Re: [PATCH 2/2] clocksource/drivers/nxp-timer: Add the System Timer Module for the s32g platform

[Daniel Lezcano]

Hi Ghennadi,

thanks for the review


On 25/03/2025 08:28, Ghennadi Procopciuc wrote:

[ ... ]

> > +static int __init nxp_stm_clocksource_init(struct device *dev, const char *name,
> > +					   void __iomem *base, struct clk *clk)
> > +{
> > +	struct stm_timer *stm_timer;
> > +	int ret;
> > +
> > +	stm_timer = devm_kzalloc(dev, sizeof(*stm_timer), GFP_KERNEL);
> > +	if (!stm_timer)
> > +		return -ENOMEM;
> > +
> > +	stm_timer->base = base;
> > +	stm_timer->rate = clk_get_rate(clk);
> > +
> > +	stm_timer->scs.cs.name = name;
> > +	stm_timer->scs.cs.rating = 460;
> > +	stm_timer->scs.cs.read = nxp_stm_clocksource_read;
> > +	stm_timer->scs.cs.enable = nxp_stm_clocksource_enable;
> > +	stm_timer->scs.cs.disable = nxp_stm_clocksource_disable;
> > +	stm_timer->scs.cs.suspend = nxp_stm_clocksource_suspend;
> > +	stm_timer->scs.cs.resume = nxp_stm_clocksource_resume;
> > +	stm_timer->scs.cs.mask = CLOCKSOURCE_MASK(32);
> > +	stm_timer->scs.cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;
> > +
> > +	ret = clocksource_register_hz(&stm_timer->scs.cs, stm_timer->rate);
> > +	if (ret)
> > +		return ret;
>
> clocksource_unregister during remove callback for cleanup?

Sorry I don't get it :/

There is no cleanup after the clocksource_register_hz() is successful

> > +
> > +	stm_sched_clock = stm_timer;
> > +
> > +	sched_clock_register(nxp_stm_read_sched_clock, 32, stm_timer->rate);
> > +
> > +	dev_set_drvdata(dev, stm_timer);
>
> Is this used?

Nope, I'll remove it.

> > +
> > +	dev_dbg(dev, "Registered clocksource %s\n", name);
> > +
> > +	return 0;
> > +}

[ ... ]

> > +static int nxp_stm_clockevent_set_next_event(unsigned long delta, struct clock_event_device *ced)
> > +{
> > +	struct stm_timer *stm_timer = ced_to_stm(ced);
> > +	u32 val;
> > +
> > +	nxp_stm_clockevent_disable(stm_timer);
>
> While examining the code base, I came across the
> drivers/clocksource/timer-imx-gpt.c file, specifically the
> mx1_2_set_next_event function, which includes a protection against
> missing events. Using a similar approach would allow us to keep the STM
> module enabled while only altering the channel's register state. This
> risk can also be mitigated by adjusting min_delta_ns based on tick
> frequency.

How would you validate that ?


> > +	stm_timer->sce.delta = delta;
> > +
> > +	val = nxp_stm_clockevent_read_counter(stm_timer) + delta;
> > +
> > +	writel(val, stm_timer->base + STM_CHANNEL(0) + STM_CMP);
> > +
> > +	nxp_stm_clockevent_enable(stm_timer);
> > +
> > +	return 0;
> > +}
> > +
> > +static int nxp_stm_clockevent_set_periodic(struct clock_event_device *ced)
> > +{
> > +	struct stm_timer *stm_timer = ced_to_stm(ced);
> > +
> > +        return nxp_stm_clockevent_set_next_event(stm_timer->rate, ced);
> > +}
> > +
> > +static int __init nxp_stm_clockevent_broadcast_init(struct device *dev, const char *name, void __iomem *base,
> > +						    int irq, struct clk *clk)
> > +{
> > +	struct stm_timer *stm_timer;
> > +	int ret;
> > +
> > +	stm_timer = devm_kzalloc(dev, sizeof(*stm_timer), GFP_KERNEL);
> > +	if (!stm_timer)
> > +		return -ENOMEM;
> > +
> > +	stm_timer->base = base;
> > +	stm_timer->rate = clk_get_rate(clk);
> > +
> > +	stm_timer->sce.ced.name = name;
> > +	stm_timer->sce.ced.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
> > +	stm_timer->sce.ced.set_state_shutdown = nxp_stm_clockevent_shutdown;
> > +	stm_timer->sce.ced.set_state_periodic = nxp_stm_clockevent_set_periodic;
> > +	stm_timer->sce.ced.set_next_event = nxp_stm_clockevent_set_next_event;
> > +	stm_timer->sce.ced.cpumask = cpu_possible_mask;
> > +	stm_timer->sce.ced.rating = 460;
> > +	stm_timer->sce.ced.irq = irq;
> > +
> > +	nxp_stm_clockevent_irq_clr(stm_timer);
> > +
> > +	ret = request_irq(irq, nxp_stm_clockevent_interrupt,
> > +			  IRQF_TIMER | IRQF_NOBALANCING, name, &stm_timer->sce.ced);
> > +	if (ret) {
> > +		dev_err(dev, "Unable to allocate interrupt line: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	clockevents_config_and_register(&stm_timer->sce.ced, stm_timer->rate, 1, 0xffffffff);
> > +
> > +	dev_dbg(dev, "Registered broadcast clockevent %s irq=%d\n", name, irq);
> > +
> > +	return 0;
> > +}
> > +
> > +static int __init nxp_stm_clockevent_per_cpu_init(struct device *dev, const char *name, void __iomem *base,
> > +						  int irq, struct clk *clk, int cpu)
> > +{
>
> This function duplicates a significant portion of the previous one. To
> avoid code duplication, it would be beneficial to extract the common
> part into a dedicated function.

Sure

> > +	struct stm_timer *stm_timer;
> > +	int ret;
> > +
> > +	stm_timer = devm_kzalloc(dev, sizeof(*stm_timer), GFP_KERNEL);
> > +	if (!stm_timer)
> > +		return -ENOMEM;
> > +
> > +	stm_timer->base = base;
> > +	stm_timer->rate = clk_get_rate(clk);
> > +
> > +	stm_timer->sce.ced.name = name;
> > +	stm_timer->sce.ced.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
> > +	stm_timer->sce.ced.set_state_shutdown = nxp_stm_clockevent_shutdown;
> > +	stm_timer->sce.ced.set_state_periodic = nxp_stm_clockevent_set_periodic;
> > +	stm_timer->sce.ced.set_next_event = nxp_stm_clockevent_set_next_event;
> > +	stm_timer->sce.ced.cpumask = cpumask_of(cpu);
> > +	stm_timer->sce.ced.rating = 460;
> > +	stm_timer->sce.ced.irq = irq;
> > +
> > +	nxp_stm_clockevent_irq_clr(stm_timer);
> > +
> > +	ret = request_irq(irq, nxp_stm_clockevent_interrupt,
> > +			  IRQF_TIMER | IRQF_NOBALANCING, name, &stm_timer->sce.ced);
>
> devm_request_irq instead ?

Yes

> > +	if (ret) {
> > +		dev_err(dev, "Unable to allocate interrupt line: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	per_cpu(stm_timers, cpu) = stm_timer;
> > +
> > +	dev_dbg(dev, "Initialized per cpu clockevent name=%s, irq=%d, cpu=%d\n", name, irq, cpu);
> > +
> > +	return 0;
> > +}
> > +
> > +static int nxp_stm_clockevent_starting_cpu(unsigned int cpu)
> > +{
> > +	struct stm_timer *stm_timer = per_cpu(stm_timers, cpu);
> > +	int ret;
> > +
> > +	if (WARN_ON(!stm_timer))
> > +		return -EFAULT;
> > +
> > +	ret = irq_force_affinity(stm_timer->sce.ced.irq, cpumask_of(cpu));
> > +	if (ret)
> > +		return ret;
> > +
> > +	clockevents_config_and_register(&stm_timer->sce.ced, stm_timer->rate, 1, 0xffffffff);
> > +
> > +	return 0;
> > +}
> > +
> > +static int __init nxp_stm_timer_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct device_node *np = dev->of_node;
> > +	struct stm_instances *stm_instances;
> > +	const char *name = of_node_full_name(np);
> > +	void __iomem *base;
> > +	int irq, ret;
> > +	struct clk *clk;
> > +
> > +	stm_instances = (typeof(stm_instances))of_device_get_match_data(dev);
> > +	if (!stm_instances) {
> > +		dev_err(dev, "No STM instances associated with a cpu");
> > +		return -EINVAL;
> > +	}
> > +
> > +	base = devm_of_iomap(dev, np, 0, NULL);
> > +	if (IS_ERR(base)) {
> > +		dev_err(dev, "Failed to iomap %pOFn\n", np);
> > +		return PTR_ERR(base);
> > +	}
> > +
> > +	irq = irq_of_parse_and_map(np, 0);
> > +	if (irq <= 0) {
> > +		dev_err(dev, "Failed to parse and map IRQ: %d\n", irq);
> > +		return -EINVAL;
> > +	}
>
>  From commit description:
>
> > The first probed STM is used as a clocksource, the second will be the
> > broadcast timer and the rest are used as a clockevent with the
> > affinity set to a CPU.
>
> Why is the interrupt mandatory when the node is probed as a clocksource?

It relies on the DT description and it does not hurt to have a 
consistent code path for clockevent / clocksource even if the interrupt 
is not requested for the clocksource later.

> > +
> > +	clk = devm_clk_get(dev, NULL);
> > +	if (IS_ERR(clk)) {
> > +		dev_err(dev, "Clock not found\n");
>
> Missing irq_dispose_mapping ?

Yeah ...

> > +		return PTR_ERR(clk);
> > +	}
> > +
> > +	ret = clk_prepare_enable(clk);
> > +	if (ret) {
> > +		dev_err(dev, "Failed to enable STM timer clock: %d\n", ret);
> > +		return ret;
> > +	}
>
> devm_clk_get_enabled instead of devm_clk_get + clk_prepare_enable ?

Yes, good point

> > +
> > +	if (!stm_instances->clocksource && (stm_instances->features & STM_CLKSRC)) {
> > +
> > +		/*
> > +		 * First probed STM will be a clocksource
> > +		 */
> > +		ret = nxp_stm_clocksource_init(dev, name, base, clk);
> > +		if (ret)
> > +			return ret;
> > +		stm_instances->clocksource++;
> > +
> > +	} else if (!stm_instances->clockevent_broadcast &&
> > +		   (stm_instances->features & STM_CLKEVT_BROADCAST)) {
> > +
> > +		/*
> > +		 * Second probed STM will be a broadcast clockevent
> > +		 */
> > +		ret = nxp_stm_clockevent_broadcast_init(dev, name, base, irq, clk);
> > +		if (ret)
> > +			return ret;
> > +		stm_instances->clockevent_broadcast++;
> > +
> > +	} else if (stm_instances->clockevent_per_cpu < num_possible_cpus() &&
> > +		   (stm_instances->features & STM_CLKEVT_PER_CPU)) {
> > +
> > +		/*
> > +		 * Next probed STM will be a per CPU clockevent, until
> > +		 * we probe as much as we have CPUs available on the
> > +		 * system, we do a partial initialization
> > +		 */
> > +		ret = nxp_stm_clockevent_per_cpu_init(dev, name, base, irq, clk,
> > +						      stm_instances->clockevent_per_cpu);
> > +		if (ret)
> > +			return ret;
> > +
> > +		stm_instances->clockevent_per_cpu++;
> > +
> > +		/*
> > +		 * The number of probed STM for per CPU clockevent is
> > +		 * equal to the number of available CPUs on the
> > +		 * system. We install the cpu hotplug to finish the
> > +		 * initialization by registering the clockevents
> > +		 */
> > +		if (stm_instances->clockevent_per_cpu == num_possible_cpus()) {
> > +			ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "STM timer:starting",
> > +						nxp_stm_clockevent_starting_cpu, NULL);
> > +			if (ret < 0)
> > +				return ret;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static struct stm_instances s32g_stm_instances = { .features = STM_CLKSRC | STM_CLKEVT_PER_CPU };
> > +
> > +static const struct of_device_id nxp_stm_of_match[] = {
> > +	{ .compatible = "nxp,s32g2-stm", &s32g_stm_instances },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(of, nxp_stm_of_match);
> > +
> > +static struct platform_driver nxp_stm_probe = {
> > +	.probe	= nxp_stm_timer_probe,
> > +	.driver	= {
> > +		.name = "nxp-stm",
> > +		.of_match_table = of_match_ptr(nxp_stm_of_match),
> > +	},
> > +};
> > +module_platform_driver(nxp_stm_probe);
> > +
> > +MODULE_DESCRIPTION("NXP System Timer Module driver");
> > +MODULE_LICENSE("GPL");


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