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Date: Tue, 12 Oct 2021 08:01:49 +0000
From: Bharat Bhushan <bbhushan2@...vell.com>
To: Bharat Bhushan <bbhushan2@...vell.com>,
"will@...nel.org" <will@...nel.org>,
"mark.rutland@....com" <mark.rutland@....com>,
"robh+dt@...nel.org" <robh+dt@...nel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Bhaskara Budiredla <bbudiredla@...vell.com>
Subject: RE: [PATCH v4 3/4] perf/marvell: cn10k DDR perfmon event overflow
handling
Adding Bhaskara
> -----Original Message-----
> From: Bharat Bhushan <bbhushan2@...vell.com>
> Sent: Monday, September 20, 2021 10:38 AM
> To: will@...nel.org; mark.rutland@....com; robh+dt@...nel.org; linux-arm-
> kernel@...ts.infradead.org; devicetree@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Cc: Bharat Bhushan <bbhushan2@...vell.com>
> Subject: [PATCH v4 3/4] perf/marvell: cn10k DDR perfmon event overflow
> handling
>
> CN10k DSS h/w perfmon does not support event overflow interrupt, so periodic
> timer is being used. Each event counter is 48bit, which in worst case scenario can
> increment at maximum 5.6 GT/s. At this rate it may take many hours to overflow
> these counters. Therefore polling period for overflow is set to 100 sec, which can
> be changed using sysfs parameter.
>
> Two fixed event counters starts counting from zero on overflow, so overflow
> condition is when new count less than previous count. While eight
> programmable event counters freezes at maximum value. Also individual counter
> cannot be restarted, so need to restart all eight counters.
>
> Signed-off-by: Bharat Bhushan <bbhushan2@...vell.com>
> ---
> v3->v4:
> - No Change
>
> v2->v3:
> - uintXX_t -> uXX
>
> v1->v2:
> - No Change
>
> drivers/perf/marvell_cn10k_ddr_pmu.c | 111 +++++++++++++++++++++++++++
> 1 file changed, 111 insertions(+)
>
> diff --git a/drivers/perf/marvell_cn10k_ddr_pmu.c
> b/drivers/perf/marvell_cn10k_ddr_pmu.c
> index 9b6d5e716b94..21fccb9090c5 100644
> --- a/drivers/perf/marvell_cn10k_ddr_pmu.c
> +++ b/drivers/perf/marvell_cn10k_ddr_pmu.c
> @@ -11,6 +11,7 @@
> #include <linux/of_address.h>
> #include <linux/of_device.h>
> #include <linux/perf_event.h>
> +#include <linux/hrtimer.h>
>
> /* Performance Counters Operating Mode Control Registers */
> #define DDRC_PERF_CNT_OP_MODE_CTRL 0x8020
> @@ -127,6 +128,7 @@ struct cn10k_ddr_pmu {
> struct device *dev;
> int active_events;
> struct perf_event *events[DDRC_PERF_NUM_COUNTERS];
> + struct hrtimer hrtimer;
> };
>
> #define to_cn10k_ddr_pmu(p) container_of(p, struct cn10k_ddr_pmu, pmu)
> @@ -251,6 +253,18 @@ static const struct attribute_group *cn10k_attr_groups[]
> = {
> NULL,
> };
>
> +/* Default poll timeout is 100 sec, which is very sufficient for
> + * 48 bit counter incremented max at 5.6 GT/s, which may take many
> + * hours to overflow.
> + */
> +static unsigned long cn10k_ddr_pmu_poll_period_sec = 100;
> +module_param_named(poll_period_sec, cn10k_ddr_pmu_poll_period_sec,
> +ulong, 0644);
> +
> +static ktime_t cn10k_ddr_pmu_timer_period(void) {
> + return ms_to_ktime((u64)cn10k_ddr_pmu_poll_period_sec *
> USEC_PER_SEC);
> +}
> +
> static int ddr_perf_get_event_bitmap(int eventid, u64 *event_bitmap) {
> switch (eventid) {
> @@ -433,6 +447,10 @@ static int cn10k_ddr_perf_event_add(struct perf_event
> *event, int flags)
> pmu->active_events++;
> hwc->idx = counter;
>
> + if (pmu->active_events == 1)
> + hrtimer_start(&pmu->hrtimer, cn10k_ddr_pmu_timer_period(),
> + HRTIMER_MODE_REL_PINNED);
> +
> if (counter < DDRC_PERF_NUM_GEN_COUNTERS) {
> /* Generic counters, configure event id */
> reg_offset = DDRC_PERF_CFG(counter);
> @@ -484,6 +502,10 @@ static void cn10k_ddr_perf_event_del(struct perf_event
> *event, int flags)
> cn10k_ddr_perf_free_counter(pmu, counter);
> pmu->active_events--;
> hwc->idx = -1;
> +
> + /* Cancel timer when no events to capture */
> + if (pmu->active_events == 0)
> + hrtimer_cancel(&pmu->hrtimer);
> }
>
> static void cn10k_ddr_perf_pmu_enable(struct pmu *pmu) @@ -502,6 +524,92
> @@ static void cn10k_ddr_perf_pmu_disable(struct pmu *pmu)
> DDRC_PERF_CNT_END_OP_CTRL);
> }
>
> +static void cn10k_ddr_perf_event_update_all(struct cn10k_ddr_pmu *pmu)
> +{
> + struct hw_perf_event *hwc;
> + int i;
> +
> + for (i = 0; i < DDRC_PERF_NUM_GEN_COUNTERS; i++) {
> + if (pmu->events[i] == NULL)
> + continue;
> +
> + cn10k_ddr_perf_event_update(pmu->events[i]);
> + }
> +
> + /* Reset previous count as h/w counter are reset */
> + for (i = 0; i < DDRC_PERF_NUM_GEN_COUNTERS; i++) {
> + if (pmu->events[i] == NULL)
> + continue;
> +
> + hwc = &pmu->events[i]->hw;
> + local64_set(&hwc->prev_count, 0);
> + }
> +}
> +
> +static irqreturn_t cn10k_ddr_pmu_overflow_handler(struct cn10k_ddr_pmu
> +*pmu) {
> + struct perf_event *event;
> + struct hw_perf_event *hwc;
> + u64 prev_count, new_count;
> + u64 value;
> + int i;
> +
> + event = pmu->events[DDRC_PERF_READ_COUNTER_IDX];
> + if (event) {
> + hwc = &event->hw;
> + prev_count = local64_read(&hwc->prev_count);
> + new_count = cn10k_ddr_perf_read_counter(pmu, hwc->idx);
> +
> + /* Overflow condition is when new count less than
> + * previous count
> + */
> + if (new_count < prev_count)
> + cn10k_ddr_perf_event_update(event);
> + }
> +
> + event = pmu->events[DDRC_PERF_WRITE_COUNTER_IDX];
> + if (event) {
> + hwc = &event->hw;
> + prev_count = local64_read(&hwc->prev_count);
> + new_count = cn10k_ddr_perf_read_counter(pmu, hwc->idx);
> +
> + /* Overflow condition is when new count less than
> + * previous count
> + */
> + if (new_count < prev_count)
> + cn10k_ddr_perf_event_update(event);
> + }
> +
> + for (i = 0; i < DDRC_PERF_NUM_GEN_COUNTERS; i++) {
> + if (pmu->events[i] == NULL)
> + continue;
> +
> + value = cn10k_ddr_perf_read_counter(pmu, i);
> + if (value == DDRC_PERF_CNT_MAX_VALUE) {
> + pr_info("Counter-(%d) reached max value\n", i);
> + cn10k_ddr_perf_event_update_all(pmu);
> + cn10k_ddr_perf_pmu_disable(&pmu->pmu);
> + cn10k_ddr_perf_pmu_enable(&pmu->pmu);
> + }
> + }
> +
> + return IRQ_HANDLED;
> +}
> +
> +static enum hrtimer_restart cn10k_ddr_pmu_timer_handler(struct hrtimer
> +*hrtimer) {
> + struct cn10k_ddr_pmu *pmu = container_of(hrtimer, struct
> cn10k_ddr_pmu,
> + hrtimer);
> + unsigned long flags;
> +
> + local_irq_save(flags);
> + cn10k_ddr_pmu_overflow_handler(pmu);
> + local_irq_restore(flags);
> +
> + hrtimer_forward_now(hrtimer, cn10k_ddr_pmu_timer_period());
> + return HRTIMER_RESTART;
> +}
> +
> static int cn10k_ddr_perf_probe(struct platform_device *pdev) {
> struct cn10k_ddr_pmu *ddr_pmu;
> @@ -550,6 +658,9 @@ static int cn10k_ddr_perf_probe(struct platform_device
> *pdev)
> if (!name)
> return -ENOMEM;
>
> + hrtimer_init(&ddr_pmu->hrtimer, CLOCK_MONOTONIC,
> HRTIMER_MODE_REL);
> + ddr_pmu->hrtimer.function = cn10k_ddr_pmu_timer_handler;
> +
> ret = perf_pmu_register(&ddr_pmu->pmu, name, -1);
> if (ret)
> return ret;
> --
> 2.17.1
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