Subject: Re: [PATCH v2 6/7]powerpc/powernv: generic nest pmu event functions

From: Sukadev Bhattiprolu <[email-masked]>
Date: Mon, 22 Jun 2015 18:49:49 -0700

Madhavan Srinivasan [[email-masked]] wrote:
| From: Madhavan Srinivasan <[email-masked]>
| Subject: [PATCH v2 6/7]powerpc/powernv: generic nest pmu event functions
| 
| Add generic format attribute and set of generic nest pmu related
| event functions to be used by each nest pmu. Add code to register nest pmus.
| 
| Cc: Michael Ellerman <[email-masked]>
| Cc: Benjamin Herrenschmidt <[email-masked]>
| Cc: Paul Mackerras <[email-masked]>
| Cc: Anton Blanchard <[email-masked]>
| Cc: Sukadev Bhattiprolu <[email-masked]>
| Cc: Anshuman Khandual <[email-masked]>
| Cc: Stephane Eranian <[email-masked]>
| Signed-off-by: Madhavan Srinivasan <[email-masked]>
| ---
|  arch/powerpc/perf/nest-pmu.c | 109 +++++++++++++++++++++++++++++++++++++++++++
|  1 file changed, 109 insertions(+)
| 
| diff --git a/arch/powerpc/perf/nest-pmu.c b/arch/powerpc/perf/nest-pmu.c
| index 8fad2d9..a662c14 100644
| --- a/arch/powerpc/perf/nest-pmu.c
| +++ b/arch/powerpc/perf/nest-pmu.c
| @@ -13,6 +13,108 @@
|  static struct perchip_nest_info p8_perchip_nest_info[P8_MAX_CHIP];
|  static struct nest_pmu *per_nest_pmu_arr[P8_MAX_NEST_PMUS];
| 
| +PMU_FORMAT_ATTR(event, "config:0-20");
| +struct attribute *p8_nest_format_attrs[] = {
| +	&format_attr_event.attr,
| +	NULL,
| +};
| +
| +struct attribute_group p8_nest_format_group = {
| +	.name = "format",
| +	.attrs = p8_nest_format_attrs,
| +};

Could this be included in previous/separate patch? That way,
this patch could focus on just registering the nest-pmu.

| +
| +static int p8_nest_event_init(struct perf_event *event)
| +{
| +	int chip_id;
| +
| +	if (event->attr.type != event->pmu->type)
| +		return -ENOENT;
| +
| +	/* Sampling not supported yet */
| +	if (event->hw.sample_period)
| +		return -EINVAL;
| +
| +	/* unsupported modes and filters */
| +	if (event->attr.exclude_user   ||
| +	    event->attr.exclude_kernel ||
| +	    event->attr.exclude_hv     ||
| +	    event->attr.exclude_idle   ||
| +	    event->attr.exclude_host   ||
| +	    event->attr.exclude_guest)
| +		return -EINVAL;
| +
| +	if (event->cpu < 0)
| +		return -EINVAL;
| +
| +	chip_id = topology_physical_package_id(event->cpu);
| +	event->hw.event_base = event->attr.config +
| +				p8_perchip_nest_info[chip_id].vbase;
| +
| +	return 0;
| +}
| +
| +static void p8_nest_read_counter(struct perf_event *event)
| +{
| +	u64 *addr;
| 

Define as uint64_t so we can eliminate one cast below? Would also
be consistent with p8_nest_perf_event_update().

| 
| +	u64 data = 0;
| +
| +	addr = (u64 *)event->hw.event_base;
| +	data = __be64_to_cpu((uint64_t)*addr);
| +	local64_set(&event->hw.prev_count, data);
| +}
| +
| +static void p8_nest_perf_event_update(struct perf_event *event)
| +{
| +	u64 counter_prev, counter_new, final_count;
| +	uint64_t *addr;
| +
| +	addr = (u64 *)event->hw.event_base;

uint64_t *?

| +	counter_prev = local64_read(&event->hw.prev_count);
| +	counter_new = __be64_to_cpu((uint64_t)*addr);

Redundant cast? addr is already uint64_t *?

| +	final_count = counter_new - counter_prev;
| +
| +	local64_set(&event->hw.prev_count, counter_new);
| +	local64_add(final_count, &event->count);
| +}
| +
| +static void p8_nest_event_start(struct perf_event *event, int flags)
| +{

Check PERF_EF_RELOAD before reloading?

| +	event->hw.state = 0;
| +	p8_nest_read_counter(event);
| +}
| +
| +static void p8_nest_event_stop(struct perf_event *event, int flags)
| +{

Check PERF_EF_UPDATE when stopping?

| +	p8_nest_perf_event_update(event);
| +}
| +
| +static int p8_nest_event_add(struct perf_event *event, int flags)
| +{

Check PERF_EF_START flags before starting the counter on an ->add()?

| +	p8_nest_event_start(event, flags);
| +	return 0;
| +}
| +
| +/*
| + * Populate pmu ops in the structure
| + */
| +static int update_pmu_ops(struct nest_pmu *pmu)
| +{
| +	if (!pmu)
| +		return -EINVAL;
| +
| +	pmu->pmu.task_ctx_nr = perf_invalid_context;
| +	pmu->pmu.event_init = p8_nest_event_init;
| +	pmu->pmu.add = p8_nest_event_add;
| +	pmu->pmu.del = p8_nest_event_stop;
| +	pmu->pmu.start = p8_nest_event_start;
| +	pmu->pmu.stop = p8_nest_event_stop;
| +	pmu->pmu.read = p8_nest_perf_event_update;
| +	pmu->pmu.attr_groups = pmu->attr_groups;
| +
| +	return 0;
| +}
| +
|  /*
|   * Populate event name and string in attribute
|   */
| @@ -106,6 +208,7 @@ static int nest_pmu_create(struct device_node *dev, int pmu_index)
|  			/* Save the name to register the PMU with it */
|  			sprintf(buf, "Nest_%s", (char *)pp->value);
|  			pmu_ptr->pmu.name = (char *)buf;
| +			pmu_ptr->attr_groups[1] = &p8_nest_format_group;
|  		}
| 
|  		/* Skip these, we dont need it */
| @@ -179,6 +282,12 @@ static int nest_pmu_create(struct device_node *dev, int pmu_index)
|  		(struct ppc64_nest_ima_events *)p8_events_arr,
|  							idx, pmu_ptr);
| 
| +	update_pmu_ops(pmu_ptr);
| +
| +	/* Register the pmu */
| +	perf_pmu_register(&pmu_ptr->pmu, pmu_ptr->pmu.name, -1);

There is a small chance that perf_pmu_register() can fail.

| +	printk(KERN_INFO "Nest PMU %s Registered\n", pmu_ptr->pmu.name);
| +
|  	return 0;
|  }
| 
| -- 
| 1.9.1
|