linux-kernel - Re: [PATCH V7 1/1] drivers/gpio: Altera soft IP GPIO driver and devicetree binding

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Date:	Tue, 15 Apr 2014 18:00:39 +0800
From:	Tien Hock Loh <thloh@...era.com>
To:	Tien Hock Loh <thloh@...era.com>
Cc:	Josh Cartwright <joshc@...eaurora.org>, robh+dt@...nel.org,
	pawel.moll@....com, Mark Rutland <mark.rutland@....com>,
	ijc+devicetree@...lion.org.uk, Kumar Gala <galak@...eaurora.org>,
	Rob Landley <rob@...dley.net>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	dinguyen@...era.com, "lftan@...era.com" <lftan@...era.com>
Subject: Re: [PATCH V7 1/1] drivers/gpio: Altera soft IP GPIO driver and
 devicetree binding

>>>>> Add driver support for Altera GPIO soft IP, including interrupts and I/O.
>>>>> Tested on Altera CV SoC board using dipsw and LED using LED framework.
>>>>>
>>>>> Signed-off-by: Tien Hock Loh <thloh@...era.com>
>>>>> ---
>>>>
>>>>> +             return -ENOMEM;
>>>>> +     }
>>>>> +     altera_gc->domain = 0;
>>>>> +
>>>>> +     spin_lock_init(&altera_gc->gpio_lock);
>>>>> +
>>>>> +     id = pdev->id;
>>>>> +
>>>>> +     if (of_property_read_u32(node, "altr,gpio-bank-width", &reg))
>>>>> +             /*By default assume full GPIO controller*/
>>>>> +             altera_gc->mmchip.gc.ngpio = 32;
>>>>> +     else
>>>>> +             altera_gc->mmchip.gc.ngpio = reg;
>>>>> +
>>>>> +     if (altera_gc->mmchip.gc.ngpio > 32) {
>>>>> +             dev_warn(&pdev->dev,
>>>>> +                     "ngpio is greater than 32, defaulting to 32\n");
>>>>> +             altera_gc->mmchip.gc.ngpio = 32;
>>>>> +     }
>>>>> +
>>>>> +     altera_gc->mmchip.gc.direction_input    = altera_gpio_direction_input;
>>>>> +     altera_gc->mmchip.gc.direction_output   = altera_gpio_direction_output;
>>>>> +     altera_gc->mmchip.gc.get                = altera_gpio_get;
>>>>> +     altera_gc->mmchip.gc.set                = altera_gpio_set;
>>>>> +     altera_gc->mmchip.gc.to_irq             = altera_gpio_to_irq;
>>>>> +     altera_gc->mmchip.gc.owner              = THIS_MODULE;
>>>>> +
>>>>> +     ret = of_mm_gpiochip_add(node, &altera_gc->mmchip);
>>>>> +     if (ret) {
>>>>> +             dev_err(&pdev->dev, "Failed adding memory mapped gpiochip\n");
>>>>> +             return ret;
>>>>> +     }
>>>>> +
>>>>> +     platform_set_drvdata(pdev, altera_gc);
>>>>> +
>>>>> +     altera_gc->mapped_irq = irq_of_parse_and_map(node, 0);
>>>>>
>>>>
>>>> platform_get_irq(pdev, 0);
>>>>
>>> OK.
>>>
>>
>> platform_get_irq doesn't create the irq mapping which is needed by the
>> driver. Since this driver is targeted at using of, should I be using
>> irq_of_parse_and_map or should I still redo the codes with
>> platform_get_irq and irq_create_mapping? I think the latter would be
>> introducing code redundancy. Please advice.
>
> Yes, it is technically true that platform_get_irq() doesn't do the mapping directly, but that's
> because the mapping is setup earlier, when
> of_device_alloc() (drivers/of/platform.c) allocates resources for your platform device.
>
> Calling irq_of_parse_and_map() should be unnecessary.

I checked and tried running the without irq_create_mapping but it
seems the mapping is not done.
What I've seen other GPIO driver is doing is to create the mapping
during the gpio_to_irq call. However Linus suggested we are avoiding
that route, thus the use of irq_of_parse_and_map. Do you agree with my
findings?

>>
>> Thanks.
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