linux-kernel - Re: [PATCH 1/4] mfd: max14577: Add max14577 MFD driver core

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Date:	Wed, 13 Nov 2013 13:13:28 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Anton Vorontsov <anton@...msg.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>
Subject: Re: [PATCH 1/4] mfd: max14577: Add max14577 MFD driver core

On Wed, Nov 13, 2013 at 08:40:54AM +0100, Krzysztof Kozlowski wrote:

> +/**
> + * After resuming from suspend it may happen that IRQ is signalled but
> + * IRQ GPIO is not high. Also the interrupt registers won't have any data
> + * (all of them equal to 0x00).
> + *
> + * In such case retry few times reading the interrupt registers.
> + */
> +#define IRQ_READ_REG_RETRY_CNT		5

What is the cause here?  This smells like an unreliable workaround for
some other behaviour.  In general this all looks very like standard
regmap code.

> +	for (i = 0; i < MAX14577_IRQ_REGS_NUM; i++) {
> +		u8 mask_reg = max14577_mask_reg[i];
> +
> +		if (mask_reg == MAX14577_REG_INVALID ||
> +				IS_ERR_OR_NULL(max14577->regmap))
> +			continue;

Why would this code even be running if you don't have a register map?

> +		dev_info(max14577->dev, "Got interrupts [1:0x%02x, 2:0x%02x, 3:0x%02x]\n",
> +			irq_reg[MAX14577_IRQ_INT1], irq_reg[MAX14577_IRQ_INT2],
> +			irq_reg[MAX14577_IRQ_INT3]);

This is far too noisy, dev_dbg() at most.

> +		gpio_val = gpio_get_value(pdata->irq_gpio);
> +
> +		if (gpio_get_value(pdata->irq_gpio) == 0)
> +			dev_warn(max14577->dev, "IRQ GPIO is not high, retry reading interrupt registers\n");
> +	} while (gpio_val == 0 && --retry > 0);

This looks very strange...

> +	max14577->irq = gpio_to_irq(pdata->irq_gpio);
> +	ret = gpio_request(pdata->irq_gpio, "max14577_irq");
> +	if (ret) {
> +		dev_err(max14577->dev, "Failed requesting GPIO %d: %d\n",
> +				pdata->irq_gpio, ret);
> +		goto err;
> +	}
> +	gpio_direction_input(pdata->irq_gpio);
> +	gpio_free(pdata->irq_gpio);

This means the GPIO handling code that was present in the handling is
broken, it's trying to use the GPIO after it was freed.

> +	ret = request_threaded_irq(max14577->irq, NULL, max14577_irq_thread,
> +				   IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
> +				   "max14577-irq", max14577);

Are you *positive* this is a falling triggered IRQ?  All the code to do
with spinning reading the GPIO state during handling makes it look like
this is in fact an active low interrupt and a lot of the code in here is
working around trying to handle that as the wrong kind of IRQ.

> +int max14577_bulk_write(struct regmap *map, u8 reg, u8 *buf, int count)
> +{
> +	return regmap_bulk_write(map, reg, buf, count);
> +}
> +EXPORT_SYMBOL_GPL(max14577_bulk_write);

Given that these are basically all trivial wrappers around regmap they
probably ought to be static inlines in the header.

> +static struct max14577_platform_data *max14577_i2c_parse_dt(struct device *dev)
> +{

There's no DT binding document?

> +const struct dev_pm_ops max14577_pm = {
> +	.suspend = max14577_suspend,
> +	.resume = max14577_resume,
> +};

SET_SYSTEM_SLEEP_PM_OPS().

> +static int __init max14577_i2c_init(void)
> +{
> +	return i2c_add_driver(&max14577_i2c_driver);
> +}
> +subsys_initcall(max14577_i2c_init);

Why not module_i2c_driver?

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