On Mon, Feb 11, 2019 at 5:19 AM Mark Rutland <mark.rutland@xxxxxxx> wrote:
>
> On Fri, Feb 08, 2019 at 06:32:39PM +0000, Frank Li wrote:
> > Add ddr performance monitor support for iMX8QXP.
> > Support below events.
> >
> > ddr0/activate/ [Kernel PMU event]
> > ddr0/axid-read/ [Kernel PMU event]
> > ddr0/axid-write/ [Kernel PMU event]
> > ddr0/cycles/ [Kernel PMU event]
> > ddr0/hp-read-credit-cnt/ [Kernel PMU event]
> > ddr0/hp-read/ [Kernel PMU event]
> > ddr0/hp-req-nodcredit/ [Kernel PMU event]
> > ddr0/hp-xact-credit/ [Kernel PMU event]
> > ddr0/load-mode/ [Kernel PMU event]
> > ddr0/lp-read-credit-cnt/ [Kernel PMU event]
> > ddr0/lp-req-nocredit/ [Kernel PMU event]
> > ddr0/lp-xact-credit/ [Kernel PMU event]
> > ddr0/mwr/ [Kernel PMU event]
> > ddr0/precharge/ [Kernel PMU event]
> > ddr0/raw-hazard/ [Kernel PMU event]
> > ddr0/read-access/ [Kernel PMU event]
> > ddr0/read-activate/ [Kernel PMU event]
> > ddr0/read-command/ [Kernel PMU event]
> > ddr0/read-cycles/ [Kernel PMU event]
> > ddr0/read-modify-write-command/ [Kernel PMU event]
> > ddr0/read-queue-depth/ [Kernel PMU event]
> > ddr0/read-write-transition/ [Kernel PMU event]
> > ddr0/read/ [Kernel PMU event]
> > ddr0/refresh/ [Kernel PMU event]
> > ddr0/selfresh/ [Kernel PMU event]
> > ddr0/wr-xact-credit/ [Kernel PMU event]
> > ddr0/write-access/ [Kernel PMU event]
> > ddr0/write-command/ [Kernel PMU event]
> > ddr0/write-credit-cnt/ [Kernel PMU event]
> > ddr0/write-cycles/ [Kernel PMU event]
> > ddr0/write-queue-depth/ [Kernel PMU event]
> > ddr0/write/
> >
> > Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> > ---
> > drivers/perf/Kconfig | 7 +
> > drivers/perf/Makefile | 1 +
> > drivers/perf/fsl_imx8_ddr_perf.c | 532 +++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 540 insertions(+)
> > create mode 100644 drivers/perf/fsl_imx8_ddr_perf.c
>
> [...]
>
> > +static void ddr_perf_event_start(struct perf_event *event, int flags)
> > +{
> > + struct ddr_pmu *pmu = to_ddr_pmu(event->pmu);
> > + struct hw_perf_event *hwc = &event->hw;
> > + int counter = hwc->idx;
> > +
> > + if (pmu->devtype->flags & DDR_CAP_AXI_ID) {
> > + if (event->attr.config == 0x41 ||
> > + event->attr.config == 0x42) {
> > + int val = event->attr.config1;
> > + writel(val, pmu->base + COUNTER_DPCR1);
> > + }
> > + }
>
> What exactly is this, and why are 0x41 and 0x42 special?
>
> This should be described in the commit message, and probably in
> Documentation/perf/, given this is unusual.
>
> > +
> > + local64_set(&hwc->prev_count, 0);
> > +
> > + ddr_perf_event_enable(pmu, event->attr.config, counter, true);
> > + /*
> > + * If the cycles counter wasn't explicitly selected,
> > + * we will enable it now.
> > + */
> > + if (counter > 0 && !pmu->cycles_active)
> > + ddr_perf_event_enable(pmu, EVENT_CYCLES_ID,
> > + EVENT_CYCLES_COUNTER, true);
> > +}
>
> Why do we need to enable the cycle counter?
>
> If this is a requirement, it should be described in the commit message.
>
> > +static int ddr_perf_event_add(struct perf_event *event, int flags)
> > +{
> > + struct ddr_pmu *pmu = to_ddr_pmu(event->pmu);
> > + struct hw_perf_event *hwc = &event->hw;
> > + int counter;
> > + int cfg = event->attr.config;
> > +
> > + counter = ddr_perf_alloc_counter(pmu, cfg);
> > + if (counter < 0) {
> > + dev_warn(pmu->dev, "There are not enough counters\n");
> > + return -EOPNOTSUPP;
> > + }
>
> This should be dev_dbg(), not dev_warn().
>
> > +static irqreturn_t ddr_perf_irq_handler(int irq, void *p)
> > +{
> > + int i;
> > + u8 reg;
> > + int val;
> > + int counter;
> > + struct ddr_pmu *pmu = (struct ddr_pmu *) p;
> > + struct perf_event *event;
> > +
> > + /*
> > + * The cycles counter has overflowed. Update all of the local counter
> > + * values, then reset the cycles counter, so the others can continue
> > + * counting.
> > + */
>
> Does the interrupt only fire when the cycle counter overflows?
>
> i.e. there is no way to detect when other counters overflow?
>
> > + for (i = 0; i <= pmu->total_events; i++) {
> > + if (pmu->active_events[i] != NULL) {
> > + event = pmu->active_events[i];
> > + counter = event->hw.idx;
> > + reg = counter * 4 + COUNTER_CNTL;
> > + val = readl(pmu->base + reg);
> > + ddr_perf_event_update(event);
> > + if (val & CNTL_OVER) {
> > + /* Clear counter, then re-enable it. */
> > + ddr_perf_event_enable(pmu, event->attr.config,
> > + counter, true);
> > + /* Update event again to reset prev_count */
> > + ddr_perf_event_update(event);
> > + }
> > + }
> > + }
>
> Depending on how events are added/removed, they may not be contiguous,
> so it isn't correct to use total_events here. You need to check all
> NUM_COUNTER slots.
>
> Please also avoid nesting by using an early continue, e.g.
>
> for (i = 0; i < NUM_COUNTER; i++) {
> if (!pmu->active_events[i])
> continue;
>
> event = pmu->active_events[i];
> counter = event->hw.idx;
>
> ...
> }
>
> > +
> > + /*
> > + * Reset the cycles counter regardless if it was explicitly
> > + * enabled or not.
> > + */
> > + ddr_perf_event_enable(pmu, EVENT_CYCLES_ID,
> > + EVENT_CYCLES_COUNTER, true);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +static int ddr_perf_probe(struct platform_device *pdev)
> > +{
> > + struct ddr_pmu *pmu;
> > + struct device_node *np;
> > + void __iomem *base;
> > + struct resource *iomem;
> > + char *name;
> > + int num;
> > + int ret;
> > + u32 irq;
> > + const struct of_device_id *of_id =
> > + of_match_device(imx_ddr_pmu_dt_ids, &pdev->dev);
> > +
> > + iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > + base = devm_ioremap_resource(&pdev->dev, iomem);
> > + if (IS_ERR(base)) {
> > + ret = PTR_ERR(base);
> > + return ret;
> > + }
> > +
> > + np = pdev->dev.of_node;
> > +
> > + pmu = kzalloc(sizeof(*pmu), GFP_KERNEL);
> > + if (!pmu)
> > + return -ENOMEM;
> > +
> > + num = ddr_perf_init(pmu, base, &pdev->dev);
> > + name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "ddr%d", num);
> > +
> > + pmu->devtype = (struct fsl_ddr_devtype_data *)of_id->data;
> > +
> > + cpumask_set_cpu(smp_processor_id(), &pmu->cpu);
>
> This will need a hotplug callback to handle context migration.
Thanks, Other comments I known how to change.
this is global event, why need take care cpu hotplugs.
Do you have sample code how to handle hotplug callback?
best regards
Frank Li
>
> > + ret = perf_pmu_register(&(pmu->pmu), name, -1);
> > + if (ret)
> > + goto ddr_perf_err;
> > +
> > + /* Request irq */
> > + irq = of_irq_get(np, 0);
> > + if (irq < 0) {
> > + pr_err("Failed to get irq: %d", irq);
> > + goto ddr_perf_err;
> > + }
> > +
> > + ret = devm_request_threaded_irq(&pdev->dev, irq,
> > + ddr_perf_irq_handler, NULL,
> > + IRQF_TRIGGER_RISING | IRQF_ONESHOT,
> > + DDR_PERF_DEV_NAME,
>
> This should not be a threaded IRQ. Your code implicitly relies on mutual
> exclusion between the IRQ handler and other code (e.g. when the perf
> core code disables interrupts).
>
> Thanks,
> Mark.
