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

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Date:	Thu, 14 Nov 2013 10:33:22 +0900
From:	Kyungmin Park <kmpark@...radead.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	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>
Subject: Re: [PATCH 1/4] mfd: max14577: Add max14577 MFD driver core

On Wed, Nov 13, 2013 at 10:13 PM, Mark Brown <broonie@...nel.org> wrote:
> 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.

It's not work with level triggering. as wm8994, it requires edge
triggering. previous time I send RFC patch to handle edge triggering
at regmap.

>
>> +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?

there's ordering issue, it should provide regulator which is used
others before USB probe. if not, it failed to use USB.
Other PMICs use also subsys_initcall for this reason.

Thank you,
Kyungmin Park
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