Re: [PATCH v4 1/2] perf: starfive: Add StarLink PMU support

From: Ji Sheng Teoh
Date: Thu Nov 30 2023 - 03:32:35 EST

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In reply to: Jonathan Cameron: "Re: [PATCH v4 1/2] perf: starfive: Add StarLink PMU support"
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On Wed, 29 Nov 2023 11:02:38 +0000
Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote:

> On Fri, 17 Nov 2023 00:23:29 +0800
> Ji Sheng Teoh <jisheng.teoh@xxxxxxxxxxxxxxxx> wrote:
>
> > This patch adds support for StarFive's StarLink PMU (Performance
> > Monitor Unit). StarLink PMU integrates one or more CPU cores with
> > a shared L3 memory system. The PMU supports overflow interrupt,
> > up to 16 programmable 64bit event counters, and an independent
> > 64bit cycle counter. StarLink PMU is accessed via MMIO.
> >
> > Example Perf stat output:
> > [root@user]# perf stat -a -e /starfive_starlink_pmu/cycles/ \
> > -e /starfive_starlink_pmu/read_miss/ \
> > -e /starfive_starlink_pmu/read_hit/ \
> > -e /starfive_starlink_pmu/release_request/ \
> > -e /starfive_starlink_pmu/write_hit/ \
> > -e /starfive_starlink_pmu/write_miss/ \
> > -e /starfive_starlink_pmu/write_request/ \
> > -e /starfive_starlink_pmu/writeback/ \
> > -e /starfive_starlink_pmu/read_request/ \
> > -- openssl speed rsa2048
> > Doing 2048 bits private rsa's for 10s: 5 2048 bits private RSA's in
> > 2.84s
> > Doing 2048 bits public rsa's for 10s: 169 2048 bits public RSA's in
> > 2.42s
> > version: 3.0.11
> > built on: Tue Sep 19 13:02:31 2023 UTC
> > options: bn(64,64)
> > CPUINFO: N/A
> > sign verify sign/s verify/s
> > rsa 2048 bits 0.568000s 0.014320s 1.8 69.8
> > /////////
> > Performance counter stats for 'system wide':
> >
> > 649991998 starfive_starlink_pmu/cycles/
> > 1009690 starfive_starlink_pmu/read_miss/
> > 1079750 starfive_starlink_pmu/read_hit/
> > 2089405 starfive_starlink_pmu/release_request/
> > 129 starfive_starlink_pmu/write_hit/
> > 70 starfive_starlink_pmu/write_miss/
> > 194 starfive_starlink_pmu/write_request/
> > 150080 starfive_starlink_pmu/writeback/
> > 2089423 starfive_starlink_pmu/read_request/
> >
> > 27.062755678 seconds time elapsed
> >
> > Signed-off-by: Ji Sheng Teoh <jisheng.teoh@xxxxxxxxxxxxxxxx>
> Hi. Some drive by comments inline.
>
> Mostly concern being consistent with error handling.
>
> Documentation needed.
> Documentation/admin-guide/perf

Sure, will include it.
>
> Note I've not looked at perf state machine as would need to remind
> myself how that stuff works. So this is all generic driver handling
> stuff rather than perf specific.
>
> Thanks,
>
> Jonathan
>
> > ---
> > diff --git a/drivers/perf/starfive_starlink_pmu.c
> > b/drivers/perf/starfive_starlink_pmu.c new file mode 100644
> > index 000000000000..272896ab1ade
> > --- /dev/null
> > +++ b/drivers/perf/starfive_starlink_pmu.c
> > @@ -0,0 +1,654 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * StarFive's StarLink PMU driver
> > + *
> > + * Copyright (C) 2023 StarFive Technology Co., Ltd.
> > + *
> > + * Author: Ji Sheng Teoh <jisheng.teoh@xxxxxxxxxxxxxxxx>
> > + *
> > + */
> > +
> > +#define STARLINK_PMU_PDEV_NAME "starfive_starlink_pmu"
> > +#define pr_fmt(fmt) STARLINK_PMU_PDEV_NAME ": " fmt
> > +
> > +#include <linux/bitmap.h>
> > +#include <linux/cpu_pm.h>
> > +#include <linux/io.h>
> > +#include <linux/irq.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/of_device.h>
>
> Why? Probably want mod_devicetable.h

Ok, that is a better option. Thanks
>
> > +#include <linux/perf_event.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/sysfs.h>
> > +
> > +#define STARLINK_PMU_MAX_COUNTERS 64
> > +#define STARLINK_PMU_NUM_COUNTERS 16
> > +#define STARLINK_PMU_IDX_CYCLE_COUNTER 63
> > +
> > +#define STARLINK_PMU_EVENT_SELECT 0x060
> > +#define STARLINK_PMU_EVENT_COUNTER 0x160
> > +#define STARLINK_PMU_COUNTER_MASK
> > GENMASK_ULL(63, 0) +#define STARLINK_PMU_CYCLE_COUNTER
> > 0x058 +
> > +#define STARLINK_PMU_CONTROL 0x040
> > +#define STARLINK_PMU_GLOBAL_ENABLE BIT(0)
> > +
> > +#define STARLINK_PMU_INTERRUPT_ENABLE 0x050
> > +#define STARLINK_PMU_COUNTER_OVERFLOW_STATUS 0x048
> > +#define STARLINK_PMU_CYCLE_OVERFLOW_MASK BIT(63)
> > +
> > +#define CYCLES 0x058
>
> Prefix these. Highly likely to have namespace clashes.
> STARLINK_CYCLES etc

Ok, that makes sense. Will make the change.
>
> > +#define CACHE_READ_REQUEST 0x04000701
> > +#define CACHE_WRITE_REQUEST 0x03000001
> > +#define CACHE_RELEASE_REQUEST 0x0003e001
> > +#define CACHE_READ_HIT 0x00901202
> > +#define CACHE_READ_MISS 0x04008002
> > +#define CACHE_WRITE_HIT 0x006c0002
> > +#define CACHE_WRITE_MISS 0x03000002
> > +#define CACHE_WRITEBACK 0x00000403
> > +
> > +#define to_starlink_pmu(p) (container_of(p, struct starlink_pmu,
> > pmu)) +
> > +#define STARLINK_FORMAT_ATTR(_name, _config)
> > \
> > + (&((struct dev_ext_attribute[]) {
> > \
> > + { .attr = __ATTR(_name, 0444,
> > starlink_pmu_sysfs_format_show, NULL), \
> > + .var = (void *)_config, }
> > \
> > + })[0].attr.attr)
> > +
> > +#define STARLINK_EVENT_ATTR(_name, _id)
> > \
> > + PMU_EVENT_ATTR_ID(_name, starlink_pmu_sysfs_event_show,
> > _id) +
> > +#define BIT_IS_SET(nr, bit) (((nr) >> (bit)) & 0x1)
>
> Not sure this macro is worth having. Mostly used as boolean, so
> nr & BIT(bit) inline would do the job.
>
Ok, will revise it based on your suggestion.

> > +
> > +struct starlink_hw_events {
> > + struct perf_event
> > *events[STARLINK_PMU_MAX_COUNTERS];
> > + DECLARE_BITMAP(used_mask, STARLINK_PMU_MAX_COUNTERS);
> > +};
> > +
> > +struct starlink_pmu {
> > + struct pmu pmu;
> > + struct starlink_hw_events __percpu
> > *hw_events;
> > + struct hlist_node node;
> > + struct notifier_block
> > starlink_pmu_pm_nb;
> > + void __iomem
> > *pmu_base;
> > + cpumask_t cpumask;
> > + int irq;
> > +};
> > +
> > +/* Formats Attr */
> > +static ssize_t
> > +starlink_pmu_sysfs_format_show(struct device *dev,
> > + struct device_attribute *attr,
> > + char *buf)
> > +{
> > + struct dev_ext_attribute *eattr = container_of(attr,
> > + struct
> > dev_ext_attribute, attr); +
> > + return sysfs_emit(buf, "%s\n", (char *)eattr->var);
> > +}
> > +
> > +static struct attribute *starlink_pmu_format_attrs[] = {
> > + STARLINK_FORMAT_ATTR(event, "config:0-31"),
> > + NULL,
> As below.
>
> > +};
> > +
> > +static const struct attribute_group starlink_pmu_format_attr_group
> > = {
> > + .name = "format",
> > + .attrs = starlink_pmu_format_attrs,
> > +};
> > +
> > +/* Events Attr */
>
> These comments don't really add much given that's easy to see from
> code. It's rare that 'structure' comments describing where things are
> in code are actually useful in kernel drivers. They tend to be there
> in example code to indicate what is needed, but don't keep them!
>
Ok, will drop them.
>
> > +static ssize_t
> > +starlink_pmu_sysfs_event_show(struct device *dev,
> > + struct device_attribute *attr,
> > + char *buf)
> > +{
> > + struct perf_pmu_events_attr *eattr = container_of(attr,
> > + struct
> > perf_pmu_events_attr, attr); +
> > + return sysfs_emit(buf, "event=0x%02llx\n", eattr->id);
> > +}
> > +
> > +static struct attribute *starlink_pmu_event_attrs[] = {
> > + STARLINK_EVENT_ATTR(cycles, CYCLES),
> > + STARLINK_EVENT_ATTR(read_request, CACHE_READ_REQUEST),
> > + STARLINK_EVENT_ATTR(write_request, CACHE_WRITE_REQUEST),
> > + STARLINK_EVENT_ATTR(release_request,
> > CACHE_RELEASE_REQUEST),
> > + STARLINK_EVENT_ATTR(read_hit, CACHE_READ_HIT),
> > + STARLINK_EVENT_ATTR(read_miss, CACHE_READ_MISS),
> > + STARLINK_EVENT_ATTR(write_hit, CACHE_WRITE_HIT),
> > + STARLINK_EVENT_ATTR(write_miss, CACHE_WRITE_MISS),
> > + STARLINK_EVENT_ATTR(writeback, CACHE_WRITEBACK),
> > + NULL,
>
> As below.
>
> > +};
> > +
> > +static const struct attribute_group starlink_pmu_events_attr_group
> > = {
> > + .name = "events",
> > + .attrs = starlink_pmu_event_attrs,
> > +};
> > +
> > +/* Cpumask Attr */
> > +static ssize_t
> > +cpumask_show(struct device *dev, struct device_attribute *attr,
> > char *buf) +{
> > + struct starlink_pmu *starlink_pmu =
> > to_starlink_pmu(dev_get_drvdata(dev)); +
> > + return cpumap_print_to_pagebuf(true, buf,
> > &starlink_pmu->cpumask); +}
> > +
> > +static DEVICE_ATTR_RO(cpumask);
> > +
> > +static struct attribute *starlink_pmu_cpumask_attrs[] = {
> > + &dev_attr_cpumask.attr,
> > + NULL,
>
> As below.
>
> > +};
> > +
> > +static const struct attribute_group
> > starlink_pmu_cpumask_attr_group = {
> > + .attrs = starlink_pmu_cpumask_attrs,
> > +};
> > +
> > +static const struct attribute_group *starlink_pmu_attr_groups[] = {
> > + &starlink_pmu_format_attr_group,
> > + &starlink_pmu_events_attr_group,
> > + &starlink_pmu_cpumask_attr_group,
> > + NULL,
>
> No comma after NULL terminator as we can't add anything there anyway.
>
Ok, will drop them.

> > +};
>
>
> > +
> > +static void starlink_pmu_counter_stop(struct perf_event *event,
> > + struct starlink_pmu
> > *starlink_pmu) +{
> > + struct hw_perf_event *hwc = &event->hw;
> > + int idx = event->hw.idx;
> > + u64 val;
> > +
> > + /* Stop counter */
>
> Pretty obvious that clearing global enable stops the counter.
> Perhaps review comments and remove any that are obvious from the code.
> Such comments add little value and can be a maintenance problem.
>
Ok, will review again and drop those comments that are obvious.

> > + val = readq(starlink_pmu->pmu_base + STARLINK_PMU_CONTROL);
> > + val &= ~STARLINK_PMU_GLOBAL_ENABLE;
> > + writeq(val, starlink_pmu->pmu_base + STARLINK_PMU_CONTROL);
> > +
> > + /* Disable counter overflow interrupt */
> > + val = readq(starlink_pmu->pmu_base +
> > STARLINK_PMU_INTERRUPT_ENABLE);
> > + if (hwc->config == CYCLES)
> > + val &= ~STARLINK_PMU_CYCLE_OVERFLOW_MASK;
> > + else
> > + val &= ~(1 << idx);
> > +
> > + writeq(val, starlink_pmu->pmu_base +
> > STARLINK_PMU_INTERRUPT_ENABLE); +}
>
>
>
> > +static bool starlink_pmu_validate_event_group(struct perf_event
> > *event) +{
> > + struct perf_event *leader = event->group_leader;
> > + struct perf_event *sibling;
> > + int counter = 1;
> > +
> > + /*
> > + * Ensure hardware events in the group are on the same PMU,
> > + * software events are acceptable.
> > + */
> > + if (event->group_leader->pmu != event->pmu &&
> > + !is_software_event(event->group_leader))
> > + return false;
> > +
> > + for_each_sibling_event(sibling, leader) {
> > + if (sibling->pmu != event->pmu &&
> > !is_software_event(sibling))
> > + return false;
> > +
> > + counter += 1;
>
> counter++;

Ok, will amend.
>
> > + }
> > + /*
> > + * Limit the number of requested counter to
> > + * counter available on the HW.
> > + */
> > + return counter <= STARLINK_PMU_NUM_COUNTERS;
> > +}
> > +
>
> ...
>
> > +
> > +static irqreturn_t starlink_pmu_handle_irq(int irq_num, void *data)
> > +{
> > + struct starlink_pmu *starlink_pmu = data;
> > + struct starlink_hw_events *hw_events =
> > +
> > this_cpu_ptr(starlink_pmu->hw_events);
>
> Odd alignment. I'd put it one tab more than struct.

Ok, will realign them.
>
> > + bool handled = false;
> > + int idx;
> > + u64 overflow_status;
> > +
> > + for (idx = 0; idx < STARLINK_PMU_MAX_COUNTERS; idx++) {
> > + struct perf_event *event = hw_events->events[idx];
> > +
> > + overflow_status = readq(starlink_pmu->pmu_base +
> > +
> > STARLINK_PMU_COUNTER_OVERFLOW_STATUS);
> > + if (!BIT_IS_SET(overflow_status, idx))
> > + continue;
> > +
> > + /* Clear event counter overflow interrupt */
> > + writeq(1 << idx, starlink_pmu->pmu_base +
> > + STARLINK_PMU_COUNTER_OVERFLOW_STATUS);
> > +
> > + if (!event)
> > + continue;
> If you get here and !event. Is it a bug, or something valid?
> Maybe a comment if it's valid. Otherwise an error print might make
> sense.
>
They should have appear earlier right before reading the overflow
status, and continue next bit in the case where event is not valid.
Will fix it.

> > +
> > + starlink_pmu_update(event);
> > + starlink_pmu_set_event_period(event);
> > + handled = true;
> > + }
> > + return IRQ_RETVAL(handled);
> > +}
> > +
> > +static int starlink_setup_irqs(struct starlink_pmu *starlink_pmu,
> > + struct platform_device *pdev)
> > +{
> > + int ret, irq;
> > +
> > + irq = platform_get_irq(pdev, 0);
> > + if (irq < 0)
> > + return -EINVAL;
> > +
> > + ret = devm_request_irq(&pdev->dev, irq,
> > starlink_pmu_handle_irq,
> > + 0, STARLINK_PMU_PDEV_NAME,
> > starlink_pmu);
> > + if (ret) {
> > + dev_warn(&pdev->dev, "Failed to request IRQ %d\n",
> > irq);
> > + return ret;
>
> return dev_err_probe(...)

Will pass this ret back to probe() to handle instead.
>
> > + }
> > +
> > + starlink_pmu->irq = irq;
> > +
> > + return 0;
> > +}
> > +
> > +#ifdef CONFIG_CPU_PM
> > +static int starlink_pmu_pm_notify(struct notifier_block *b,
> > + unsigned long cmd, void *v)
> > +{
> > + struct starlink_pmu *starlink_pmu = container_of(b, struct
> > starlink_pmu,
> > +
> > starlink_pmu_pm_nb);
>
> Compiler can probably figure out this isn't used. But if not
> if (!IS_ENABLED(CONFIG_CPU_PM))
> return 0;
>
> will allow the compiler to definitely remove the code.

Good info, thanks for the suggestion. Will use
'if (IS_ENABLED(CONFIG_CPU_PM))' in place of '#ifdef CONFIG_CPU_PM'.

>
> > + struct starlink_hw_events *hw_events =
> > +
> > this_cpu_ptr(starlink_pmu->hw_events);
> > + int enabled = bitmap_weight(hw_events->used_mask,
> > + STARLINK_PMU_MAX_COUNTERS);
> > + struct perf_event *event;
> > + int idx;
> > +
> > + if (!enabled)
> > + return NOTIFY_OK;
> > +
> > + for (idx = 0; idx < STARLINK_PMU_MAX_COUNTERS; idx++) {
> > + event = hw_events->events[idx];
> > + if (!event)
> > + continue;
> > +
> > + switch (cmd) {
> > + case CPU_PM_ENTER:
> > + /* Stop and update the counter */
> > + starlink_pmu_stop(event, PERF_EF_UPDATE);
> > + break;
> > + case CPU_PM_EXIT:
> > + case CPU_PM_ENTER_FAILED:
> > + /* Restore and enable the counter */
> > + starlink_pmu_start(event, PERF_EF_RELOAD);
> > + break;
> > + default:
> > + break;
> > + }
> > + }
> > +
> > + return NOTIFY_OK;
> > +}
> > +
> > +static int starlink_pmu_pm_register(struct starlink_pmu
> > *starlink_pmu) +{
> > + starlink_pmu->starlink_pmu_pm_nb.notifier_call =
> > starlink_pmu_pm_notify;
> > + return
> > cpu_pm_register_notifier(&starlink_pmu->starlink_pmu_pm_nb);
> Stubbed out as below.
>
> > +}
> > +
> > +static void starlink_pmu_pm_unregister(struct starlink_pmu
> > *starlink_pmu) +{
> > +
> > cpu_pm_unregister_notifier(&starlink_pmu->starlink_pmu_pm_nb);
>
> stubbed out in header so no need to protect with ifdef.
> Compiler will probably remove it anyway.
>
Ok, will fix.

> > +}
> > +#else
> > +static inline int
> > +starlink_pmu_pm_register(struct starlink_pmu *starlink_pmu) {
> > return 0; } +static inline void
> > +starlink_pmu_pm_unregister(struct starlink_pmu *starlink_pmu) { }
> > +#endif
> > +
> > +static void starlink_pmu_destroy(struct starlink_pmu *starlink_pmu)
> > +{
> > + starlink_pmu_pm_unregister(starlink_pmu);
> > +
> > cpuhp_state_remove_instance(CPUHP_AP_PERF_RISCV_STARFIVE_STARLINK_ONLINE,
> > + &starlink_pmu->node);
> > +}
> > +
> > +static int starlink_pmu_probe(struct platform_device *pdev)
> > +{
> > + struct starlink_pmu *starlink_pmu;
> > + struct starlink_hw_events *hw_events;
> > + struct resource *res;
> > + int cpuid, i, ret;
> > +
> > + starlink_pmu = devm_kzalloc(&pdev->dev,
> > sizeof(*starlink_pmu), GFP_KERNEL);
> > + if (!starlink_pmu)
> > + return -ENOMEM;
> > +
> > + starlink_pmu->pmu_base =
> > +
> > devm_platform_get_and_ioremap_resource(pdev, 0, &res);
> > + if (IS_ERR(starlink_pmu->pmu_base))
> > + return PTR_ERR(starlink_pmu->pmu_base);
> > +
> > + ret = starlink_setup_irqs(starlink_pmu, pdev);
>
> Handle ret You are printing a warning so I'd assume it's a failure
> to probe case, not something ignored.
>
Missed that, will fix it.

>
> > +
> > + ret =
> > cpuhp_state_add_instance(CPUHP_AP_PERF_RISCV_STARFIVE_STARLINK_ONLINE,
> > + &starlink_pmu->node);
> > + if (ret)
>
> Not dropped in error paths.

Ok, will fix it.
>
> > + return ret;
> > +
> > + ret = starlink_pmu_pm_register(starlink_pmu);
> > + if (ret)
> > + starlink_pmu_destroy(starlink_pmu);
>
> This calls starlink_pmu_pm_unregister()
> That should not be necessary as every function should be designed to
> have no side effects on error return.
>
Ok, will fix it.

> > +
> > + starlink_pmu->hw_events = alloc_percpu_gfp(struct
> > starlink_hw_events,
> > + GFP_KERNEL);
> > + if (!starlink_pmu->hw_events) {
> > + pr_info("Failed to allocate per-cpu PMU data.\n");
> > + kfree(starlink_pmu);
>
> Inconsistent error handling. Before and aftre this you call
> starlink_pmu_destroy() but not here.
>
Ok, will rectify it.

> > + return -ENOMEM;
> > + }
> > +
> > + for_each_possible_cpu(cpuid) {
> > + hw_events = per_cpu_ptr(starlink_pmu->hw_events,
> > cpuid);
> > + for (i = 0; i < STARLINK_PMU_MAX_COUNTERS; i++)
> > + hw_events->events[i] = NULL;
> > + }
> > +
> > + starlink_pmu->pmu = (struct pmu) {
> > + .task_ctx_nr = perf_invalid_context,
> > + .event_init = starlink_pmu_event_init,
> > + .add = starlink_pmu_add,
> > + .del = starlink_pmu_del,
> > + .start = starlink_pmu_start,
> > + .stop = starlink_pmu_stop,
> > + .read = starlink_pmu_update,
> > + .attr_groups = starlink_pmu_attr_groups,
> > + };
> > +
> > + ret = perf_pmu_register(&starlink_pmu->pmu,
> > STARLINK_PMU_PDEV_NAME, -1);
> > + if (ret)
> > + starlink_pmu_destroy(starlink_pmu);
> > +
> > + dev_info(&pdev->dev, "Registered StarFive's StarLink
> > PMU\n");
>
> Noise. Don't print to the log when there are many other ways to find
> this out.
>
Ok, will drop it.

> > +
> > + return ret;
> > +}
> > +
> > +static const struct of_device_id starlink_pmu_of_match[] = {
> > + { .compatible = "starfive,jh8100-starlink-pmu", },
> > + {},
>
> No need for comma after a 'terminator' as nothing can come after it.
>
Ok, will drop it.

> > +};
> > +MODULE_DEVICE_TABLE(of, starlink_pmu_of_match);
>
> > +device_initcall(starlink_pmu_init);
> > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> > index d305db70674b..6d9eb70c13d4 100644
> > --- a/include/linux/cpuhotplug.h
> > +++ b/include/linux/cpuhotplug.h
> > @@ -219,6 +219,7 @@ enum cpuhp_state {
> > CPUHP_AP_PERF_X86_CQM_ONLINE,
> > CPUHP_AP_PERF_X86_CSTATE_ONLINE,
> > CPUHP_AP_PERF_X86_IDXD_ONLINE,
> > + CPUHP_AP_PERF_RISCV_STARFIVE_STARLINK_ONLINE,
> Can you use CPUHP_AP_ONLINE_DYN?
>
> Moves it a bit later in the sequence but it often works for perf
> drivers.
>
Yup, that should work as well. Will use CPUHP_AP_ONLINE_DYN instead.

> > CPUHP_AP_PERF_S390_CF_ONLINE,
> > CPUHP_AP_PERF_S390_SF_ONLINE,
> > CPUHP_AP_PERF_ARM_CCI_ONLINE,
>

Thanks for reviewing Jonathan.

Thanks,

Ji Sheng

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