linux-kernel - Re: [PATCH] gpio: langwell: convert to use irq

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Date:	Thu, 19 Apr 2012 12:39:20 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Cc:	linus.walleij@...ricsson.com
Subject: Re: [PATCH] gpio: langwell: convert to use irq_domain

On Tue, 10 Apr 2012 15:05:42 +0300, Mika Westerberg <mika.westerberg@...ux.intel.com> wrote:
> irq_domain already provides a facility to translate from hardware IRQ
> numbers to Linux IRQ numbers so use that instead of open-coding the logic
> in the driver.
> 
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
> This applies on top of my 3 previous patches for gpio-langwell.c. I wasn't
> sure about selecting IRQ_DOMAIN in the driver Kconfig but it seems not to
> cause any problems when I tested this on Medfield based platform.
> 
>  drivers/gpio/Kconfig         |    1 +
>  drivers/gpio/gpio-langwell.c |   21 +++++++++++++--------
>  2 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index edadbda..2e8849f 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -399,6 +399,7 @@ config GPIO_BT8XX
>  config GPIO_LANGWELL
>  	bool "Intel Langwell/Penwell GPIO support"
>  	depends on PCI && X86
> +	select IRQ_DOMAIN
>  	help
>  	  Say Y here to support Intel Langwell/Penwell GPIO.
>  
> diff --git a/drivers/gpio/gpio-langwell.c b/drivers/gpio/gpio-langwell.c
> index 52f00d3..028c7be 100644
> --- a/drivers/gpio/gpio-langwell.c
> +++ b/drivers/gpio/gpio-langwell.c
> @@ -36,6 +36,7 @@
>  #include <linux/gpio.h>
>  #include <linux/slab.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/irqdomain.h>
>  
>  /*
>   * Langwell chip has 64 pins and thus there are 2 32bit registers to control
> @@ -66,8 +67,8 @@ struct lnw_gpio {
>  	struct gpio_chip		chip;
>  	void				*reg_base;
>  	spinlock_t			lock;
> -	unsigned			irq_base;
>  	struct pci_dev			*pdev;
> +	struct irq_domain		*domain;
>  };
>  
>  static void __iomem *gpio_reg(struct gpio_chip *chip, unsigned offset,
> @@ -176,13 +177,13 @@ static int lnw_gpio_direction_output(struct gpio_chip *chip,
>  static int lnw_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
>  {
>  	struct lnw_gpio *lnw = container_of(chip, struct lnw_gpio, chip);
> -	return lnw->irq_base + offset;
> +	return irq_find_mapping(lnw->domain, offset);
>  }
>  
>  static int lnw_irq_type(struct irq_data *d, unsigned type)
>  {
>  	struct lnw_gpio *lnw = irq_data_get_irq_chip_data(d);
> -	u32 gpio = d->irq - lnw->irq_base;
> +	u32 gpio = d->hwirq;
>  	unsigned long flags;
>  	u32 value;
>  	void __iomem *grer = gpio_reg(&lnw->chip, gpio, GRER);
> @@ -256,7 +257,7 @@ static void lnw_irq_handler(unsigned irq, struct irq_desc *desc)
>  			pending &= ~mask;
>  			/* Clear before handling so we can't lose an edge */
>  			writel(mask, gedr);
> -			generic_handle_irq(lnw->irq_base + base + gpio);
> +			generic_handle_irq(gpio_to_irq(base + gpio));
>  		}
>  	}
>  
> @@ -369,7 +370,9 @@ static int __devinit lnw_gpio_probe(struct pci_dev *pdev,
>  		dev_err(&pdev->dev, "can't allocate IRQ descs\n");
>  		goto err3;
>  	}
> -	lnw->irq_base = retval;
> +	irq_base = retval;
> +	lnw->domain = irq_domain_add_legacy(NULL, ngpio, irq_base, 0,
> +					    &irq_domain_simple_ops, NULL);

Instead of manually allocating irq_descs and using the legacy domain,
the driver should instead use a linear mapping and then defer
allocating irq_descs to when an irq is actually requested.

The linear domain will happily handle allocating your irq_descs for
you.

>  
>  	lnw->reg_base = base;
>  	lnw->chip.label = dev_name(&pdev->dev);
> @@ -395,9 +398,11 @@ static int __devinit lnw_gpio_probe(struct pci_dev *pdev,
>  	irq_set_handler_data(pdev->irq, lnw);
>  	irq_set_chained_handler(pdev->irq, lnw_irq_handler);
>  	for (i = 0; i < lnw->chip.ngpio; i++) {
> -		irq_set_chip_and_handler_name(i + lnw->irq_base, &lnw_irqchip,
> +		unsigned int irq = irq_find_mapping(lnw->domain, i);
> +
> +		irq_set_chip_and_handler_name(irq, &lnw_irqchip,
>  					      handle_simple_irq, "demux");
> -		irq_set_chip_data(i + lnw->irq_base, lnw);
> +		irq_set_chip_data(irq, lnw);

Also, when you switch to the linear mapping, the body of this for loop
will need to be moved into the irq_domain .map callback.

g.
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