linux-kernel - Re: [PATCH v4] gpio: Add support for Intel SoC PMIC (Crystal Cove)

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Date:	Tue, 27 May 2014 15:04:09 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
CC:	Alexandre Courbot <gnurou@...il.com>,
	"Zhu, Lejun" <lejun.zhu@...ux.intel.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	<jacob.jun.pan@...ux.intel.com>, <bin.yang@...el.com>
Subject: Re: [PATCH v4] gpio: Add support for Intel SoC PMIC (Crystal Cove)

Hi Mika,

On 05/27/2014 11:46 AM, Mika Westerberg wrote:
> On Tue, May 27, 2014 at 12:24:56PM +0300, Grygorii Strashko wrote:
>>>> +
>>>> +       if (retval) {
>>>> +               dev_warn(&pdev->dev, "request irq failed: %d\n", retval);
>>>> +               goto out;
>>>> +       }
>>>> +
>>>> +       retval = gpiochip_add(&cg->chip);
>>>> +       if (retval) {
>>>> +               dev_warn(&pdev->dev, "add gpio chip error: %d\n", retval);
>>>> +               goto out_free_irq;
>>>> +       }
>>
>> As to my mind, It'll be better to setup IRQ as last probing step and
>> free it as the first step of driver removing.
> 
> When gpiochip_add() is called the chip is exported to outside world. At
> that point anyone can start requesting GPIOs and setup GPIO based
> interrupts. How does that work if you setup the IRQ after you call
> gpiochip_add()?
> 

It's difficult for me to imagine case when GPIO will be accessed
until GPIO driver's probe is finished.

Regarding remove()/suspend() routines, It's like an axiom for me:
- always disable irq
- always stop all works/threads created by driver
- do everything else
(It's proved by dozens hours of debugging).

Anyway, above is just my opinion :)
So, It's up to you, because it's your code :)

Also FYI, I did fast analysis of GPIO drivers - funny statistic below:
- 16 drivers setup IRQs BEFORE calling gpiochip_add();
- 22 drivers setup IRQs AFTER calling gpiochip_add();

Best regards,
-grygorii
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