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

[Krzysztof Kozlowski]

On 24/03/2025 11:00, Daniel Lezcano 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;

You are aware that all node names will have exactly the same name? All
of them will be called "timer"?


> +	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;
> +
> +	stm_sched_clock = stm_timer;
> +
> +	sched_clock_register(nxp_stm_read_sched_clock, 32, stm_timer->rate);
> +
> +	dev_set_drvdata(dev, stm_timer);
> +
> +	dev_dbg(dev, "Registered clocksource %s\n", name);

Since all names will be the same, this makes little sense in debugging.
I guess you wanted one of the OF printk-formats for full node name.


> +
> +	return 0;
> +}
> +
> +static int nxp_stm_clockevent_read_counter(struct stm_timer *stm_timer)
> +{
> +	return readl(stm_timer->base + STM_CNT);
> +}
> +

...

> +
> +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);

No, you *cannot* drop the const. It's there on purpose. Match data
should be const because it defines per variant differences. That's why
the prototype of of_device_get_match_data() has such return type.
You just want some global singleton, not match data.

> +	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);

You need to clean up the downstream code to match upstream. All of these
should be return dev_err_probe().

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

And this is clearly incorrect - spamming logs. Syntax is:
return dev_err_probe

> +		return PTR_ERR(clk);
> +	}
> +
> +	ret = clk_prepare_enable(clk);

Drop, devm_clk_get_enabled.

> +	if (ret) {
> +		dev_err(dev, "Failed to enable STM timer clock: %d\n", ret);
> +		return ret;
> +	}
> +
> +	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++;

That's racy. Devices can be brought async, ideally. This should be
rather idr or probably entire structure protected with a mutex.

> +
> +	} 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 };

Missing const. Or misplaced - all file-scope static variables are
declared at the top.

> +
> +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),

Drop of_match_ptr, you have here warnings.

> +	},
> +};
> +module_platform_driver(nxp_stm_probe);
> +
> +MODULE_DESCRIPTION("NXP System Timer Module driver");
> +MODULE_LICENSE("GPL");


Best regards,
Krzysztof