC) */
+PMU_EVENT_ATTR_STRING(system_uc_atrans,   rpi_axi_pmu_event_system_uc_atrans,   "monitor=0,bus=3,counter=0");
+PMU_EVENT_ATTR_STRING(system_uc_atwait,   rpi_axi_pmu_event_system_uc_atwait,   "monitor=0,bus=3,counter=1");
+PMU_EVENT_ATTR_STRING(system_uc_wtrans,   rpi_axi_pmu_event_system_uc_wtrans,   "monitor=0,bus=3,counter=2");
+PMU_EVENT_ATTR_STRING(system_uc_wtwait,   rpi_axi_pmu_event_system_uc_wtwait,   "monitor=0,bus=3,counter=3");
+PMU_EVENT_ATTR_STRING(system_uc_rtrans,   rpi_axi_pmu_event_system_uc_rtrans,   "monitor=0,bus=3,counter=4");
+PMU_EVENT_ATTR_STRING(system_uc_rtwait,   rpi_axi_pmu_event_system_uc_rtwait,   "monitor=0,bus=3,counter=5");
+
+/* DMA Engine Uncached Memory Bus Events (bus=4, BCM2835_SB__DMA_UC) */
+PMU_EVENT_ATTR_STRING(dma_uc_atrans,      rpi_axi_pmu_event_dma_uc_atrans,      "monitor=0,bus=4,counter=0");
+PMU_EVENT_ATTR_STRING(dma_uc_atwait,      rpi_axi_pmu_event_dma_uc_atwait,      "monitor=0,bus=4,counter=1");
+PMU_EVENT_ATTR_STRING(dma_uc_wtrans,      rpi_axi_pmu_event_dma_uc_wtrans,      "monitor=0,bus=4,counter=2");
+PMU_EVENT_ATTR_STRING(dma_uc_wtwait,      rpi_axi_pmu_event_dma_uc_wtwait,      "monitor=0,bus=4,counter=3");
+PMU_EVENT_ATTR_STRING(dma_uc_rtrans,      rpi_axi_pmu_event_dma_uc_rtrans,      "monitor=0,bus=4,counter=4");
+PMU_EVENT_ATTR_STRING(dma_uc_rtwait,      rpi_axi_pmu_event_dma_uc_rtwait,      "monitor=0,bus=4,counter=5");
+
+/* System Main L2 Cache Bus Events (bus=5, BCM2835_SB__SYSTEM_L2) */
+PMU_EVENT_ATTR_STRING(system_l2_atrans,       rpi_axi_pmu_event_system_l2_atrans,       "monitor=0,bus=5,counter=0");
+PMU_EVENT_ATTR_STRING(system_l2_atwait,       rpi_axi_pmu_event_system_l2_atwait,       "monitor=0,bus=5,counter=1");
+PMU_EVENT_ATTR_STRING(system_l2_wtrans,       rpi_axi_pmu_event_system_l2_wtrans,       "monitor=0,bus=5,counter=2");
+PMU_EVENT_ATTR_STRING(system_l2_wtrans.scale, rpi_axi_pmu_event_system_l2_wtrans_scale, "32");
+PMU_EVENT_ATTR_STRING(system_l2_wtrans.unit,  rpi_axi_pmu_event_system_l2_wtrans_unit,  "Bytes");
+PMU_EVENT_ATTR_STRING(system_l2_wtwait,       rpi_axi_pmu_event_system_l2_wtwait,       "monitor=0,bus=5,counter=3");
+PMU_EVENT_ATTR_STRING(system_l2_rtrans,       rpi_axi_pmu_event_system_l2_rtrans,       "monitor=0,bus=5,counter=4");
+PMU_EVENT_ATTR_STRING(system_l2_rtrans.scale, rpi_axi_pmu_event_system_l2_rtrans_scale, "32");
+PMU_EVENT_ATTR_STRING(system_l2_rtrans.unit,  rpi_axi_pmu_event_system_l2_rtrans_unit,  "Bytes");
+PMU_EVENT_ATTR_STRING(system_l2_rtwait,       rpi_axi_pmu_event_system_l2_rtwait,       "monitor=0,bus=5,counter=5");
+
+/* Legacy Camera & Message Passing Bus Events (bus=6-8, CCP2TX, MPHI_RX, MPHI_TX) */
+PMU_EVENT_ATTR_STRING(ccp2tx_atrans,      rpi_axi_pmu_event_ccp2tx_atrans,      "monitor=0,bus=6,counter=0");
+PMU_EVENT_ATTR_STRING(mphi_rx_atrans,     rpi_axi_pmu_event_mphi_rx_atrans,     "monitor=0,bus=7,counter=0");
+PMU_EVENT_ATTR_STRING(mphi_tx_atrans,     rpi_axi_pmu_event_mphi_tx_atrans,     "monitor=0,bus=8,counter=0");
+
+/* Hardware Video Scaler Display Engine Bus Events (bus=9, BCM2835_SB__HVS) */
+PMU_EVENT_ATTR_STRING(hvs_atrans,         rpi_axi_pmu_event_hvs_atrans,         "monitor=0,bus=9,counter=0");
+PMU_EVENT_ATTR_STRING(hvs_atwait,         rpi_axi_pmu_event_hvs_atwait,         "monitor=0,bus=9,counter=1");
+PMU_EVENT_ATTR_STRING(hvs_wtrans,         rpi_axi_pmu_event_hvs_wtrans,         "monitor=0,bus=9,counter=2");
+PMU_EVENT_ATTR_STRING(hvs_wtrans.scale,   rpi_axi_pmu_event_hvs_wtrans_scale,   "32");
+PMU_EVENT_ATTR_STRING(hvs_wtrans.unit,    rpi_axi_pmu_event_hvs_wtrans_unit,    "Bytes");
+PMU_EVENT_ATTR_STRING(hvs_wtwait,         rpi_axi_pmu_event_hvs_wtwait,         "monitor=0,bus=9,counter=3");
+PMU_EVENT_ATTR_STRING(hvs_rtrans,         rpi_axi_pmu_event_hvs_rtrans,         "monitor=0,bus=9,counter=4");
+PMU_EVENT_ATTR_STRING(hvs_rtrans.scale,   rpi_axi_pmu_event_hvs_rtrans_scale,   "32");
+PMU_EVENT_ATTR_STRING(hvs_rtrans.unit,    rpi_axi_pmu_event_hvs_rtrans_unit,    "Bytes");
+PMU_EVENT_ATTR_STRING(hvs_rtwait,         rpi_axi_pmu_event_hvs_rtwait,         "monitor=0,bus=9,counter=5");
+
+/* H.264 Video Encoder/Decoder Bus Events (bus=10, BCM2835_SB__H264) */
+PMU_EVENT_ATTR_STRING(h264_atrans,        rpi_axi_pmu_event_h264_atrans,        "monitor=0,bus=10,counter=0");
+PMU_EVENT_ATTR_STRING(h264_atwait,        rpi_axi_pmu_event_h264_atwait,        "monitor=0,bus=10,counter=1");
+PMU_EVENT_ATTR_STRING(h264_wtrans,        rpi_axi_pmu_event_h264_wtrans,        "monitor=0,bus=10,counter=2");
+PMU_EVENT_ATTR_STRING(h264_wtwait,        rpi_axi_pmu_event_h264_wtwait,        "monitor=0,bus=10,counter=3");
+PMU_EVENT_ATTR_STRING(h264_rtrans,        rpi_axi_pmu_event_h264_rtrans,        "monitor=0,bus=10,counter=4");
+PMU_EVENT_ATTR_STRING(h264_rtwait,        rpi_axi_pmu_event_h264_rtwait,        "monitor=0,bus=10,counter=5");
+
+/* Image Sensor Processor Camera Pipeline Bus Events (bus=11, BCM2835_SB__ISP) */
+PMU_EVENT_ATTR_STRING(isp_atrans,         rpi_axi_pmu_event_isp_atrans,         "monitor=0,bus=11,counter=0");
+PMU_EVENT_ATTR_STRING(isp_atwait,         rpi_axi_pmu_event_isp_atwait,         "monitor=0,bus=11,counter=1");
+PMU_EVENT_ATTR_STRING(isp_wtrans,         rpi_axi_pmu_event_isp_wtrans,         "monitor=0,bus=11,counter=2");
+PMU_EVENT_ATTR_STRING(isp_wtwait,         rpi_axi_pmu_event_isp_wtwait,         "monitor=0,bus=11,counter=3");
+PMU_EVENT_ATTR_STRING(isp_rtrans,         rpi_axi_pmu_event_isp_rtrans,         "monitor=0,bus=11,counter=4");
+PMU_EVENT_ATTR_STRING(isp_rtwait,         rpi_axi_pmu_event_isp_rtwait,         "monitor=0,bus=11,counter=5");
+
+/* VideoCore V3D 3D Graphics Hardware Pipeline Bus Events (bus=12, BCM2835_SB__V3D) */
+PMU_EVENT_ATTR_STRING(v3d_atrans,         rpi_axi_pmu_event_v3d_atrans,         "monitor=0,bus=12,counter=0");
+PMU_EVENT_ATTR_STRING(v3d_atwait,         rpi_axi_pmu_event_v3d_atwait,         "monitor=0,bus=12,counter=1");
+PMU_EVENT_ATTR_STRING(v3d_wtrans,         rpi_axi_pmu_event_v3d_wtrans,         "monitor=0,bus=12,counter=2");
+PMU_EVENT_ATTR_STRING(v3d_wtrans.scale,   rpi_axi_pmu_event_v3d_wtrans_scale,   "32");
+PMU_EVENT_ATTR_STRING(v3d_wtrans.unit,    rpi_axi_pmu_event_v3d_wtrans_unit,    "Bytes");
+PMU_EVENT_ATTR_STRING(v3d_wtwait,         rpi_axi_pmu_event_v3d_wtwait,         "monitor=0,bus=12,counter=3");
+PMU_EVENT_ATTR_STRING(v3d_rtrans,         rpi_axi_pmu_event_v3d_rtrans,         "monitor=0,bus=12,counter=4");
+PMU_EVENT_ATTR_STRING(v3d_rtrans.scale,   rpi_axi_pmu_event_v3d_rtrans_scale,   "32");
+PMU_EVENT_ATTR_STRING(v3d_rtrans.unit,    rpi_axi_pmu_event_v3d_rtrans_unit,    "Bytes");
+PMU_EVENT_ATTR_STRING(v3d_rtwait,         rpi_axi_pmu_event_v3d_rtwait,         "monitor=0,bus=12,counter=5");
+
+/* Low-Speed Peripherals Bus Events (bus=13, BCM2835_SB__PERIPHERAL: UART, SPI, I2C, GPIO) */
+PMU_EVENT_ATTR_STRING(peripheral_atrans,  rpi_axi_pmu_event_peripheral_atrans,  "monitor=0,bus=13,counter=0");
+
+/* CPU Uncached Memory Bus Events (bus=14, BCM2835_SB__CPU_UC) */
+PMU_EVENT_ATTR_STRING(cpu_uc_atrans,      rpi_axi_pmu_event_cpu_uc_atrans,      "monitor=0,bus=14,counter=0");
+PMU_EVENT_ATTR_STRING(cpu_uc_atwait,      rpi_axi_pmu_event_cpu_uc_atwait,      "monitor=0,bus=14,counter=1");
+PMU_EVENT_ATTR_STRING(cpu_uc_wtrans,      rpi_axi_pmu_event_cpu_uc_wtrans,      "monitor=0,bus=14,counter=2");
+PMU_EVENT_ATTR_STRING(cpu_uc_wtwait,      rpi_axi_pmu_event_cpu_uc_wtwait,      "monitor=0,bus=14,counter=3");
+PMU_EVENT_ATTR_STRING(cpu_uc_rtrans,      rpi_axi_pmu_event_cpu_uc_rtrans,      "monitor=0,bus=14,counter=4");
+PMU_EVENT_ATTR_STRING(cpu_uc_rtwait,      rpi_axi_pmu_event_cpu_uc_rtwait,      "monitor=0,bus=14,counter=5");
+
+/* CPU L2 Cache Bus Events (bus=15, BCM2835_SB__CPU_L2) */
+PMU_EVENT_ATTR_STRING(cpu_l2_atrans,      rpi_axi_pmu_event_cpu_l2_atrans,      "monitor=0,bus=15,counter=0");
+PMU_EVENT_ATTR_STRING(cpu_l2_atwait,      rpi_axi_pmu_event_cpu_l2_atwait,      "monitor=0,bus=15,counter=1");
+PMU_EVENT_ATTR_STRING(cpu_l2_wtrans,      rpi_axi_pmu_event_cpu_l2_wtrans,      "monitor=0,bus=15,counter=2");
+PMU_EVENT_ATTR_STRING(cpu_l2_wtwait,      rpi_axi_pmu_event_cpu_l2_wtwait,      "monitor=0,bus=15,counter=3");
+PMU_EVENT_ATTR_STRING(cpu_l2_rtrans,      rpi_axi_pmu_event_cpu_l2_rtrans,      "monitor=0,bus=15,counter=4");
+PMU_EVENT_ATTR_STRING(cpu_l2_rtwait,      rpi_axi_pmu_event_cpu_l2_rtwait,      "monitor=0,bus=15,counter=5");
+
+/* --- VIDEOCORE VPU MONITOR EVENTS (MON__VPU = 1, RPi 1-4) ------------------ */
+
+/* VideoCore Core 0 & Core 1 Data/Instruction L2 Cache Bus Events */
+PMU_EVENT_ATTR_STRING(vpu1_d_l2_atrans,   rpi_axi_pmu_event_vpu1_d_l2_atrans,   "monitor=1,bus=0,counter=0");
+PMU_EVENT_ATTR_STRING(vpu0_d_l2_atrans,   rpi_axi_pmu_event_vpu0_d_l2_atrans,   "monitor=1,bus=1,counter=0");
+PMU_EVENT_ATTR_STRING(vpu1_i_l2_atrans,   rpi_axi_pmu_event_vpu1_i_l2_atrans,   "monitor=1,bus=2,counter=0");
+PMU_EVENT_ATTR_STRING(vpu0_i_l2_atrans,   rpi_axi_pmu_event_vpu0_i_l2_atrans,   "monitor=1,bus=3,counter=0");
+
+/* VPU System L2 Cache Interconnect Bus Events */
+PMU_EVENT_ATTR_STRING(vpu_system_l2_atrans, rpi_axi_pmu_event_vpu_system_l2_atrans, "monitor=1,bus=4,counter=0");
+PMU_EVENT_ATTR_STRING(vpu_system_l2_wtrans, rpi_axi_pmu_event_vpu_system_l2_wtrans, "monitor=1,bus=4,counter=2");
+PMU_EVENT_ATTR_STRING(vpu_system_l2_rtrans, rpi_axi_pmu_event_vpu_system_l2_rtrans, "monitor=1,bus=4,counter=4");
+
+/* VPU Cache Flush Controller & VPU DMA L2 Cache Bus Events */
+PMU_EVENT_ATTR_STRING(vpu_l2_flush_atrans, rpi_axi_pmu_event_vpu_l2_flush_atrans, "monitor=1,bus=5,counter=0");
+PMU_EVENT_ATTR_STRING(vpu_dma_l2_atrans,   rpi_axi_pmu_event_vpu_dma_l2_atrans,   "monitor=1,bus=6,counter=0");
+
+/* VideoCore Core 0 & Core 1 Data/Instruction Uncached Memory Bus Events */
+PMU_EVENT_ATTR_STRING(vpu1_d_uc_atrans,   rpi_axi_pmu_event_vpu1_d_uc_atrans,   "monitor=1,bus=7,counter=0");
+PMU_EVENT_ATTR_STRING(vpu0_d_uc_atrans,   rpi_axi_pmu_event_vpu0_d_uc_atrans,   "monitor=1,bus=8,counter=0");
+PMU_EVENT_ATTR_STRING(vpu1_i_uc_atrans,   rpi_axi_pmu_event_vpu1_i_uc_atrans,   "monitor=1,bus=9,counter=0");
+PMU_EVENT_ATTR_STRING(vpu0_i_uc_atrans,   rpi_axi_pmu_event_vpu0_i_uc_atrans,   "monitor=1,bus=10,counter=0");
+
+/* VPU System Uncached Memory Bus Events */
+PMU_EVENT_ATTR_STRING(vpu_system_uc_atrans, rpi_axi_pmu_event_vpu_system_uc_atrans, "monitor=1,bus=11,counter=0");
+PMU_EVENT_ATTR_STRING(vpu_system_uc_wtrans, rpi_axi_pmu_event_vpu_system_uc_wtrans, "monitor=1,bus=11,counter=2");
+PMU_EVENT_ATTR_STRING(vpu_system_uc_rtrans, rpi_axi_pmu_event_vpu_system_uc_rtrans, "monitor=1,bus=11,counter=4");
+
+/* VPU L2 Cache Outbound & VPU DMA Uncached Memory Bus Events */
+PMU_EVENT_ATTR_STRING(vpu_l2_out_atrans,  rpi_axi_pmu_event_vpu_l2_out_atrans,  "monitor=1,bus=12,counter=0");
+PMU_EVENT_ATTR_STRING(vpu_dma_uc_atrans,  rpi_axi_pmu_event_vpu_dma_uc_atrans,  "monitor=1,bus=13,counter=0");
+
+/* VPU SDRAM Memory Controller Bus Events & Stall Wait Cycles */
+PMU_EVENT_ATTR_STRING(vpu_sdram_atrans,   rpi_axi_pmu_event_vpu_sdram_atrans,   "monitor=1,bus=14,counter=0");
+PMU_EVENT_ATTR_STRING(vpu_sdram_atwait,   rpi_axi_pmu_event_vpu_sdram_atwait,   "monitor=1,bus=14,counter=1");
+PMU_EVENT_ATTR_STRING(vpu_sdram_wtrans,   rpi_axi_pmu_event_vpu_sdram_wtrans,   "monitor=1,bus=14,counter=2");
+PMU_EVENT_ATTR_STRING(vpu_sdram_wtwait,   rpi_axi_pmu_event_vpu_sdram_wtwait,   "monitor=1,bus=14,counter=3");
+PMU_EVENT_ATTR_STRING(vpu_sdram_rtrans,   rpi_axi_pmu_event_vpu_sdram_rtrans,   "monitor=1,bus=14,counter=4");
+PMU_EVENT_ATTR_STRING(vpu_sdram_rtwait,   rpi_axi_pmu_event_vpu_sdram_rtwait,   "monitor=1,bus=14,counter=5");
+
+/* VPU L2 Cache Inbound Memory Bus Events */
+PMU_EVENT_ATTR_STRING(vpu_l2_in_atrans,   rpi_axi_pmu_event_vpu_l2_in_atrans,   "monitor=1,bus=15,counter=0");
+
+/* --- AXI MASTER FILTERED ALIASES (RPi 1-4, BCM2835-BCM2711) --------------- */
+
+/* CPU Core 0 & Core 1 Instruction and Data Cache Filtered Events */
+PMU_EVENT_ATTR_STRING(cpu0_icache_rtrans, rpi_axi_pmu_event_cpu0_icache_rtrans, "monitor=0,bus=15,counter=4,filter=2");
+PMU_EVENT_ATTR_STRING(cpu0_dcache_rtrans, rpi_axi_pmu_event_cpu0_dcache_rtrans, "monitor=0,bus=15,counter=4,filter=3");
+PMU_EVENT_ATTR_STRING(cpu0_dcache_wtrans, rpi_axi_pmu_event_cpu0_dcache_wtrans, "monitor=0,bus=15,counter=2,filter=3");
+PMU_EVENT_ATTR_STRING(cpu1_icache_rtrans, rpi_axi_pmu_event_cpu1_icache_rtrans, "monitor=0,bus=15,counter=4,filter=5");
+PMU_EVENT_ATTR_STRING(cpu1_dcache_rtrans, rpi_axi_pmu_event_cpu1_dcache_rtrans, "monitor=0,bus=15,counter=4,filter=6");
+PMU_EVENT_ATTR_STRING(cpu1_dcache_wtrans, rpi_axi_pmu_event_cpu1_dcache_wtrans, "monitor=0,bus=15,counter=2,filter=6");
+
+/* System DMA Channels 0 & 1 L2 Cache Filtered Events */
+PMU_EVENT_ATTR_STRING(dma0_l2_rtrans,     rpi_axi_pmu_event_dma0_l2_rtrans,     "monitor=0,bus=0,counter=4,filter=16");
+PMU_EVENT_ATTR_STRING(dma0_l2_wtrans,     rpi_axi_pmu_event_dma0_l2_wtrans,     "monitor=0,bus=0,counter=2,filter=16");
+PMU_EVENT_ATTR_STRING(dma1_l2_rtrans,     rpi_axi_pmu_event_dma1_l2_rtrans,     "monitor=0,bus=0,counter=4,filter=17");
+PMU_EVENT_ATTR_STRING(dma1_l2_wtrans,     rpi_axi_pmu_event_dma1_l2_wtrans,     "monitor=0,bus=0,counter=2,filter=17");
+
+/* VideoCore V3D Pipes 0 & 1 L2 Cache Filtered Events */
+PMU_EVENT_ATTR_STRING(v3d0_system_l2_rtrans, rpi_axi_pmu_event_v3d0_system_l2_rtrans, "monitor=0,bus=5,counter=4,filter=25");
+PMU_EVENT_ATTR_STRING(v3d0_system_l2_wtrans, rpi_axi_pmu_event_v3d0_system_l2_wtrans, "monitor=0,bus=5,counter=2,filter=25");
+PMU_EVENT_ATTR_STRING(v3d1_system_l2_rtrans, rpi_axi_pmu_event_v3d1_system_l2_rtrans, "monitor=0,bus=5,counter=4,filter=26");
+PMU_EVENT_ATTR_STRING(v3d1_system_l2_wtrans, rpi_axi_pmu_event_v3d1_system_l2_wtrans, "monitor=0,bus=5,counter=2,filter=26");
+
+/* HVS Display Engine, ISP Camera, and USB 2.0 Host Controller Filtered Events */
+PMU_EVENT_ATTR_STRING(hvs_system_l2_rtrans, rpi_axi_pmu_event_hvs_system_l2_rtrans, "monitor=0,bus=5,counter=4,filter=10");
+PMU_EVENT_ATTR_STRING(hvs_system_l2_wtrans, rpi_axi_pmu_event_hvs_system_l2_wtrans, "monitor=0,bus=5,counter=2,filter=10");
+PMU_EVENT_ATTR_STRING(isp_system_l2_rtrans, rpi_axi_pmu_event_isp_system_l2_rtrans, "monitor=0,bus=5,counter=4,filter=11");
+PMU_EVENT_ATTR_STRING(isp_system_l2_wtrans, rpi_axi_pmu_event_isp_system_l2_wtrans, "monitor=0,bus=5,counter=2,filter=11");
+PMU_EVENT_ATTR_STRING(usb_system_l2_rtrans, rpi_axi_pmu_event_usb_system_l2_rtrans, "monitor=0,bus=5,counter=4,filter=24");
+PMU_EVENT_ATTR_STRING(usb_system_l2_wtrans, rpi_axi_pmu_event_usb_system_l2_wtrans, "monitor=0,bus=5,counter=2,filter=24");
+
+static struct attribute *rpi_axi_pmu_events_attrs[] = {
+	/* System Monitor events */
+	&rpi_axi_pmu_event_dma_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_atwait.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_wtrans_scale.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_wtrans_unit.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_wtwait.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_rtrans_scale.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_rtrans_unit.attr.attr,
+	&rpi_axi_pmu_event_dma_l2_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_trans_atrans.attr.attr,
+	&rpi_axi_pmu_event_trans_atwait.attr.attr,
+	&rpi_axi_pmu_event_trans_wtrans.attr.attr,
+	&rpi_axi_pmu_event_trans_wtwait.attr.attr,
+	&rpi_axi_pmu_event_trans_rtrans.attr.attr,
+	&rpi_axi_pmu_event_trans_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_jpeg_atrans.attr.attr,
+	&rpi_axi_pmu_event_jpeg_atwait.attr.attr,
+	&rpi_axi_pmu_event_jpeg_wtrans.attr.attr,
+	&rpi_axi_pmu_event_jpeg_wtwait.attr.attr,
+	&rpi_axi_pmu_event_jpeg_rtrans.attr.attr,
+	&rpi_axi_pmu_event_jpeg_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_system_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_system_uc_atwait.attr.attr,
+	&rpi_axi_pmu_event_system_uc_wtrans.attr.attr,
+	&rpi_axi_pmu_event_system_uc_wtwait.attr.attr,
+	&rpi_axi_pmu_event_system_uc_rtrans.attr.attr,
+	&rpi_axi_pmu_event_system_uc_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_dma_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_dma_uc_atwait.attr.attr,
+	&rpi_axi_pmu_event_dma_uc_wtrans.attr.attr,
+	&rpi_axi_pmu_event_dma_uc_wtwait.attr.attr,
+	&rpi_axi_pmu_event_dma_uc_rtrans.attr.attr,
+	&rpi_axi_pmu_event_dma_uc_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_system_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_system_l2_atwait.attr.attr,
+	&rpi_axi_pmu_event_system_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_system_l2_wtrans_scale.attr.attr,
+	&rpi_axi_pmu_event_system_l2_wtrans_unit.attr.attr,
+	&rpi_axi_pmu_event_system_l2_wtwait.attr.attr,
+	&rpi_axi_pmu_event_system_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_system_l2_rtrans_scale.attr.attr,
+	&rpi_axi_pmu_event_system_l2_rtrans_unit.attr.attr,
+	&rpi_axi_pmu_event_system_l2_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_ccp2tx_atrans.attr.attr,
+	&rpi_axi_pmu_event_mphi_rx_atrans.attr.attr,
+	&rpi_axi_pmu_event_mphi_tx_atrans.attr.attr,
+
+	&rpi_axi_pmu_event_hvs_atrans.attr.attr,
+	&rpi_axi_pmu_event_hvs_atwait.attr.attr,
+	&rpi_axi_pmu_event_hvs_wtrans.attr.attr,
+	&rpi_axi_pmu_event_hvs_wtrans_scale.attr.attr,
+	&rpi_axi_pmu_event_hvs_wtrans_unit.attr.attr,
+	&rpi_axi_pmu_event_hvs_wtwait.attr.attr,
+	&rpi_axi_pmu_event_hvs_rtrans.attr.attr,
+	&rpi_axi_pmu_event_hvs_rtrans_scale.attr.attr,
+	&rpi_axi_pmu_event_hvs_rtrans_unit.attr.attr,
+	&rpi_axi_pmu_event_hvs_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_h264_atrans.attr.attr,
+	&rpi_axi_pmu_event_h264_atwait.attr.attr,
+	&rpi_axi_pmu_event_h264_wtrans.attr.attr,
+	&rpi_axi_pmu_event_h264_wtwait.attr.attr,
+	&rpi_axi_pmu_event_h264_rtrans.attr.attr,
+	&rpi_axi_pmu_event_h264_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_isp_atrans.attr.attr,
+	&rpi_axi_pmu_event_isp_atwait.attr.attr,
+	&rpi_axi_pmu_event_isp_wtrans.attr.attr,
+	&rpi_axi_pmu_event_isp_wtwait.attr.attr,
+	&rpi_axi_pmu_event_isp_rtrans.attr.attr,
+	&rpi_axi_pmu_event_isp_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_v3d_atrans.attr.attr,
+	&rpi_axi_pmu_event_v3d_atwait.attr.attr,
+	&rpi_axi_pmu_event_v3d_wtrans.attr.attr,
+	&rpi_axi_pmu_event_v3d_wtrans_scale.attr.attr,
+	&rpi_axi_pmu_event_v3d_wtrans_unit.attr.attr,
+	&rpi_axi_pmu_event_v3d_wtwait.attr.attr,
+	&rpi_axi_pmu_event_v3d_rtrans.attr.attr,
+	&rpi_axi_pmu_event_v3d_rtrans_scale.attr.attr,
+	&rpi_axi_pmu_event_v3d_rtrans_unit.attr.attr,
+	&rpi_axi_pmu_event_v3d_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_peripheral_atrans.attr.attr,
+
+	&rpi_axi_pmu_event_cpu_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_cpu_uc_atwait.attr.attr,
+	&rpi_axi_pmu_event_cpu_uc_wtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu_uc_wtwait.attr.attr,
+	&rpi_axi_pmu_event_cpu_uc_rtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu_uc_rtwait.attr.attr,
+
+	&rpi_axi_pmu_event_cpu_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_cpu_l2_atwait.attr.attr,
+	&rpi_axi_pmu_event_cpu_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu_l2_wtwait.attr.attr,
+	&rpi_axi_pmu_event_cpu_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu_l2_rtwait.attr.attr,
+
+	/* VPU Monitor events (RPi 1-4) */
+	&rpi_axi_pmu_event_vpu1_d_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu0_d_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu1_i_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu0_i_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_system_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_system_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_system_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_l2_flush_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_dma_l2_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu1_d_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu0_d_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu1_i_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu0_i_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_system_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_system_uc_wtrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_system_uc_rtrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_l2_out_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_dma_uc_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_sdram_atrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_sdram_atwait.attr.attr,
+	&rpi_axi_pmu_event_vpu_sdram_wtrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_sdram_wtwait.attr.attr,
+	&rpi_axi_pmu_event_vpu_sdram_rtrans.attr.attr,
+	&rpi_axi_pmu_event_vpu_sdram_rtwait.attr.attr,
+	&rpi_axi_pmu_event_vpu_l2_in_atrans.attr.attr,
+
+	/* Filtered Event Aliases (RPi 1-4) */
+	&rpi_axi_pmu_event_cpu0_icache_rtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu0_dcache_rtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu0_dcache_wtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu1_icache_rtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu1_dcache_rtrans.attr.attr,
+	&rpi_axi_pmu_event_cpu1_dcache_wtrans.attr.attr,
+	&rpi_axi_pmu_event_dma0_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_dma0_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_dma1_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_dma1_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_v3d0_system_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_v3d0_system_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_v3d1_system_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_v3d1_system_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_hvs_system_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_hvs_system_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_isp_system_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_isp_system_l2_wtrans.attr.attr,
+	&rpi_axi_pmu_event_usb_system_l2_rtrans.attr.attr,
+	&rpi_axi_pmu_event_usb_system_l2_wtrans.attr.attr,
+	NULL,
+};
+
+static const struct attribute_group rpi_axi_pmu_events_group = {
+	.name = "events",
+	.attrs = rpi_axi_pmu_events_attrs,
+};
+
+/**
+ * cpumask_show() - Sysfs attribute callback to display assigned PMU CPU core
+ * @dev: Pointer to device structure
+ * @attr: Pointer to device attribute
+ * @buf: Output buffer for cpumask string representation
+ *
+ * Return: Number of bytes written to buffer.
+ */
+static ssize_t cpumask_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct rpi_axi_pmu *pmu = dev_get_drvdata(dev);
+
+	return cpumap_print_to_pagebuf(true, buf, cpumask_of(pmu->cpu));
+}
+static DEVICE_ATTR_RO(cpumask);
+
+static struct attribute *rpi_axi_pmu_cpumask_attrs[] = {
+	&dev_attr_cpumask.attr,
+	NULL,
+};
+
+static const struct attribute_group rpi_axi_pmu_cpumask_group = {
+	.attrs = rpi_axi_pmu_cpumask_attrs,
+};
+
+static const struct attribute_group *rpi_axi_pmu_attr_groups[] = {
+	&rpi_axi_pmu_format_group,
+	&rpi_axi_pmu_events_group,
+	&rpi_axi_pmu_cpumask_group,
+	NULL,
+};
+
+/**
+ * rpi_axi_pmu__validate_event() - Validates single event resource capability
+ * @pmu: Pointer to core PMU struct
+ * @fake_hw_events: Temporary array of watcher structures for pre-flight check
+ * @event: Pointer to perf_event being validated
+ *
+ * Return: true if event can be scheduled, false otherwise.
+ */
+static bool rpi_axi_pmu__validate_event(struct pmu *pmu,
+					struct rpi_axi_hw_events fake_hw_events[MON__MAX],
+					struct perf_event *event)
+{
+	enum monitor mon;
+
+	if (is_software_event(event))
+		return true;
+	if (event->pmu != pmu)
+		return false;
+
+	mon = config_to_monitor(event->attr.config);
+	return rpi_axi_hw_events__get_alloc_event_idx(&fake_hw_events[mon], event) >= 0;
+}
+
+/**
+ * rpi_axi_pmu__validate_group() - Validates event group scheduleability
+ * @event: Pointer to leader or sibling perf_event
+ *
+ * Simulates bus watcher allocation across both monitors to guarantee all events
+ * in the group can run simultaneously.
+ *
+ * Return: true if group is valid, false otherwise.
+ */
+static bool rpi_axi_pmu__validate_group(struct perf_event *event)
+{
+	struct perf_event *sibling, *leader = event->group_leader;
+	struct rpi_axi_hw_events fake_hw_events[MON__MAX];
+
+	rpi_axi_hw_events__init(&fake_hw_events[MON__SYSTEM]);
+	rpi_axi_hw_events__init(&fake_hw_events[MON__VPU]);
+
+	if (!rpi_axi_pmu__validate_event(event->pmu, fake_hw_events, leader))
+		return false;
+
+	for_each_sibling_event(sibling, leader) {
+		if (!rpi_axi_pmu__validate_event(event->pmu, fake_hw_events, sibling))
+			return false;
+	}
+	return rpi_axi_pmu__validate_event(event->pmu, fake_hw_events, event);
+}
+
+/**
+ * rpi_axi_pmu_event_init() - Perf callback to initialize a perf_event
+ * @event: Pointer to perf_event to initialize
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int rpi_axi_pmu_event_init(struct perf_event *event)
+{
+	struct rpi_axi_pmu *pmu;
+	struct device *dev;
+
+	if (event->attr.type != event->pmu->type)
+		return -ENOENT;
+
+	pmu = pmu_to_rpi_axi_pmu(event->pmu);
+	dev = pmu->pmu.dev;
+
+	if (!config_is_valid(pmu, event->attr.config)) {
+		dev_dbg(dev, "Invalid event config\n");
+		return -EINVAL;
+	}
+
+	if (is_sampling_event(event)) {
+		dev_dbg(dev, "Sampling not supported\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (event->cpu < 0) {
+		dev_dbg(dev, "Per-task data not supported\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (!rpi_axi_pmu__validate_group(event)) {
+		dev_dbg(dev, "Invalid event or grouping of events\n");
+		return -EINVAL;
+	}
+	event->hw.idx = -1;
+	return 0;
+}
+
+/**
+ * set_monitor_control() - Writes to global monitor control register
+ * @pmu: Pointer to PMU context
+ * @mon: Monitor selection (MON__SYSTEM or MON__VPU)
+ * @set: Control bitmask to write
+ */
+static void set_monitor_control(struct rpi_axi_pmu *pmu, enum monitor mon, u32 set)
+{
+	if (pmu->monitor[mon].use_mailbox_interface) {
+		u32 tmp[3] = {pmu->monitor[mon].mailbox + GEN_CTRL, 1, set};
+		int err;
+
+		might_sleep();
+		lockdep_assert_held(&pmu->vpu_mutex);
+		if (WARN_ON_ONCE(in_interrupt() || irqs_disabled()))
+			return;
+
+		err = rpi_firmware_property(pmu->firmware,
+					    RPI_FIRMWARE_SET_PERIPH_REG,
+					    tmp, sizeof(tmp));
+
+		if (err < 0 || tmp[1] != 1)
+			dev_err(&pmu->pdev->dev, "Failed to set monitor control\n");
+	} else {
+		lockdep_assert_held(&pmu->lock);
+		writel(set, pmu->monitor[mon].base_address + GEN_CTRL);
+	}
+}
+
+static int watcher_offset(const struct rpi_axi_pmu *pmu, enum monitor mon, int idx)
+{
+	return BW0_CTRL + idx * BW_PITCH;
+}
+
+/**
+ * set_bus_watcher_control() - Writes to a specific bus watcher control register
+ * @pmu: Pointer to PMU context
+ * @mon: Monitor selection
+ * @idx: Watcher index (0..2)
+ * @set: Control bitmask to write
+ */
+static void set_bus_watcher_control(struct rpi_axi_pmu *pmu, enum monitor mon, int idx, u32 set)
+{
+	int watcher = watcher_offset(pmu, mon, idx);
+
+	if (pmu->monitor[mon].use_mailbox_interface) {
+		u32 tmp[3] = {pmu->monitor[mon].mailbox + watcher, 1, set};
+		int err;
+
+		might_sleep();
+		lockdep_assert_held(&pmu->vpu_mutex);
+		if (WARN_ON_ONCE(in_interrupt() || irqs_disabled()))
+			return;
+
+		err = rpi_firmware_property(pmu->firmware,
+					    RPI_FIRMWARE_SET_PERIPH_REG,
+					    tmp, sizeof(tmp));
+		if (err < 0 || tmp[1] != 1)
+			dev_err(&pmu->pdev->dev, "Failed to set bus watcher control\n");
+	} else {
+		lockdep_assert_held(&pmu->lock);
+		writel(set, pmu->monitor[mon].base_address + watcher);
+	}
+}
+
+/**
+ * rpi_axi_pmu_enable_bus_watcher() - Enables a hardware bus watcher unit
+ * @pmu: Pointer to PMU context
+ * @mon: Monitor selection
+ * @idx: Watcher index (0..2)
+ */
+static void rpi_axi_pmu_enable_bus_watcher(struct rpi_axi_pmu *pmu, enum monitor mon, int idx)
+{
+	int bus, filter, bus_control;
+
+	if (pmu->monitor[mon].hw_events.enabled[idx])
+		return;
+
+	bus = pmu->monitor[mon].hw_events.monitored_bus[idx];
+	filter = pmu->monitor[mon].hw_events.filter[idx];
+
+	bus_control = BW_CTRL_ENABLE_BIT | (bus & 0x3F);
+	if (filter) {
+		bus_control |= BW_CTRL_ENABLE_ID_FILTER_BIT;
+		bus_control |= (filter & 0x1F) << BW_CTRL_BUS_FILTER_SHIFT;
+	}
+	set_bus_watcher_control(pmu, mon, idx, BW_CTRL_RESET_BIT);
+	set_bus_watcher_control(pmu, mon, idx, bus_control);
+
+	set_monitor_control(pmu, mon, GEN_CTL_RESET_BIT);
+	set_monitor_control(pmu, mon, GEN_CTL_ENABLE_BIT | GEN_CTL_WATCH_BIT);
+
+	pmu->monitor[mon].hw_events.enabled[idx] = true;
+}
+
+/**
+ * rpi_axi_pmu_disable_bus_watcher() - Resets and disables a hardware bus watcher unit
+ * @pmu: Pointer to PMU context
+ * @mon: Monitor selection
+ * @idx: Watcher index (0..2)
+ */
+static void rpi_axi_pmu_disable_bus_watcher(struct rpi_axi_pmu *pmu, enum monitor mon, int idx)
+{
+	if (!pmu->monitor[mon].hw_events.enabled[idx])
+		return;
+
+	set_bus_watcher_control(pmu, mon, idx, BW_CTRL_RESET_BIT);
+
+	pmu->monitor[mon].hw_events.enabled[idx] = false;
+}
+
+static int counter_offset(enum counter counter)
+{
+	switch (counter) {
+	case CNT__ATRANS: return BW_ATRANS_OFFSET;
+	case CNT__ATWAIT: return BW_ATWAIT_OFFSET;
+	case CNT__WTRANS: return BW_WTRANS_OFFSET;
+	case CNT__WTWAIT: return BW_WTWAIT_OFFSET;
+	case CNT__RTRANS: return BW_RTRANS_OFFSET;
+	case CNT__RTWAIT: return BW_RTWAIT_OFFSET;
+	default: return 0;
+	}
+}
+
+/**
+ * rpi_axi_pmu_read_counter() - Reads raw 32-bit hardware counter from watcher
+ * @pmu: Pointer to PMU context
+ * @mon: Monitor selection
+ * @idx: Watcher index (0..2)
+ * @counter: Metric counter type (enum counter, 0..8)
+ *
+ * Return: 32-bit raw hardware counter value.
+ */
+static u32 rpi_axi_pmu_read_counter(struct rpi_axi_pmu *pmu, enum monitor mon, int idx,
+				    enum counter counter)
+{
+	int watcher = watcher_offset(pmu, mon, idx);
+	int offset = counter_offset(counter);
+	u32 ret;
+
+	if (!pmu->monitor[mon].hw_events.enabled[idx])
+		return 0;
+
+	if (pmu->monitor[mon].use_mailbox_interface) {
+		u32 tmp[3] = {
+			pmu->monitor[mon].mailbox + watcher + offset,
+			1, -1
+		};
+		int err;
+
+		might_sleep();
+		lockdep_assert_held(&pmu->vpu_mutex);
+		if (WARN_ON_ONCE(in_interrupt() || irqs_disabled()))
+			return -1;
+
+		err = rpi_firmware_property(pmu->firmware,
+					    RPI_FIRMWARE_GET_PERIPH_REG,
+					    tmp, sizeof(tmp));
+
+		if (err < 0 || tmp[1] != 1)
+			dev_err(&pmu->pdev->dev, "Failed to read bus watcher\n");
+		ret = tmp[2];
+	} else {
+		lockdep_assert_held(&pmu->lock);
+		void __iomem *addr = pmu->monitor[mon].base_address + watcher + offset;
+		ret = readl(addr) & 0x7FFFFFFF;
+	}
+	return ret;
+}
+
+/**
+ * rpi_axi_pmu_read() - Perf callback to update event counter value
+ * @event: Pointer to perf_event being read
+ *
+ * Thread-safe counter update implementation:
+ * - System Monitor (MON__SYSTEM): Uses fast MMIO (~15ns), serialized via pmu->lock spinlock.
+ * - VPU Monitor (MON__VPU): Async background polling in process context (vpu_work).
+ *   Direct read() syscalls return cached count immediately without blocking.
+ */
+static void rpi_axi_pmu_read(struct perf_event *event)
+{
+	struct rpi_axi_pmu *pmu = pmu_to_rpi_axi_pmu(event->pmu);
+	enum monitor mon = config_to_monitor(event->attr.config);
+	enum counter counter = config_to_counter(event->attr.config);
+	u64 prev_count, new_count;
+	unsigned long flags;
+	u32 delta;
+
+	/* Mailbox VPU counters are polled asynchronously in background vpu_work.
+	 * MMIO monitors (System and BCM2712 VPU) are read synchronously.
+	 */
+	if (pmu->monitor[mon].use_mailbox_interface || event->hw.idx < 0)
+		return;
+
+	spin_lock_irqsave(&pmu->lock, flags);
+	if (!pmu->monitor[mon].hw_events.enabled[event->hw.idx]) {
+		spin_unlock_irqrestore(&pmu->lock, flags);
+		return;
+	}
+	prev_count = local64_read(&event->hw.prev_count);
+	new_count = rpi_axi_pmu_read_counter(pmu, mon, event->hw.idx, counter);
+	local64_set(&event->hw.prev_count, new_count);
+	delta = new_count - prev_count;
+	local64_add(delta, &event->count);
+	spin_unlock_irqrestore(&pmu->lock, flags);
+}
+
+/**
+ * rpi_axi_pmu_vpu_work_handler() - Background work handler for VPU monitor counter reads
+ * @work: Pointer to work_struct inside struct rpi_axi_pmu
+ *
+ * Runs in kernel process context where sleeping is allowed. Reads fresh VPU counter values over
+ * VideoCore Mailbox IPC under vpu_mutex and updates the cached perf event count safely.
+ * ABA pointer recycling races are prevented by validating per-slot sequence counters (event_gen).
+ * Multiplexing counter rotation baselines are established using the PERF_HES_UPTODATE flag.
+ */
+static void rpi_axi_pmu_vpu_work_handler(struct work_struct *work)
+{
+	struct rpi_axi_pmu *pmu = container_of(work, struct rpi_axi_pmu, vpu_work);
+
+	might_sleep();
+	mutex_lock(&pmu->vpu_mutex);
+	spin_lock_irq(&pmu->lock);
+
+	for (int i = 0; i < RPI_AXI_MAX_EVENTS; i++) {
+		struct perf_event *event = pmu->events[i];
+		enum counter counter;
+		u64 gen;
+		int idx;
+		u64 prev_count, new_count;
+		u32 delta;
+
+		if (!event || (event->hw.state & PERF_HES_STOPPED) ||
+		    config_to_monitor(event->attr.config) != MON__VPU)
+			continue;
+
+		gen = pmu->event_gen[i];
+		counter = config_to_counter(event->attr.config);
+		idx = event->hw.idx;
+
+		/* If VPU bus watcher is not enabled on hardware, enable it in process context */
+		if (!pmu->monitor[MON__VPU].hw_events.enabled[idx]) {
+			spin_unlock_irq(&pmu->lock);
+			rpi_axi_pmu_enable_bus_watcher(pmu, MON__VPU, idx);
+			spin_lock_irq(&pmu->lock);
+		}
+
+		/* Drop spinlock during Mailbox IPC read (which can sleep) */
+		spin_unlock_irq(&pmu->lock);
+
+		new_count = rpi_axi_pmu_read_counter(pmu, MON__VPU, idx, counter);
+
+		spin_lock_irq(&pmu->lock);
+
+		/*
+		 * Verify event pointer and generation sequence counter match
+		 * (ABA pointer recycling race prevention).
+		 */
+		if (pmu->events[i] == event &&
+		    pmu->event_gen[i] == gen &&
+		    !(event->hw.state & PERF_HES_STOPPED)) {
+			if (!(event->hw.state & PERF_HES_UPTODATE)) {
+				/* Initial baseline read for newly started/rotated VPU event */
+				local64_set(&event->hw.prev_count, new_count);
+				event->hw.state |= PERF_HES_UPTODATE;
+			} else {
+				prev_count = local64_read(&event->hw.prev_count);
+				local64_set(&event->hw.prev_count, new_count);
+				delta = new_count - prev_count;
+				local64_add(delta, &event->count);
+			}
+		}
+	}
+
+	spin_unlock_irq(&pmu->lock);
+	mutex_unlock(&pmu->vpu_mutex);
+}
+
+/**
+ * rpi_axi_pmu_timer_handler() - Periodic hrtimer callback for 32-bit counter overflow polling
+ * @timer: Pointer to hrtimer structure
+ *
+ * Runs in hard IRQ / atomic context.
+ * Holding pmu->lock, reads System monitor counters (MON__SYSTEM) via fast MMIO.
+ * Schedules background work (vpu_work) if active_vpu_events > 0.
+ *
+ * Return: HRTIMER_RESTART.
+ */
+static enum hrtimer_restart rpi_axi_pmu_timer_handler(struct hrtimer *timer)
+{
+	struct rpi_axi_pmu *pmu = container_of(timer, struct rpi_axi_pmu, hrtimer);
+	unsigned long flags;
+
+	spin_lock_irqsave(&pmu->lock, flags);
+	for (int i = 0; i < RPI_AXI_MAX_EVENTS; i++) {
+		struct perf_event *event = pmu->events[i];
+		enum counter counter;
+		u64 prev_count, new_count;
+		u32 delta;
+
+		if (!event || (event->hw.state & PERF_HES_STOPPED) ||
+		    config_to_monitor(event->attr.config) != MON__SYSTEM)
+			continue;
+
+		counter = config_to_counter(event->attr.config);
+		prev_count = local64_read(&event->hw.prev_count);
+		new_count = rpi_axi_pmu_read_counter(pmu, MON__SYSTEM,
+						    event->hw.idx, counter);
+		local64_set(&event->hw.prev_count, new_count);
+		delta = new_count - prev_count;
+		local64_add(delta, &event->count);
+	}
+
+	if (pmu->active_vpu_events > 0)
+		schedule_work(&pmu->vpu_work);
+	spin_unlock_irqrestore(&pmu->lock, flags);
+
+	hrtimer_forward_now(timer, RPI_AXI_PMU_TIMER_INTERVAL);
+	return HRTIMER_RESTART;
+}
+
+/**
+ * rpi_axi_pmu_start() - Starts monitoring on an allocated bus watcher
+ * @event: Pointer to perf_event being started
+ * @flags: Start control flags
+ */
+static void rpi_axi_pmu_start(struct perf_event *event, int flags)
+{
+	struct rpi_axi_pmu *pmu = pmu_to_rpi_axi_pmu(event->pmu);
+	enum monitor mon = config_to_monitor(event->attr.config);
+	enum counter counter = config_to_counter(event->attr.config);
+	unsigned long spinflags;
+
+	spin_lock_irqsave(&pmu->lock, spinflags);
+	event->hw.state = 0;
+	pmu->monitor[mon].hw_events.num_started++;
+	if (mon == MON__SYSTEM) {
+		rpi_axi_pmu_enable_bus_watcher(pmu, mon, event->hw.idx);
+		local64_set(&event->hw.prev_count,
+			    rpi_axi_pmu_read_counter(pmu, mon, event->hw.idx, counter));
+		event->hw.state |= PERF_HES_UPTODATE;
+	}
+	spin_unlock_irqrestore(&pmu->lock, spinflags);
+}
+
+/**
+ * rpi_axi_pmu_add() - Allocates a bus watcher resource and adds event to PMU
+ * @event: Pointer to perf_event being added
+ * @flags: Add control flags (e.g. PERF_EF_START)
+ *
+ * Return: 0 on success, -EAGAIN if no watcher slot is available.
+ */
+static int rpi_axi_pmu_add(struct perf_event *event, int flags)
+{
+	struct rpi_axi_pmu *pmu = pmu_to_rpi_axi_pmu(event->pmu);
+	enum monitor mon = config_to_monitor(event->attr.config);
+	struct rpi_axi_hw_events *hw_events = &pmu->monitor[mon].hw_events;
+	unsigned long spinflags;
+	int idx;
+
+	spin_lock_irqsave(&pmu->lock, spinflags);
+	idx = rpi_axi_hw_events__get_alloc_event_idx(hw_events, event);
+	if (idx < 0) {
+		spin_unlock_irqrestore(&pmu->lock, spinflags);
+		return -EAGAIN;
+	}
+
+	for (int i = 0; i < RPI_AXI_MAX_EVENTS; i++) {
+		if (!pmu->events[i]) {
+			pmu->events[i] = event;
+			pmu->event_gen[i]++;
+			break;
+		}
+	}
+
+	pmu->active_events++;
+	if (mon == MON__VPU)
+		pmu->active_vpu_events++;
+
+	if (pmu->active_events == 1)
+		hrtimer_start(&pmu->hrtimer, RPI_AXI_PMU_TIMER_INTERVAL, HRTIMER_MODE_REL_PINNED);
+
+	event->hw.idx = idx;
+	event->hw.state = PERF_HES_STOPPED;
+	spin_unlock_irqrestore(&pmu->lock, spinflags);
+
+	if (flags & PERF_EF_START)
+		rpi_axi_pmu_start(event, /*flags=*/0);
+	return 0;
+}
+
+/**
+ * rpi_axi_pmu_stop() - Stops counter monitoring for an event
+ * @event: Pointer to perf_event being stopped
+ * @flags: Stop control flags (e.g. PERF_EF_UPDATE)
+ */
+static void rpi_axi_pmu_stop(struct perf_event *event, int flags)
+{
+	struct rpi_axi_pmu *pmu = pmu_to_rpi_axi_pmu(event->pmu);
+	enum monitor mon = config_to_monitor(event->attr.config);
+	unsigned long spinflags;
+
+	if (event->hw.state & PERF_HES_STOPPED)
+		return;
+
+	if (flags & PERF_EF_UPDATE) {
+		rpi_axi_pmu_read(event);
+		event->hw.state |= PERF_HES_UPTODATE;
+	}
+
+	spin_lock_irqsave(&pmu->lock, spinflags);
+	event->hw.state |= PERF_HES_STOPPED;
+	pmu->monitor[mon].hw_events.num_started--;
+	spin_unlock_irqrestore(&pmu->lock, spinflags);
+}
+
+/**
+ * rpi_axi_pmu_del() - Deallocates watcher resource and removes event from PMU
+ * @event: Pointer to perf_event being removed
+ * @flags: Delete control flags
+ */
+static void rpi_axi_pmu_del(struct perf_event *event, int flags)
+{
+	struct rpi_axi_pmu *pmu = pmu_to_rpi_axi_pmu(event->pmu);
+	enum monitor mon = config_to_monitor(event->attr.config);
+	unsigned long spinflags;
+	int idx = event->hw.idx;
+
+	if (idx < 0)
+		return;
+
+	rpi_axi_pmu_stop(event, PERF_EF_UPDATE);
+
+	spin_lock_irqsave(&pmu->lock, spinflags);
+	for (int i = 0; i < RPI_AXI_MAX_EVENTS; i++) {
+		if (pmu->events[i] == event) {
+			pmu->events[i] = NULL;
+			pmu->event_gen[i]++;
+			break;
+		}
+	}
+
+	if (pmu->monitor[mon].hw_events.monitored_bus[idx] >= 0) {
+		pmu->monitor[mon].hw_events.refcount[idx]--;
+		if (pmu->monitor[mon].hw_events.refcount[idx] == 0) {
+			if (mon == MON__SYSTEM)
+				rpi_axi_pmu_disable_bus_watcher(pmu, mon, idx);
+			pmu->monitor[mon].hw_events.monitored_bus[idx] = -1;
+			pmu->monitor[mon].hw_events.filter[idx] = BCM2835_FLT__NONE;
+			pmu->monitor[mon].hw_events.num_monitored--;
+			if (mon == MON__SYSTEM && pmu->monitor[mon].hw_events.num_monitored == 0)
+				set_monitor_control(pmu, mon, GEN_CTL_RESET_BIT);
+		}
+	}
+
+	event->hw.idx = -1;
+	pmu->active_events--;
+	if (mon == MON__VPU)
+		pmu->active_vpu_events--;
+
+	if (pmu->active_events == 0) {
+		spin_unlock_irqrestore(&pmu->lock, spinflags);
+		hrtimer_cancel(&pmu->hrtimer);
+		return;
+	}
+	spin_unlock_irqrestore(&pmu->lock, spinflags);
+}
+
+/**
+ * rpi_axi_pmu_offline_cpu() - CPU hotplug notifier callback when designated CPU goes offline
+ * @cpu: CPU core number being taken offline
+ * @node: Pointer to hlist_node inside struct rpi_axi_pmu
+ *
+ * Return: 0.
+ */
+static int rpi_axi_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
+{
+	struct rpi_axi_pmu *pmu = hlist_entry_safe(node, struct rpi_axi_pmu, cpuhp_node);
+	unsigned int target;
+
+	if (cpu != pmu->cpu)
+		return 0;
+
+	target = cpumask_any_but(cpu_online_mask, cpu);
+	if (target >= nr_cpu_ids)
+		return 0;
+
+	perf_pmu_migrate_context(&pmu->pmu, cpu, target);
+	pmu->cpu = target;
+	return 0;
+}
+
+/**
+ * rpi_axi_pmu__init() - Internal PMU driver initialization called during probe
+ * @pmu: Pointer to PMU context
+ * @pdev: Platform device pointer
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int rpi_axi_pmu__init(struct rpi_axi_pmu *pmu, struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *fw_node;
+	int ret;
+
+	spin_lock_init(&pmu->lock);
+	mutex_init(&pmu->vpu_mutex);
+
+	pmu->chip = CHIP_BCM2835;
+
+	pmu->pmu = (struct pmu) {
+		.module = THIS_MODULE,
+		.attr_groups	= rpi_axi_pmu_attr_groups,
+		.task_ctx_nr    = perf_invalid_context,
+		.event_init     = rpi_axi_pmu_event_init,
+		.add            = rpi_axi_pmu_add,
+		.del            = rpi_axi_pmu_del,
+		.start          = rpi_axi_pmu_start,
+		.stop           = rpi_axi_pmu_stop,
+		.read           = rpi_axi_pmu_read,
+		.capabilities   = PERF_PMU_CAP_NO_EXCLUDE,
+	};
+	pmu->pdev = pdev;
+	pmu->cpu = raw_smp_processor_id();
+	hrtimer_setup(&pmu->hrtimer, rpi_axi_pmu_timer_handler, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	INIT_WORK(&pmu->vpu_work, rpi_axi_pmu_vpu_work_handler);
+
+	if (pmu->chip == CHIP_BCM2835) {
+		pmu->monitor[MON__SYSTEM].use_mailbox_interface = false;
+		pmu->monitor[MON__VPU].use_mailbox_interface = true;
+		fw_node = of_parse_phandle(dev->of_node, "firmware", 0);
+		if (fw_node) {
+			pmu->firmware = rpi_firmware_get(fw_node);
+			of_node_put(fw_node);
+			if (!pmu->firmware)
+				return -EPROBE_DEFER;
+		}
+	} else {
+		pmu->monitor[MON__SYSTEM].use_mailbox_interface = false;
+		pmu->monitor[MON__VPU].use_mailbox_interface = false;
+	}
+
+	for (int i = 0; i < MON__MAX; i++) {
+		rpi_axi_hw_events__init(&pmu->monitor[i].hw_events);
+
+		if (pmu->monitor[i].use_mailbox_interface) {
+			ret = of_property_read_u32_index(dev->of_node, "reg", i * 2,
+							 &pmu->monitor[i].mailbox);
+			if (ret) {
+				dev_err(dev, "Error reading mailbox reg %d %d\n", i * 2, ret);
+				goto err_firmware_put;
+			}
+		} else {
+			struct resource *resource = platform_get_resource(pdev, IORESOURCE_MEM, i);
+
+			if (!resource)
+				continue;
+
+			pmu->monitor[i].base_address = devm_ioremap_resource(dev, resource);
+			if (IS_ERR(pmu->monitor[i].base_address)) {
+				ret = PTR_ERR(pmu->monitor[i].base_address);
+				dev_err(dev, "Error devm_ioremap_resource failed %d\n", ret);
+				goto err_firmware_put;
+			}
+		}
+	}
+
+	ret = cpuhp_state_add_instance(rpi_axi_pmu_cpuhp_state, &pmu->cpuhp_node);
+	if (ret) {
+		dev_err(dev, "Failed to add cpuhp instance %d\n", ret);
+		goto err_firmware_put;
+	}
+
+	ret = perf_pmu_register(&pmu->pmu, PMU_NAME, /*type=*/-1);
+	if (ret) {
+		dev_err(dev, "PMU register failed %d\n", ret);
+		goto err_cpuhp;
+	}
+	return 0;
+
+err_cpuhp:
+	cpuhp_state_remove_instance(rpi_axi_pmu_cpuhp_state, &pmu->cpuhp_node);
+err_firmware_put:
+	if (pmu->firmware)
+		rpi_firmware_put(pmu->firmware);
+	return ret;
+}
+
+/**
+ * rpi_axi_pmu__exit() - Internal PMU teardown called during remove
+ * @pmu: Pointer to PMU context
+ */
+static void rpi_axi_pmu__exit(struct rpi_axi_pmu *pmu)
+{
+	cpuhp_state_remove_instance(rpi_axi_pmu_cpuhp_state, &pmu->cpuhp_node);
+	cancel_work_sync(&pmu->vpu_work);
+	if (pmu->firmware)
+		rpi_firmware_put(pmu->firmware);
+	perf_pmu_unregister(&pmu->pmu);
+}
+
+/* --- DRIVER ENTRY POINTS ----------------------------------------- */
+
+/**
+ * rpi_axi_pmu_probe() - Platform driver probe entry point
+ * @pdev: Pointer to platform_device
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int rpi_axi_pmu_probe(struct platform_device *pdev)
+{
+	struct rpi_axi_pmu *pmu;
+
+	pmu = devm_kzalloc(&pdev->dev, sizeof(*pmu), GFP_KERNEL);
+	if (!pmu)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, pmu);
+	return rpi_axi_pmu__init(pmu, pdev);
+}
+
+/**
+ * rpi_axi_pmu_remove() - Platform driver remove entry point
+ * @pdev: Pointer to platform_device
+ */
+static void rpi_axi_pmu_remove(struct platform_device *pdev)
+{
+	struct rpi_axi_pmu *pmu;
+
+	pmu = platform_get_drvdata(pdev);
+	rpi_axi_pmu__exit(pmu);
+}
+
+/* Devices matching this driver in Device Tree */
+static const struct of_device_id rpi_axi_pmu_match[] = {
+	{
+		.compatible = "brcm,bcm2835-axiperf",
+		.data = (void *)CHIP_BCM2835,
+	},
+	{
+		.compatible = "brcm,bcm2711-axiperf",
+		.data = (void *)CHIP_BCM2835,
+	},
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, rpi_axi_pmu_match);
+
+static struct platform_driver rpi_axi_pmu_driver  = {
+	.probe =	rpi_axi_pmu_probe,
+	.remove =	rpi_axi_pmu_remove,
+	.driver = {
+		.name   = PMU_NAME,
+		.of_match_table = of_match_ptr(rpi_axi_pmu_match),
+	},
+};
+
+/**
+ * rpi_axi_pmu_driver_init() - Module initialization entry point
+ *
+ * Registers the dynamic CPU hotplug state and the platform driver.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int __init rpi_axi_pmu_driver_init(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "perf/rpi_axi_pmu:online",
+				      NULL, rpi_axi_pmu_offline_cpu);
+	if (ret < 0)
+		return ret;
+
+	rpi_axi_pmu_cpuhp_state = ret;
+
+	ret = platform_driver_register(&rpi_axi_pmu_driver);
+	if (ret)
+		cpuhp_remove_multi_state(rpi_axi_pmu_cpuhp_state);
+
+	return ret;
+}
+module_init(rpi_axi_pmu_driver_init);
+
+/**
+ * rpi_axi_pmu_driver_exit() - Module cleanup entry point
+ *
+ * Unregisters the platform driver and CPU hotplug state.
+ */
+static void __exit rpi_axi_pmu_driver_exit(void)
+{
+	platform_driver_unregister(&rpi_axi_pmu_driver);
+	cpuhp_remove_multi_state(rpi_axi_pmu_cpuhp_state);
+}
+module_exit(rpi_axi_pmu_driver_exit);
+
+MODULE_LICENSE("GPL");
-- 
2.55.0.679.g6767b8d81c-goog