linux-kernel - Re: [PATCH v4 10/11] drivers: perf: hisi: Handle counter overflow IRQ in MN PMU

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Date:   Mon, 20 Feb 2017 11:29:19 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Anurup M <anurupvasu@...il.com>
Cc:     will.deacon@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, anurup.m@...wei.com,
        zhangshaokun@...ilicon.com, tanxiaojun@...wei.com,
        xuwei5@...ilicon.com, sanil.kumar@...ilicon.com,
        john.garry@...wei.com, gabriele.paoloni@...wei.com,
        shiju.jose@...wei.com, huangdaode@...ilicon.com,
        linuxarm@...wei.com, dikshit.n@...wei.com, shyju.pv@...wei.com
Subject: Re: [PATCH v4 10/11] drivers: perf: hisi: Handle counter overflow
 IRQ in MN PMU

Hi,

On Sun, Feb 19, 2017 at 01:51:22PM -0500, Anurup M wrote:
> +static irqreturn_t hisi_pmu_mn_isr(int irq, void *dev_id)
> +{
> +	struct hisi_pmu *mn_pmu = dev_id;
> +	struct hisi_mn_data *mn_data = mn_pmu->hwmod_data;
> +	struct hisi_djtag_client *client = mn_data->client;
> +	struct perf_event *event;
> +	u32 module_id = GET_MODULE_ID(mn_data);
> +	unsigned long flags;
> +	u32 value = 0;
> +	int bit_pos;
> +
> +	raw_spin_lock_irqsave(&mn_pmu->lock, flags);
> +
> +	/* Read the INTS register */
> +	hisi_djtag_readreg(module_id, MN1_BANK_SELECT, MN1_INTS_REG_OFF,
> +							client, &value);

Weird alignment here. Please only align up to the '('.

> +	if (!value) {
> +		raw_spin_unlock_irqrestore(&mn_pmu->lock, flags);
> +		return IRQ_NONE;
> +	}
> +
> +	/* Find the counter index which overflowed and handle them */
> +	for (bit_pos = 0; bit_pos < HISI_MAX_CFG_MN_CNTR; bit_pos++) {
> +		if (test_bit(bit_pos, (void *)&value)) {

This casting is incorrect. Please listen to the compiler in future, and
don't bodge around it like this.

Make value an unsigned long, and use another temporary variable for the
hisi_djtag_readreg() call (i.e. don't cast to a u32 there either).

e.g.
	unsigned long overflown;
	u32 ints;
	int idx;

	hisi_djtag_readreg(module_id, MN1_BANK_SELECT, MN1_INTS_REG_OFF,
	                   client, &ints);
	
	...

	overflown = ints;

	for_each_set_bit(idx, &overflown, HISI_MAX_CFG_MN_CNTR) {

		...

	}


> +			/* Clear the IRQ status flag */
> +			hisi_djtag_writereg(module_id, MN1_BANK_SELECT,
> +				MN1_INTC_REG_OFF, (1 << bit_pos), client);
> +
> +			/* Get the corresponding event struct */
> +			event = mn_pmu->hw_perf_events[bit_pos];
> +			if (!event)
> +				continue;

Do we expect to take interrupts for an event which does not exist?

Elsewhere we do not, and we WARN_ON_ONCE() for this case.

[...]

> +static int hisi_mn_init_irq(int irq, struct hisi_pmu *mn_pmu,
> +				     struct hisi_djtag_client *client)
> +{
> +	struct hisi_mn_data *mn_data = mn_pmu->hwmod_data;
> +	u32 module_id = GET_MODULE_ID(mn_data);
> +	struct device *dev = &client->dev;
> +	int rc;
> +
> +	rc = devm_request_irq(dev, irq, hisi_pmu_mn_isr,
> +			       IRQF_NOBALANCING | IRQF_NO_THREAD,
> +					       dev_name(dev), mn_pmu);
> +	if (rc) {
> +		dev_err(dev, "Could not request IRQ:%d\n", irq);
> +		return rc;
> +	}
> +
> +	/* Overflow interrupt also should use the same CPU */
> +	rc = irq_set_affinity(irq, &mn_pmu->cpu);
> +	if (rc) {
> +		dev_err(dev, "could not set IRQ affinity!\n");
> +		return rc;
> +	}
> +
> +	/*
> +	 * Unmask all interrupts in Mask register
> +	 * Enable all IRQ's
> +	 */
> +	hisi_mn_enable_interrupts(module_id, client);

Nit: s/IRQ's/IRQs/

We've only requested one interrupt. Why are we manipulating others?

[...]

> +static int hisi_mn_init_irqs_fdt(struct device *dev,
> +				struct hisi_pmu *mn_pmu)
> +{
> +	struct hisi_mn_data *mn_data = mn_pmu->hwmod_data;
> +	struct hisi_djtag_client *client = mn_data->client;
> +	int irq = -1, num_irqs, i;
> +
> +	num_irqs = of_irq_count(dev->of_node);

Surely we expect a specific number of interrupts?

> +	for (i = 0; i < num_irqs; i++) {
> +		irq = of_irq_get(dev->of_node, i);
> +		if (irq < 0)
> +			dev_info(dev, "No IRQ resource!\n");
> +	}

Why are we throwing these away?

> +
> +	if (irq < 0)
> +		return 0;
> +
> +	/* The last entry in the IRQ list to be chosen
> +	 * This is as per mbigen-v2 IRQ mapping
> +	 */
> +	return hisi_mn_init_irq(irq, mn_pmu, client);

I don't understand this comment.

Why do we only use the list IRQ?

What does this have to do with the mbigen?

No ordering requirement was described in the DT binding.

Thanks,
Mark.