Re: [PATCH v10 04/27] clocksource: Add a new timer-ingenic driver

[Thierry Reding]

On Sat, Mar 02, 2019 at 08:33:50PM -0300, Paul Cercueil wrote:
[...]
> diff --git a/drivers/clocksource/ingenic-timer.c b/drivers/clocksource/ingenic-timer.c
[...]
> +struct ingenic_tcu {
> +	const struct ingenic_soc_info *soc_info;
> +	struct regmap *map;
> +	struct clk *clk, *timer_clk, *cs_clk;
> +
> +	struct irq_domain *domain;
> +	unsigned int nb_parent_irqs;
> +	u32 parent_irqs[3];
> +
> +	struct clk_hw_onecell_data *clocks;
> +
> +	unsigned int timer_channel, cs_channel;
> +	struct clock_event_device cevt;
> +	struct clocksource cs;
> +	char name[4];
> +
> +	unsigned long pwm_channels_mask;
> +};
> +
> +static struct ingenic_tcu *ingenic_tcu;

Is there really a need for this? Seems like the only two reasons for why
you keep this around are as pointed out below.

> +void __iomem *ingenic_tcu_base;
> +EXPORT_SYMBOL_GPL(ingenic_tcu_base);

Same here.

> +static u64 notrace ingenic_tcu_timer_read(void)
> +{
> +	unsigned int channel = ingenic_tcu->cs_channel;
> +	u16 count;
> +
> +	count = readw(ingenic_tcu_base + TCU_REG_TCNTc(channel));

Can't yo do this via the regmap?

> +
> +	return count;
> +}
> +
> +static u64 notrace ingenic_tcu_timer_cs_read(struct clocksource *cs)
> +{
> +	return ingenic_tcu_timer_read();
> +}

And here you've got access to the struct clocksource *, from which you
should be able to get at struct ingenic_tcu * using container_of.

[...]
> +static int __init ingenic_tcu_init(struct device_node *np)
> +{
> +	const struct of_device_id *id = of_match_node(ingenic_tcu_of_match, np);
> +	const struct ingenic_soc_info *soc_info = id->data;
> +	struct ingenic_tcu *tcu;
> +	struct resource res;
> +	void __iomem *base;
> +	long rate;
> +	int ret;
> +
> +	of_node_clear_flag(np, OF_POPULATED);
> +
> +	tcu = kzalloc(sizeof(*tcu), GFP_KERNEL);
> +	if (!tcu)
> +		return -ENOMEM;
> +
> +	/* Enable all TCU channels for PWM use by default except channel 0
> +	 * and channel 1.
> +	 */
> +	tcu->pwm_channels_mask = GENMASK(soc_info->num_channels - 1, 2);
> +	of_property_read_u32(np, "ingenic,pwm-channels-mask",
> +			     (u32 *)&tcu->pwm_channels_mask);
> +
> +	/* Verify that we have at least two free channels */
> +	if (hweight8(tcu->pwm_channels_mask) > soc_info->num_channels - 2) {
> +		pr_crit("ingenic-tcu: Invalid PWM channel mask: 0x%02lx\n",
> +			tcu->pwm_channels_mask);
> +		return -EINVAL;
> +	}
> +
> +	tcu->soc_info = soc_info;
> +	ingenic_tcu = tcu;
> +
> +	tcu->timer_channel = find_first_zero_bit(&tcu->pwm_channels_mask,
> +						 soc_info->num_channels);
> +	tcu->cs_channel = find_next_zero_bit(&tcu->pwm_channels_mask,
> +					     soc_info->num_channels,
> +					     tcu->timer_channel + 1);
> +
> +	base = of_io_request_and_map(np, 0, NULL);
> +	if (IS_ERR(base)) {
> +		ret = PTR_ERR(base);
> +		goto err_free_ingenic_tcu;
> +	}
> +
> +	of_address_to_resource(np, 0, &res);
> +
> +	ingenic_tcu_base = base;
> +
> +	tcu->map = regmap_init_mmio(NULL, base, &ingenic_tcu_regmap_config);
> +	if (IS_ERR(tcu->map)) {
> +		ret = PTR_ERR(tcu->map);
> +		goto err_iounmap;
> +	}
> +
> +	tcu->clk = of_clk_get_by_name(np, "tcu");
> +	if (IS_ERR(tcu->clk)) {
> +		ret = PTR_ERR(tcu->clk);
> +		pr_crit("ingenic-tcu: Unable to find TCU clock: %i\n", ret);
> +		goto err_free_regmap;
> +	}
> +
> +	ret = clk_prepare_enable(tcu->clk);
> +	if (ret) {
> +		pr_crit("ingenic-tcu: Unable to enable TCU clock: %i\n", ret);
> +		goto err_clk_put;
> +	}
> +
> +	ret = ingenic_tcu_intc_init(tcu, np);
> +	if (ret)
> +		goto err_clk_disable;
> +
> +	ret = ingenic_tcu_clk_init(tcu, np);
> +	if (ret)
> +		goto err_tcu_intc_cleanup;
> +
> +	ret = ingenic_tcu_clocksource_init(tcu);
> +	if (ret)
> +		goto err_tcu_clk_cleanup;
> +
> +	ret = ingenic_tcu_timer_init(tcu);
> +	if (ret)
> +		goto err_tcu_clocksource_cleanup;
> +
> +	// Register the sched_clock at the very end as there's no way to undo it
> +	rate = clk_get_rate(tcu->cs_clk);
> +	sched_clock_register(ingenic_tcu_timer_read, 16, rate);

Oh wow... so you managed to nicely encapsulate everything and now this
seems to be the only reason why you need to rely on global variables.

That's unfortunate. I suppose we could go and add a void *data parameter
to sched_clock_register() and pass that to the read() function. That way
you could make this completely independent of global variables, but
there are 73 callers of sched_clock_register() and they are spread all
over the place, so sounds a bit daunting to me.

> +
> +	return 0;
> +
> +err_tcu_clocksource_cleanup:
> +	ingenic_tcu_clocksource_cleanup(tcu);
> +err_tcu_clk_cleanup:
> +	ingenic_tcu_clk_cleanup(tcu, np);
> +err_tcu_intc_cleanup:
> +	ingenic_tcu_intc_cleanup(tcu);
> +err_clk_disable:
> +	clk_disable_unprepare(tcu->clk);
> +err_clk_put:
> +	clk_put(tcu->clk);
> +err_free_regmap:
> +	regmap_exit(tcu->map);
> +err_iounmap:
> +	iounmap(base);
> +	release_mem_region(res.start, resource_size(&res));
> +err_free_ingenic_tcu:
> +	kfree(tcu);
> +	return ret;
> +}
> +
> +TIMER_OF_DECLARE(jz4740_tcu_intc,  "ingenic,jz4740-tcu",  ingenic_tcu_init);
> +TIMER_OF_DECLARE(jz4725b_tcu_intc, "ingenic,jz4725b-tcu", ingenic_tcu_init);
> +TIMER_OF_DECLARE(jz4770_tcu_intc,  "ingenic,jz4770-tcu",  ingenic_tcu_init);
> +
> +
> +static int __init ingenic_tcu_probe(struct platform_device *pdev)
> +{
> +	platform_set_drvdata(pdev, ingenic_tcu);

Then there's also this. Oh well... nevermind then.

> +bool ingenic_tcu_pwm_can_use_chn(unsigned int channel)
> +{
> +	return !!(ingenic_tcu->pwm_channels_mask & BIT(channel));
> +}
> +EXPORT_SYMBOL_GPL(ingenic_tcu_pwm_can_use_chn);

I wonder if we could make this slightly nicer, though. Judging by the
name, this one seems like it would only ever be used by the PWM. If the
PWM is a child of the TCU, could it not pass in a struct device * that
points to its parent into this? Or perhaps pass its own struct device *
and have this function look up the struct ingenic_tcu from that? Should
be something trivial as:

	bool ingenic_tcu_pwm_can_use_channel(struct device *dev, unsigned int channel)
	{
		struct ingenic_tcu *tcu = dev_get_drvdata(dev->parent);

		return !!(tcu->pwm_channels_mask & BIT(channel));
	}

Thierry

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