linux-kernel - Re: [PATCH v6 2/2] counter: add IRQ or GPIO based event counter

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Date:   Sun, 21 Feb 2021 15:41:32 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Rob Herring <robh+dt@...nel.org>,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        Ahmad Fatoum <a.fatoum@...gutronix.de>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        David Jander <david@...tonic.nl>,
        Robin van der Gracht <robin@...tonic.nl>,
        linux-iio@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v6 2/2] counter: add IRQ or GPIO based event counter

On Tue, 16 Feb 2021 09:13:56 +0100
Oleksij Rempel <o.rempel@...gutronix.de> wrote:

> Add simple IRQ or GPIO base event counter. This device is used to measure
> rotation speed of some agricultural devices, so no high frequency on the
> counter pin is expected.
> 
> The maximal measurement frequency depends on the CPU and system load. On
> the idle iMX6S I was able to measure up to 20kHz without count drops.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> Reviewed-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
A FYI note inline.

Driver looks good to me.

Jonathan

> ---
>  MAINTAINERS                     |   7 +
>  drivers/counter/Kconfig         |  10 ++
>  drivers/counter/Makefile        |   1 +
>  drivers/counter/interrupt-cnt.c | 249 ++++++++++++++++++++++++++++++++
>  4 files changed, 267 insertions(+)
>  create mode 100644 drivers/counter/interrupt-cnt.c
> 
...

> +static int interrupt_cnt_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct interrupt_cnt_priv *priv;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->irq = platform_get_irq_optional(pdev,  0);
> +	if (priv->irq == -ENXIO)
> +		priv->irq = 0;
> +	else if (priv->irq < 0)
> +		return dev_err_probe(dev, priv->irq, "failed to get IRQ\n");
> +
> +	priv->gpio = devm_gpiod_get_optional(dev, NULL, GPIOD_IN);
> +	if (IS_ERR(priv->gpio))
> +		return dev_err_probe(dev, PTR_ERR(priv->gpio), "failed to get GPIO\n");
> +
> +	if (!priv->irq && !priv->gpio) {
> +		dev_err(dev, "IRQ and GPIO are not found. At least one source should be provided\n");
> +		return -ENODEV;
> +	}
> +
> +	if (!priv->irq) {
> +		int irq = gpiod_to_irq(priv->gpio);
> +
> +		if (irq < 0)
> +			return dev_err_probe(dev, irq, "failed to get IRQ from GPIO\n");
> +
> +		priv->irq = irq;
> +	}
> +
> +	priv->counter.priv = priv;
> +	priv->counter.name = dev_name(dev);
> +	priv->counter.parent = dev;
> +	priv->counter.ops = &interrupt_cnt_ops;
> +	priv->counter.counts = interrupt_cnts;
> +	priv->counter.num_counts = ARRAY_SIZE(interrupt_cnts);
> +	priv->counter.signals = interrupt_cnt_signals;
> +	priv->counter.num_signals = priv->gpio ?
> +				    ARRAY_SIZE(interrupt_cnt_signals) : 0;
> +
> +	irq_set_status_flags(priv->irq, IRQ_NOAUTOEN);

Just as a side note, there is a series that cleans up this case, though no
idea if it will make the merge window or not.

https://lore.kernel.org/linux-input/aefbe49321b845c98e505518314a93cc@hisilicon.com/

If it does we can tidy this up then.

> +	ret = devm_request_irq(dev, priv->irq, interrupt_cnt_isr,
> +			       IRQF_TRIGGER_RISING | IRQF_NO_THREAD,
> +			       INTERRUPT_CNT_NAME, priv);
> +	if (ret)
> +		return ret;
> +
> +	return devm_counter_register(dev, &priv->counter);
> +}
> +
...