Message-ID: <ea3fda8c-2b7d-4902-9bda-d97d7b090cff@arm.com>
Date: Fri, 15 Aug 2025 13:39:27 +0100
From: Robin Murphy <robin.murphy@....com>
To: Koichi Okuno <fj2767dz@...itsu.com>, Will Deacon <will@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Jonathan Corbet <corbet@....net>,
 Catalin Marinas <catalin.marinas@....com>,
 Gowthami Thiagarajan <gthiagarajan@...vell.com>,
 Linu Cherian <lcherian@...vell.com>, linux-arm-kernel@...ts.infradead.org,
 Bjorn Andersson <quic_bjorande@...cinc.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Neil Armstrong <neil.armstrong@...aro.org>, Arnd Bergmann <arnd@...db.de>,
 Nícolas F. R. A. Prado <nfraprado@...labora.com>,
 Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/2] perf: Fujitsu: Add the Uncore MAC PMU driver

On 2025-08-15 4:47 am, Koichi Okuno wrote:
> This adds a new dynamic PMU to the Perf Events framework to program and
> control the Uncore MAC PMUs in Fujitsu chips.
> 
> This driver was created with reference to drivers/perf/qcom_l3_pmu.c.
> 
> This driver exports formatting and event information to sysfs so it can
> be used by the perf user space tools with the syntaxes:
> 
> perf stat -e mac_iod0_mac0_ch0/ea-mac/ ls
> perf stat -e mac_iod0_mac0_ch0/event=0x80/ ls
> 
> FUJITSU-MONAKA PMU Events Specification v1.1 URL:
> https://github.com/fujitsu/FUJITSU-MONAKA
> 
> Signed-off-by: Koichi Okuno <fj2767dz@...itsu.com>
> ---
>   .../admin-guide/perf/fujitsu_mac_pmu.rst      |  73 +++
>   Documentation/admin-guide/perf/index.rst      |   1 +
>   drivers/perf/Kconfig                          |   9 +
>   drivers/perf/Makefile                         |   1 +
>   drivers/perf/fujitsu_mac_pmu.c                | 552 ++++++++++++++++++
>   5 files changed, 636 insertions(+)
>   create mode 100644 Documentation/admin-guide/perf/fujitsu_mac_pmu.rst
>   create mode 100644 drivers/perf/fujitsu_mac_pmu.c
> 
> diff --git a/Documentation/admin-guide/perf/fujitsu_mac_pmu.rst b/Documentation/admin-guide/perf/fujitsu_mac_pmu.rst
> new file mode 100644
> index 000000000000..383f3c1bbde7
> --- /dev/null
> +++ b/Documentation/admin-guide/perf/fujitsu_mac_pmu.rst
> @@ -0,0 +1,73 @@
> +====================================================
> +Fujitsu Uncore MAC Performance Monitoring Unit (PMU)
> +====================================================
> +
> +This driver supports the Uncore MAC PMUs found in Fujitsu chips.
> +Each MAC PMU on these chips is exposed as a uncore perf PMU with device name
> +mac_iod<iod>_mac<mac>_ch<ch>.
> +
> +The driver provides a description of its available events and configuration
> +options in sysfs, see /sys/bus/event_sources/devices/mac_iod<iod>_mac<mac>_ch<ch>/.
> +This driver exports:
> +- formats, used by perf user space and other tools to configure events
> +- events, used by perf user space and other tools to create events
> +  symbolically, e.g.:
> +    perf stat -a -e mac_iod0_mac0_ch0/event=0x21/ ls
> +- cpumask, used by perf user space and other tools to know on which CPUs
> +  to open the events
> +
> +This driver supports the following events:
> +- cycles
> +  This event counts MAC cycles at MAC frequency.
> +- read-count
> +  This event counts the number of read requests to MAC.
> +- read-count-request
> +  This event counts the number of read requests including retry to MAC.
> +- read-count-return
> +  This event counts the number of responses to read requests to MAC.
> +- read-count-request-pftgt
> +  This event counts the number of read requests including retry with PFTGT
> +  flag.
> +- read-count-request-normal
> +  This event counts the number of read requests including retry without PFTGT
> +  flag.
> +- read-count-return-pftgt-hit
> +  This event counts the number of responses to read requests which hit the
> +  PFTGT buffer.
> +- read-count-return-pftgt-miss
> +  This event counts the number of responses to read requests which miss the
> +  PFTGT buffer.
> +- read-wait
> +  This event counts outstanding read requests issued by DDR memory controller
> +  per cycle.
> +- write-count
> +  This event counts the number of write requests to MAC (including zero write,
> +  full write, partial write, write cancel).
> +- write-count-write
> +  This event counts the number of full write requests to MAC (not including
> +  zero write).
> +- write-count-pwrite
> +  This event counts the number of partial write requests to MAC.
> +- memory-read-count
> +  This event counts the number of read requests from MAC to memory.
> +- memory-write-count
> +  This event counts the number of full write requests from MAC to memory.
> +- memory-pwrite-count
> +  This event counts the number of partial write requests from MAC to memory.
> +- ea-mac
> +  This event counts energy consumption of MAC.
> +- ea-memory
> +  This event counts energy consumption of memory.
> +- ea-memory-mac-write
> +  This event counts the number of write requests from MAC to memory.
> +- ea-ha
> +  This event counts energy consumption of HA.
> +
> +  'ea' is the abbreviation for 'Energy Analyzer'.
> +
> +Examples for use with perf::
> +
> +  perf stat -e mac_iod0_mac0_ch0/ea-mac/ ls
> +
> +Given that these are uncore PMUs the driver does not support sampling, therefore
> +"perf record" will not work. Per-task perf sessions are not supported.
> diff --git a/Documentation/admin-guide/perf/index.rst b/Documentation/admin-guide/perf/index.rst
> index 072b510385c4..e0262060db17 100644
> --- a/Documentation/admin-guide/perf/index.rst
> +++ b/Documentation/admin-guide/perf/index.rst
> @@ -29,3 +29,4 @@ Performance monitor support
>      cxl
>      ampere_cspmu
>      mrvl-pem-pmu
> +   fujitsu_mac_pmu
> diff --git a/drivers/perf/Kconfig b/drivers/perf/Kconfig
> index a9188dec36fe..ab4e44c99a53 100644
> --- a/drivers/perf/Kconfig
> +++ b/drivers/perf/Kconfig
> @@ -178,6 +178,15 @@ config FSL_IMX9_DDR_PMU
>   	 can give information about memory throughput and other related
>   	 events.
>   
> +config FUJITSU_MAC_PMU
> +	bool "Fujitsu Uncore MAC PMU"

Why not a module? Note that copying some other driver that itself has no 
good reason not to be modular really doesn't count. TBH I'm not sure why 
you've focused on qcom_l3 in the first place - AFAICS this has nothing 
in common with that beyond what is common to teh majority of other 
MMIO-based system PMU drivers as well.

(And frankly I find modules so much more convenient just for development 
and debugging, regardless of distro/end user concerns!)

> +	depends on (ARM64 && (ACPI || COMPILE_TEST))

Not "(ARM64 && ACPI) || COMPILE_TEST"? I don't see any obvious 
compile-time dependency on a particular CPU architecture.

(you can #include <linux/io-64-nonatomic-lo-hi.h> to get 
readq()/writeq() fallbacks for 32-bit build-tests)
> +	help
> +	 Provides support for the Uncore MAC performance monitor unit (PMU)
> +	 in Fujitsu processors.
> +	 Adds the Uncore MAC PMU into the perf events subsystem for
> +	 monitoring Uncore MAC events.
> +
>   config QCOM_L2_PMU
>   	bool "Qualcomm Technologies L2-cache PMU"
>   	depends on ARCH_QCOM && ARM64 && ACPI
> diff --git a/drivers/perf/Makefile b/drivers/perf/Makefile
> index 192fc8b16204..be7f74c3b14c 100644
> --- a/drivers/perf/Makefile
> +++ b/drivers/perf/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_ARM_SMMU_V3_PMU) += arm_smmuv3_pmu.o
>   obj-$(CONFIG_FSL_IMX8_DDR_PMU) += fsl_imx8_ddr_perf.o
>   obj-$(CONFIG_FSL_IMX9_DDR_PMU) += fsl_imx9_ddr_perf.o
>   obj-$(CONFIG_HISI_PMU) += hisilicon/
> +obj-$(CONFIG_FUJITSU_MAC_PMU) += fujitsu_mac_pmu.o
>   obj-$(CONFIG_QCOM_L2_PMU)	+= qcom_l2_pmu.o
>   obj-$(CONFIG_QCOM_L3_PMU) += qcom_l3_pmu.o
>   obj-$(CONFIG_RISCV_PMU) += riscv_pmu.o
> diff --git a/drivers/perf/fujitsu_mac_pmu.c b/drivers/perf/fujitsu_mac_pmu.c
> new file mode 100644
> index 000000000000..1031e0221bb2
> --- /dev/null
> +++ b/drivers/perf/fujitsu_mac_pmu.c
> @@ -0,0 +1,552 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Driver for the Uncore MAC PMUs in Fujitsu chips.
> + *
> + * See Documentation/admin-guide/perf/fujitsu_mac_pmu.rst for more details.
> + *
> + * This driver is based on drivers/perf/qcom_l3_pmu.c
> + * Copyright (c) 2015-2017, The Linux Foundation. All rights reserved.
> + * Copyright (c) 2024 Fujitsu. All rights reserved.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/bitops.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/list.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/perf_event.h>
> +#include <linux/platform_device.h>
> +
> +/* Number of counters on each PMU */
> +#define MAC_NUM_COUNTERS  8
> +/* Mask for the event type field within perf_event_attr.config and EVTYPE reg */
> +#define MAC_EVTYPE_MASK   0xFF
> +
> +/* Perfmon registers */
> +#define MAC_PM_EVCNTR(__cntr)           (0x000 + (__cntr) * 8)
> +#define MAC_PM_CNTCTL(__cntr)           (0x100 + (__cntr) * 8)
> +#define MAC_PM_CNTCTL_RESET             0
> +#define MAC_PM_EVTYPE(__cntr)           (0x200 + (__cntr) * 8)
> +#define MAC_PM_EVTYPE_EVSEL(__val)      FIELD_GET(MAC_EVTYPE_MASK, __val)
> +#define MAC_PM_CR                       0x400
> +#define MAC_PM_CR_RESET                 BIT(1)
> +#define MAC_PM_CR_ENABLE                BIT(0)
> +#define MAC_PM_CNTENSET                 0x410
> +#define MAC_PM_CNTENSET_IDX(__cntr)     BIT(__cntr)
> +#define MAC_PM_CNTENCLR                 0x418
> +#define MAC_PM_CNTENCLR_IDX(__cntr)     BIT(__cntr)
> +#define MAC_PM_CNTENCLR_RESET           0xFF
> +#define MAC_PM_INTENSET                 0x420
> +#define MAC_PM_INTENSET_IDX(__cntr)     BIT(__cntr)
> +#define MAC_PM_INTENCLR                 0x428
> +#define MAC_PM_INTENCLR_IDX(__cntr)     BIT(__cntr)
> +#define MAC_PM_INTENCLR_RESET           0xFF
> +#define MAC_PM_OVSR                     0x440
> +#define MAC_PM_OVSR_OVSRCLR_RESET       0xFF
> +
> +#define MAC_EVENT_CYCLES                        0x000
> +#define MAC_EVENT_READ_COUNT                    0x010
> +#define MAC_EVENT_READ_COUNT_REQUEST            0x011
> +#define MAC_EVENT_READ_COUNT_RETURN             0x012
> +#define MAC_EVENT_READ_COUNT_REQUEST_PFTGT      0x013
> +#define MAC_EVENT_READ_COUNT_REQUEST_NORMAL     0x014
> +#define MAC_EVENT_READ_COUNT_RETURN_PFTGT_HIT   0x015
> +#define MAC_EVENT_READ_COUNT_RETURN_PFTGT_MISS  0x016
> +#define MAC_EVENT_READ_WAIT                     0x017
> +#define MAC_EVENT_WRITE_COUNT                   0x020
> +#define MAC_EVENT_WRITE_COUNT_WRITE             0x021
> +#define MAC_EVENT_WRITE_COUNT_PWRITE            0x022
> +#define MAC_EVENT_MEMORY_READ_COUNT             0x040
> +#define MAC_EVENT_MEMORY_WRITE_COUNT            0x050
> +#define MAC_EVENT_MEMORY_PWRITE_COUNT           0x060
> +#define MAC_EVENT_EA_MAC                        0x080
> +#define MAC_EVENT_EA_MEMORY                     0x090
> +#define MAC_EVENT_EA_MEMORY_MAC_WRITE           0x092
> +#define MAC_EVENT_EA_HA                         0x0a0

If these are strictly 8-bit values (per MAC_EVTYPE_MASK) then please 
drop the confusingly-significant-looking leading 0s.

> +
> +struct mac_pmu {
> +	struct pmu		pmu;
> +	struct hlist_node	node;
> +	void __iomem		*regs;
> +	struct perf_event	*events[MAC_NUM_COUNTERS];
> +	unsigned long		used_mask[BITS_TO_LONGS(MAC_NUM_COUNTERS)];
> +	cpumask_t		cpumask;
FWIW if you only associate with a single CPU then you can just store an 
int rather than a whole cpumask (plenty of examples in other drivers)

> +};
> +
> +#define to_mac_pmu(p) (container_of(p, struct mac_pmu, pmu))
> +
> +static int mac_pmu_cpuhp_state;
> +
> +static void fujitsu_mac_counter_start(struct perf_event *event)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(event->pmu);
> +	int idx = event->hw.idx;
> +
> +	/* Initialize the hardware counter and reset prev_count*/
> +	local64_set(&event->hw.prev_count, 0);
> +	writeq_relaxed(0, macpmu->regs + MAC_PM_EVCNTR(idx));
> +
> +	/* Set the event type */
> +	writeq_relaxed(MAC_PM_EVTYPE_EVSEL(event->attr.config), macpmu->regs + MAC_PM_EVTYPE(idx));
> +
> +	/* Enable interrupt generation by this counter */
> +	writeq_relaxed(MAC_PM_INTENSET_IDX(idx), macpmu->regs + MAC_PM_INTENSET);
> +
> +	/* Finally, enable the counter */
> +	writeq_relaxed(MAC_PM_CNTCTL_RESET, macpmu->regs + MAC_PM_CNTCTL(idx));
> +	writeq_relaxed(MAC_PM_CNTENSET_IDX(idx), macpmu->regs + MAC_PM_CNTENSET);
> +}
> +
> +static void fujitsu_mac_counter_stop(struct perf_event *event,
> +				     int flags)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(event->pmu);
> +	int idx = event->hw.idx;
> +
> +	/* Disable the counter */
> +	writeq_relaxed(MAC_PM_CNTENCLR_IDX(idx), macpmu->regs + MAC_PM_CNTENCLR);
> +
> +	/* Disable interrupt generation by this counter */
> +	writeq_relaxed(MAC_PM_INTENCLR_IDX(idx), macpmu->regs + MAC_PM_INTENCLR);
> +}
> +
> +static void fujitsu_mac_counter_update(struct perf_event *event)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(event->pmu);
> +	int idx = event->hw.idx;
> +	u64 prev, new;
> +
> +	do {
> +		prev = local64_read(&event->hw.prev_count);
> +		new = readq_relaxed(macpmu->regs + MAC_PM_EVCNTR(idx));
> +	} while (local64_cmpxchg(&event->hw.prev_count, prev, new) != prev);
> +
> +	local64_add(new - prev, &event->count);
> +}
> +
> +static inline void fujitsu_mac__init(struct mac_pmu *macpmu)
> +{
> +	int i;
> +
> +	writeq_relaxed(MAC_PM_CR_RESET, macpmu->regs + MAC_PM_CR);
> +
> +	writeq_relaxed(MAC_PM_CNTENCLR_RESET, macpmu->regs + MAC_PM_CNTENCLR);
> +	writeq_relaxed(MAC_PM_INTENCLR_RESET, macpmu->regs + MAC_PM_INTENCLR);
> +	writeq_relaxed(MAC_PM_OVSR_OVSRCLR_RESET, macpmu->regs + MAC_PM_OVSR);
> +
> +	for (i = 0; i < MAC_NUM_COUNTERS; ++i) {
> +		writeq_relaxed(MAC_PM_CNTCTL_RESET, macpmu->regs + MAC_PM_CNTCTL(i));
> +		writeq_relaxed(MAC_PM_EVTYPE_EVSEL(0), macpmu->regs + MAC_PM_EVTYPE(i));
> +	}
> +
> +	/*
> +	 * Use writeq here to ensure all programming commands are done
> +	 * before proceeding
> +	 */

Are you certain an explicit barrier is necessary here? Since your 
Kconfig implies this should only ever run on ARM64, the ioremap() 
results in a Device-nGnRx memory type, for which the CPU architecture 
already requires that accesses to the same peripheral occur in program 
order.

> +	writeq(MAC_PM_CR_ENABLE, macpmu->regs + MAC_PM_CR);
> +}
> +
> +static irqreturn_t fujitsu_mac__handle_irq(int irq_num, void *data)
> +{
> +	struct mac_pmu *macpmu = data;
> +	/* Read the overflow status register */
> +	long status = readq_relaxed(macpmu->regs + MAC_PM_OVSR);
> +	int idx;
> +
> +	if (status == 0)
> +		return IRQ_NONE;
> +
> +	/* Clear the bits we read on the overflow status register */
> +	writeq_relaxed(status, macpmu->regs + MAC_PM_OVSR);
> +
> +	for_each_set_bit(idx, &status, MAC_NUM_COUNTERS) {
> +		struct perf_event *event;
> +
> +		event = macpmu->events[idx];
> +		if (!event)
> +			continue;
> +
> +		fujitsu_mac_counter_update(event);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void fujitsu_mac__pmu_enable(struct pmu *pmu)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(pmu);
> +
> +	/* Ensure the other programming commands are observed before enabling */
> +	wmb();

Same here. At best it might be somewhat logical to have a DSB *after* 
the enable, as below, to try to ensure the PMU itself has seen the write 
if it was early-acknowledged, but most drivers don't bother since we're 
hardly dealing with cycle-accurate timings here anyway.

> +	writeq_relaxed(MAC_PM_CR_ENABLE, macpmu->regs + MAC_PM_CR);
> +}
> +
> +static void fujitsu_mac__pmu_disable(struct pmu *pmu)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(pmu);
> +
> +	writeq_relaxed(0, macpmu->regs + MAC_PM_CR);
> +
> +	/* Ensure the basic counter unit is stopped before proceeding */
> +	wmb();
> +}
> +
> +/*
> + * We must NOT create groups containing events from multiple hardware PMUs,
> + * although mixing different software and hardware PMUs is allowed.
> + */

Let's stop copying that comment around, it really isn't relevant any longer.

> +static bool fujitsu_mac__validate_event_group(struct perf_event *event)
> +{
> +	struct perf_event *leader = event->group_leader;
> +	struct perf_event *sibling;
> +	int counters;
> +
> +	if (leader->pmu != event->pmu && !is_software_event(leader))
> +		return false;
> +
> +	/* The sum of the counters used by the event and its leader event */
> +	counters = 2;

This is mis-counting a software leader as this PMU's event, but also 
mishandling the case when leader == event and it's not valid to touch 
the sibling list. What you want here is to simply count your own events:

	int counters = 1;

	if (leader == event)
		return true;

	if (leader->pmu == event->pmu)
		counters++;

> +
> +	for_each_sibling_event(sibling, leader) {
> +		if (is_software_event(sibling))
> +			continue;
> +		if (sibling->pmu != event->pmu)
> +			return false;
> +		counters++;

And here just:

		if (sibling->pmu == event->pmu)
			counters++;

The core code will take care of rejecting inappropriate cross-PMU groups.

> +	}
> +
> +	/*
> +	 * If the group requires more counters than the HW has, it
> +	 * cannot ever be scheduled.
> +	 */
> +	return counters <= MAC_NUM_COUNTERS;
> +}
> +
> +static int fujitsu_mac__event_init(struct perf_event *event)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(event->pmu);
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	/* Is the event for this PMU? */
> +	if (event->attr.type != event->pmu->type)
> +		return -ENOENT;
> +
> +	/*
> +	 * Sampling not supported since these events are not
> +	 * core-attributable.
> +	 */
> +	if (hwc->sample_period)
> +		return -EINVAL;

Strictly that's redundant now that you added PERF_PMU_CAP_NO_INTERRUPT, 
however I'm now trying to remove NO_INTERRUPT, so perhaps it might be 
better to keep this for the moment depending on how things end up landing.
  > +
> +	/*
> +	 * Task mode not available, we run the counters as socket counters,
> +	 * not attributable to any CPU and therefore cannot attribute per-task.
> +	 */
> +	if (event->cpu < 0)
> +		return -EINVAL;

You can drop this, perf_event_alloc() already takes care of it (see the 
CPU/task check on entry and the "Disallow uncore-task events" comment 
later - there's no harm if the driver itself nominally accepts the event 
in between)

> +
> +	/* Validate the group */
> +	if (!fujitsu_mac__validate_event_group(event))
> +		return -EINVAL;
> +
> +	hwc->idx = -1;
> +
> +	/*
> +	 * Many perf core operations (eg. events rotation) operate on a
> +	 * single CPU context. This is obvious for CPU PMUs, where one
> +	 * expects the same sets of events being observed on all CPUs,
> +	 * but can lead to issues for off-core PMUs, like this one, where
> +	 * each event could be theoretically assigned to a different CPU.
> +	 * To mitigate this, we enforce CPU assignment to one designated
> +	 * processor (the one described in the "cpumask" attribute exported
> +	 * by the PMU device). perf user space tools honor this and avoid
> +	 * opening more than one copy of the events.
> +	 */
> +	event->cpu = cpumask_first(&macpmu->cpumask);
> +
> +	return 0;
> +}
> +
> +static void fujitsu_mac__event_start(struct perf_event *event, int flags)
> +{
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	hwc->state = 0;
> +	fujitsu_mac_counter_start(event);
> +}
> +
> +static void fujitsu_mac__event_stop(struct perf_event *event, int flags)
> +{
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	if (hwc->state & PERF_HES_STOPPED)
> +		return;
> +
> +	fujitsu_mac_counter_stop(event, flags);
> +	if (flags & PERF_EF_UPDATE)
> +		fujitsu_mac_counter_update(event);
> +	hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
> +}
> +
> +static int fujitsu_mac__event_add(struct perf_event *event, int flags)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(event->pmu);
> +	struct hw_perf_event *hwc = &event->hw;
> +	int idx;
> +
> +	/* Try to allocate a counter. */
> +	idx = bitmap_find_free_region(macpmu->used_mask, MAC_NUM_COUNTERS, 0);
> +	if (idx < 0)
> +		/* The counters are all in use. */
> +		return -EAGAIN;
> +
> +	hwc->idx = idx;
> +	hwc->state = PERF_HES_STOPPED | PERF_HES_UPTODATE;
> +	macpmu->events[idx] = event;
> +
> +	if (flags & PERF_EF_START)
> +		fujitsu_mac__event_start(event, 0);
> +
> +	/* Propagate changes to the userspace mapping. */
> +	perf_event_update_userpage(event);
> +
> +	return 0;
> +}
> +
> +static void fujitsu_mac__event_del(struct perf_event *event, int flags)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(event->pmu);
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	/* Stop and clean up */
> +	fujitsu_mac__event_stop(event, flags | PERF_EF_UPDATE);
> +	macpmu->events[hwc->idx] = NULL;
> +	bitmap_release_region(macpmu->used_mask, hwc->idx, 0);
> +
> +	/* Propagate changes to the userspace mapping. */
> +	perf_event_update_userpage(event);
> +}
> +
> +static void fujitsu_mac__event_read(struct perf_event *event)
> +{
> +	fujitsu_mac_counter_update(event);
> +}
> +
> +#define MAC_PMU_FORMAT_ATTR(_name, _config)				      \
> +	(&((struct dev_ext_attribute[]) {				      \
> +		{ .attr = __ATTR(_name, 0444, device_show_string, NULL),      \
> +		  .var = (void *) _config, }				      \
> +	})[0].attr.attr)
> +
> +static struct attribute *fujitsu_mac_pmu_formats[] = {
> +	MAC_PMU_FORMAT_ATTR(event, "config:0-7"),
> +	NULL
> +};
> +
> +static const struct attribute_group fujitsu_mac_pmu_format_group = {
> +	.name = "format",
> +	.attrs = fujitsu_mac_pmu_formats,
> +};
> +
> +static ssize_t mac_pmu_event_show(struct device *dev,
> +				  struct device_attribute *attr, char *page)
> +{
> +	struct perf_pmu_events_attr *pmu_attr;
> +
> +	pmu_attr = container_of(attr, struct perf_pmu_events_attr, attr);
> +	return sysfs_emit(page, "event=0x%02llx\n", pmu_attr->id);
> +}
> +
> +#define MAC_EVENT_ATTR(_name, _id)					     \
> +	PMU_EVENT_ATTR_ID(_name, mac_pmu_event_show, _id)
> +
> +static struct attribute *fujitsu_mac_pmu_events[] = {
> +	MAC_EVENT_ATTR(cycles, MAC_EVENT_CYCLES),
> +	MAC_EVENT_ATTR(read-count, MAC_EVENT_READ_COUNT),
> +	MAC_EVENT_ATTR(read-count-request, MAC_EVENT_READ_COUNT_REQUEST),
> +	MAC_EVENT_ATTR(read-count-return, MAC_EVENT_READ_COUNT_RETURN),
> +	MAC_EVENT_ATTR(read-count-request-pftgt, MAC_EVENT_READ_COUNT_REQUEST_PFTGT),
> +	MAC_EVENT_ATTR(read-count-request-normal, MAC_EVENT_READ_COUNT_REQUEST_NORMAL),
> +	MAC_EVENT_ATTR(read-count-return-pftgt-hit, MAC_EVENT_READ_COUNT_RETURN_PFTGT_HIT),
> +	MAC_EVENT_ATTR(read-count-return-pftgt-miss, MAC_EVENT_READ_COUNT_RETURN_PFTGT_MISS),
> +	MAC_EVENT_ATTR(read-wait, MAC_EVENT_READ_WAIT),
> +	MAC_EVENT_ATTR(write-count, MAC_EVENT_WRITE_COUNT),
> +	MAC_EVENT_ATTR(write-count-write, MAC_EVENT_WRITE_COUNT_WRITE),
> +	MAC_EVENT_ATTR(write-count-pwrite, MAC_EVENT_WRITE_COUNT_PWRITE),
> +	MAC_EVENT_ATTR(memory-read-count, MAC_EVENT_MEMORY_READ_COUNT),
> +	MAC_EVENT_ATTR(memory-write-count, MAC_EVENT_MEMORY_WRITE_COUNT),
> +	MAC_EVENT_ATTR(memory-pwrite-count, MAC_EVENT_MEMORY_PWRITE_COUNT),
> +	MAC_EVENT_ATTR(ea-mac, MAC_EVENT_EA_MAC),
> +	MAC_EVENT_ATTR(ea-memory, MAC_EVENT_EA_MEMORY),
> +	MAC_EVENT_ATTR(ea-memory-mac-write, MAC_EVENT_EA_MEMORY_MAC_WRITE),
> +	MAC_EVENT_ATTR(ea-ha, MAC_EVENT_EA_HA),
I firmly maintain my opinion that if this is the only place the event 
numbers are referenced then the extra layer of macros actually makes it 
*harder* to read and follow, compared to simply:

	MAC_EVENT_ATTR(ea-ha, 0xa0),

but that is very much just one reviewer's personal opinion :)

> +	NULL
> +};
> +
> +static const struct attribute_group fujitsu_mac_pmu_events_group = {
> +	.name = "events",
> +	.attrs = fujitsu_mac_pmu_events,
> +};
> +
> +static ssize_t cpumask_show(struct device *dev,
> +			    struct device_attribute *attr, char *buf)
> +{
> +	struct mac_pmu *macpmu = to_mac_pmu(dev_get_drvdata(dev));
> +
> +	return cpumap_print_to_pagebuf(true, buf, &macpmu->cpumask);
> +}
> +static DEVICE_ATTR_RO(cpumask);
> +
> +static struct attribute *fujitsu_mac_pmu_cpumask_attrs[] = {
> +	&dev_attr_cpumask.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group fujitsu_mac_pmu_cpumask_attr_group = {
> +	.attrs = fujitsu_mac_pmu_cpumask_attrs,
> +};
> +
> +static const struct attribute_group *fujitsu_mac_pmu_attr_grps[] = {
> +	&fujitsu_mac_pmu_format_group,
> +	&fujitsu_mac_pmu_events_group,
> +	&fujitsu_mac_pmu_cpumask_attr_group,
> +	NULL
> +};
> +
> +static int fujitsu_mac_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
> +{
> +	struct mac_pmu *macpmu = hlist_entry_safe(node, struct mac_pmu, node);
> +
> +	/* If there is not a CPU/PMU association pick this CPU */
> +	if (cpumask_empty(&macpmu->cpumask))
> +		cpumask_set_cpu(cpu, &macpmu->cpumask);

You should set the IRQ affinity to the PMU CPU as well (not that you'll 
ever realistically get an overflow with 64-bit counters, but still...)

> +
> +	return 0;
> +}
> +
> +static int fujitsu_mac_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
> +{
> +	struct mac_pmu *macpmu = hlist_entry_safe(node, struct mac_pmu, node);
> +	unsigned int target;
> +
> +	if (!cpumask_test_and_clear_cpu(cpu, &macpmu->cpumask))
> +		return 0;
> +
> +	target = cpumask_any_but(cpu_online_mask, cpu);
> +	if (target >= nr_cpu_ids)
> +		return 0;
> +
> +	perf_pmu_migrate_context(&macpmu->pmu, cpu, target);
> +	cpumask_set_cpu(target, &macpmu->cpumask);

Ditto.

> +
> +	return 0;
> +}
> +
> +static int fujitsu_mac_pmu_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct acpi_device *acpi_dev;
> +	struct mac_pmu *macpmu;
> +	struct resource *memrc;
> +	char *name;
> +	int ret;
> +	u64 uid;
> +
> +	acpi_dev = ACPI_COMPANION(dev);

acpi_dev_uid_to_integer() already handles NULL, so you may as well just 
inline this like the majority of other callers do.

> +	if (!acpi_dev)
> +		return -ENODEV;
> +
> +	ret = acpi_dev_uid_to_integer(acpi_dev, &uid);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "unable to read ACPI uid\n");
> +
> +	macpmu = devm_kzalloc(dev, sizeof(*macpmu), GFP_KERNEL);
> +	if (!macpmu)
> +		return -ENOMEM;
> +
> +	name = devm_kasprintf(dev, GFP_KERNEL, "mac_iod%llu_mac%llu_ch%llu",
> +			      (uid >> 8) & 0xF, (uid >> 4) & 0xF, uid & 0xF);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	macpmu->pmu = (struct pmu) {
> +		.parent		= dev,
> +		.task_ctx_nr	= perf_invalid_context,
> +
> +		.pmu_enable	= fujitsu_mac__pmu_enable,
> +		.pmu_disable	= fujitsu_mac__pmu_disable,
> +		.event_init	= fujitsu_mac__event_init,
> +		.add		= fujitsu_mac__event_add,
> +		.del		= fujitsu_mac__event_del,
> +		.start		= fujitsu_mac__event_start,
> +		.stop		= fujitsu_mac__event_stop,
> +		.read		= fujitsu_mac__event_read,
> +
> +		.attr_groups	= fujitsu_mac_pmu_attr_grps,
> +		.capabilities	= PERF_PMU_CAP_NO_EXCLUDE | PERF_PMU_CAP_NO_INTERRUPT,
> +	};
> +
> +	macpmu->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &memrc);
> +	if (IS_ERR(macpmu->regs))
> +		return PTR_ERR(macpmu->regs);
> +
> +	fujitsu_mac__init(macpmu);
> +
> +	ret = platform_get_irq(pdev, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = devm_request_irq(dev, ret, fujitsu_mac__handle_irq, 0,
> +			       name, macpmu);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Request for IRQ failed for slice @%pa\n",

What's a slice?

> +				     &memrc->start);
> +
> +	/* Add this instance to the list used by the offline callback */
> +	ret = cpuhp_state_add_instance(mac_pmu_cpuhp_state, &macpmu->node);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Error registering hotplug");
> +
> +	ret = perf_pmu_register(&macpmu->pmu, name, -1);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "Failed to register MAC PMU\n");
You should remove the cpuhp state in the error case (but remember to use 
the _nocalls variant since you don't want to attempt to migrate anything 
in that case.)

Thanks,
Robin.

> +
> +	dev_dbg(dev, "Registered %s, type: %d\n", name, macpmu->pmu.type);
> +
> +	return 0;
> +}
> +
> +static const struct acpi_device_id fujitsu_mac_pmu_acpi_match[] = {
> +	{ "FUJI200C", },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(acpi, fujitsu_mac_pmu_acpi_match);
> +
> +static struct platform_driver fujitsu_mac_pmu_driver = {
> +	.driver = {
> +		.name = "fujitsu-mac-pmu",
> +		.acpi_match_table = fujitsu_mac_pmu_acpi_match,
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe = fujitsu_mac_pmu_probe,
> +};
> +
> +static int __init register_fujitsu_mac_pmu_driver(void)
> +{
> +	int ret;
> +
> +	/* Install a hook to update the reader CPU in case it goes offline */
> +	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
> +				      "perf/fujitsu/mac:online",
> +				      fujitsu_mac_pmu_online_cpu,
> +				      fujitsu_mac_pmu_offline_cpu);
> +	if (ret < 0)
> +		return ret;
> +
> +	mac_pmu_cpuhp_state = ret;
> +	return platform_driver_register(&fujitsu_mac_pmu_driver);
> +}
> +device_initcall(register_fujitsu_mac_pmu_driver);

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