Re: [PATCH v4] gpio: driver for PrimeCell PL061 GPIO controller

[Baruch Siach <baruch@tkos.co.il>]

Hi Andrew,

On Tue, Jun 09, 2009 at 02:02:39PM -0700, Andrew Morton wrote:
> On Sun,  7 Jun 2009 21:38:55 +0300
> Baruch Siach <baruch@tkos.co.il> wrote:
> 
> > This is a driver for the ARM PrimeCell PL061 GPIO AMBA peripheral. The driver
> > is implemented using the gpiolib framework.
> > 
> > This driver also includes support for the use of the PL061 as an interrupt
> > controller (secondary).
> > 
> > Signed-off-by: Baruch Siach <baruch@tkos.co.il>
> > ---
> > Changes in v4:
> > 	- Depend on CONFIG_ARM_AMBA
> > 	- Do not request the gpio for IRQ automatically, just warn if it's not 
> > 	  requested
> > 	- Remove SZ_4K
> > 	- Iterate through a linked list find the source of interrupt when 
> > 	  multiple PL061s are connected to the same IRQ trigger
> > 	- Move hardware register defines into the .c file
> 
> I generated an incremental diff so that we can see what you did.
> 
> 
> >  drivers/gpio/Kconfig       |    1 
> >  drivers/gpio/pl061.c       |   92 ++++++++++++++++-------------------
> >  include/linux/amba/pl061.h |   19 +++----
> >  3 files changed, 54 insertions(+), 58 deletions(-)
> > 
> > diff -puN drivers/gpio/Kconfig~gpio-driver-for-primecell-pl061-gpio-controller-v4 drivers/gpio/Kconfig
> > --- a/drivers/gpio/Kconfig~gpio-driver-for-primecell-pl061-gpio-controller-v4
> > +++ a/drivers/gpio/Kconfig
> > @@ -69,6 +69,7 @@ comment "Memory mapped GPIO expanders:"
> >  
> >  config GPIO_PL061
> >  	bool "PrimeCell PL061 GPIO support"
> > +	depends on ARM_AMBA
> >  	help
> >  	  Say yes here to support the PrimeCell PL061 GPIO device
> >  
> > diff -puN drivers/gpio/pl061.c~gpio-driver-for-primecell-pl061-gpio-controller-v4 drivers/gpio/pl061.c
> > --- a/drivers/gpio/pl061.c~gpio-driver-for-primecell-pl061-gpio-controller-v4
> > +++ a/drivers/gpio/pl061.c
> > @@ -14,6 +14,7 @@
> >  #include <linux/spinlock.h>
> >  #include <linux/errno.h>
> >  #include <linux/module.h>
> > +#include <linux/list.h>
> >  #include <linux/io.h>
> >  #include <linux/ioport.h>
> >  #include <linux/irq.h>
> > @@ -24,9 +25,22 @@
> >  #include <linux/amba/bus.h>
> >  #include <linux/amba/pl061.h>
> >  
> > +#define GPIODIR 0x400
> > +#define GPIOIS  0x404
> > +#define GPIOIBE 0x408
> > +#define GPIOIEV 0x40C
> > +#define GPIOIE  0x410
> > +#define GPIORIS 0x414
> > +#define GPIOMIS 0x418
> > +#define GPIOIC  0x41C
> > +
> >  #define PL061_GPIO_NR	8
> >  
> > +#define PL061_REG_SIZE	(4*1024)
> > +
> >  struct pl061_gpio {
> > +	struct list_head	list;
> 
> Some commentary which describes this field would be nice.  What lock
> protects it, what other list_head this list is anchored to, etc

I'll add a comment.

Regarding the lock, the only list_add() is done in the probe method, and this 
method is serialized, as far as I know.

> >  	/* Each of the two spinlocks protects a different set of hardware
> >  	 * regiters and data structurs. This decouples the code of the IRQ from
> >  	 * the GPIO code. This also makes the case of a GPIO routine call from
> > @@ -37,12 +51,8 @@ struct pl061_gpio {
> >  
> >  	void __iomem		*base;
> >  	struct gpio_chip	gc;
> > -	struct work_struct	gpio_free_work;
> > -	DECLARE_BITMAP(gpios_to_free, PL061_GPIO_NR);
> >  };
> >  
> > -static u32 (*pl061_pending_irq)(int irq);
> > -
> >  static int pl061_direction_input(struct gpio_chip *gc, unsigned offset)
> >  {
> >  	struct pl061_gpio *chip = container_of(gc, struct pl061_gpio, gc);
> > @@ -112,16 +122,6 @@ static void pl061_irq_disable(unsigned i
> >  	spin_unlock_irqrestore(&chip->irq_lock, flags);
> >  }
> >  
> > -static void pl061_irq_shutdown(unsigned irq)
> > -{
> > -	struct pl061_gpio *chip = get_irq_chip_data(irq);
> > -	int offset = irq_to_gpio(irq) - chip->gc.base;
> > -
> > -	pl061_irq_disable(irq);
> > -	set_bit(offset, chip->gpios_to_free);
> > -	schedule_work(&chip->gpio_free_work);
> > -}
> > -
> >  static void pl061_irq_enable(unsigned irq)
> >  {
> >  	struct pl061_gpio *chip = get_irq_chip_data(irq);
> > @@ -138,16 +138,10 @@ static void pl061_irq_enable(unsigned ir
> >  
> >  static unsigned int pl061_irq_startup(unsigned irq)
> >  {
> > -	int ret;
> > -
> > -	ret = gpio_request(irq_to_gpio(irq), "IRQ");
> > -	if (ret < 0) {
> > -		pr_warning("%s: warning: gpio_request(%d) returned %d\n",
> > -				__func__, irq_to_gpio(irq), ret);
> > -		return 0;
> > -	}
> > +	if (gpio_request(irq_to_gpio(irq), "IRQ") == 0)
> > +		pr_warning("%s: warning: GPIO%d has not been requested\n",
> > +				__func__, irq_to_gpio(irq));
> 
> This is wrong, isn't it?  gpio_request() returns 0 on success.

Russell said that gpio configuration is the responsibility of the platform 
code. Here I just warn when the gpio has not been requested, and thus 
gpio_request() succeeds. I'll add a comment.

> > -	gpio_direction_input(irq_to_gpio(irq));
> >  	pl061_irq_enable(irq);
> >  
> >  	return 0;
> > @@ -202,45 +196,38 @@ static struct irq_chip pl061_irqchip = {
> >  	.startup	= pl061_irq_startup,
> >  	.enable		= pl061_irq_enable,
> >  	.disable	= pl061_irq_disable,
> > -	.shutdown	= pl061_irq_shutdown,
> >  	.set_type	= pl061_irq_type,
> >  };
> >  
> >  static void pl061_irq_handler(unsigned irq, struct irq_desc *desc)
> >  {
> > +	struct list_head *chip_list = get_irq_chip_data(irq);
> > +	struct list_head *ptr;
> > +	struct pl061_gpio *chip;
> > +
> >  	desc->chip->ack(irq);
> > -	while (1) {
> > +	list_for_each(ptr, chip_list) {
> 
> What locking protects the newly-added list?

Do we need locking even though we list_add() only at probe time? (Compiling as 
a module is not supported, so this only happens at boot time).

> >  		unsigned long pending;
> >  		int gpio;
> >  
> > -		pending = pl061_pending_irq(irq);
> > +		chip = list_entry(ptr, struct pl061_gpio, list);
> > +		pending = readb(chip->base + GPIOMIS);
> > +		writeb(pending, chip->base + GPIOIC);
> > +
> >  		if (pending == 0)
> > -			break;
> > +			continue;
> >  
> > -		for_each_bit(gpio, &pending, BITS_PER_LONG)
> > +		for_each_bit(gpio, &pending, PL061_GPIO_NR)
> >  			generic_handle_irq(gpio_to_irq(gpio));
> >  	}
> >  	desc->chip->unmask(irq);
> >  }
> >  
> > -static void pl061_gpio_free(struct work_struct *work)
> > -{
> > -	struct pl061_gpio *chip = container_of(work, struct pl061_gpio,
> > -			gpio_free_work);
> > -	int offset;
> > -
> > -	for_each_bit(offset, chip->gpios_to_free, PL061_GPIO_NR) {
> > -		int gpio = offset + chip->gc.base;
> > -
> > -		if (test_and_clear_bit(offset, chip->gpios_to_free))
> > -			gpio_free(gpio);
> > -	}
> > -}
> > -
> >  static int __init pl061_probe(struct amba_device *dev, struct amba_id *id)
> >  {
> >  	struct pl061_platform_data *pdata;
> >  	struct pl061_gpio *chip;
> > +	struct list_head *chip_list;
> >  	int ret, irq, i;
> >  
> >  	pdata = dev->dev.platform_data;
> > @@ -251,12 +238,12 @@ static int __init pl061_probe(struct amb
> >  	if (chip == NULL)
> >  		return -ENOMEM;
> >  
> > -	if (request_mem_region(dev->res.start, SZ_4K, "pl061") == NULL) {
> > +	if (!request_mem_region(dev->res.start, PL061_REG_SIZE, "pl061")) {
> >  		ret = -EBUSY;
> >  		goto free_mem;
> >  	}
> >  
> > -	chip->base = ioremap(dev->res.start, SZ_4K);
> > +	chip->base = ioremap(dev->res.start, PL061_REG_SIZE);
> >  	if (chip->base == NULL) {
> >  		ret = -ENOMEM;
> >  		goto release_region;
> > @@ -264,8 +251,7 @@ static int __init pl061_probe(struct amb
> >  
> >  	spin_lock_init(&chip->lock);
> >  	spin_lock_init(&chip->irq_lock);
> > -
> > -	INIT_WORK(&chip->gpio_free_work, pl061_gpio_free);
> > +	INIT_LIST_HEAD(&chip->list);
> >  
> >  	chip->gc.direction_input = pl061_direction_input;
> >  	chip->gc.direction_output = pl061_direction_output;
> > @@ -291,7 +277,17 @@ static int __init pl061_probe(struct amb
> >  		goto iounmap;
> >  	}
> >  	set_irq_chained_handler(irq, pl061_irq_handler);
> > -	pl061_pending_irq = pdata->pending_irqs;
> > +	if (!pdata->is_irq_initialized || !pdata->is_irq_initialized(irq)) {
> > +		chip_list = kmalloc(sizeof(*chip_list), GFP_KERNEL);
> > +		if (chip_list == NULL) {
> > +			ret = -ENOMEM;
> > +			goto iounmap;
> > +		}
> > +		INIT_LIST_HEAD(chip_list);
> > +		set_irq_chip_data(irq, chip_list);
> > +	} else
> > +		chip_list = get_irq_chip_data(irq);
> > +	list_add(&chip->list, chip_list);
> >  
> >  	for (i = 0; i < PL061_GPIO_NR; i++) {
> >  		if (pdata->directions & (1 << i))
> > @@ -312,7 +308,7 @@ static int __init pl061_probe(struct amb
> >  iounmap:
> >  	iounmap(chip->base);
> >  release_region:
> > -	release_mem_region(dev->res.start, SZ_4K);
> > +	release_mem_region(dev->res.start, PL061_REG_SIZE);
> >  free_mem:
> >  	kfree(chip);
> >  
> > diff -puN include/linux/amba/pl061.h~gpio-driver-for-primecell-pl061-gpio-controller-v4 include/linux/amba/pl061.h
> > --- a/include/linux/amba/pl061.h~gpio-driver-for-primecell-pl061-gpio-controller-v4
> > +++ a/include/linux/amba/pl061.h
> > @@ -1,18 +1,17 @@
> >  /* platform data for the PL061 GPIO driver */
> >  
> > -#define GPIODIR 0x400
> > -#define GPIOIS  0x404
> > -#define GPIOIBE 0x408
> > -#define GPIOIEV 0x40C
> > -#define GPIOIE  0x410
> > -#define GPIORIS 0x414
> > -#define GPIOMIS 0x418
> > -#define GPIOIC  0x41C
> > -
> >  struct pl061_platform_data {
> >  	/* number of the first GPIO */
> >  	unsigned	gpio_base;
> > -	u32		(*pending_irqs)(int irq);
> > +
> >  	u8		directions;	/* startup directions, 1: out, 0: in */
> >  	u8		values;		/* startup values */
> > +
> > +	/* This callback may be used when you have more than one PL061
> > +	 * connected to the same IRQ trigger. This callback must return 0 on
> > +	 * the first time it is called for each irq, and 1 on any other call.
> > +	 * In case you are not unfortunate enough to have this setup, this
> > +	 * pointer must be set to NULL.
> > +	 */
> > +	int		(*is_irq_initialized)(int irq);
> >  };
> > _
> > 
> > 

baruch

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