Date:	Wed, 1 Jul 2009 16:28:08 -0700
From:	David Brownell <david-b@...bell.net>
To:	"Du, Alek" <alek.du@...el.com>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: add Intel Moorestown Platform Langwell chip gpio driver

On Wednesday 01 July 2009, you wrote:
> Sent: 2009年6月30日 13:08
> To: Kernel Mailing List
> Subject: [PATCH] gpio: add Intel Moorestown Platform Langwell chip gpio driver
> 
> From 18d915ac81fd441938225dcaa389b597af483a4f Mon Sep 17 00:00:00 2001
> From: Alek Du <alek.du@...el.com>
> Date: Tue, 30 Jun 2009 12:13:27 +0800
> Subject: [PATCH] gpio: add Intel Moorestown Platform Langwell chip gpio driver
> 
> The Langwell chip has a 64-pin gpio block, which is exposed as a PCI device.

Is this a dedicated GPIO-only device?  Or is it like e.g. ICH8
which shares that device with other functions?


> We use it to control outside peripheral as well as to do IRQ demuxing. The
> gpio block uses MSI to request level type interrupt to IOAPIC.
> 
> Signed-off-by: Alek Du <alek.du@...el.com>
> ---
>  drivers/gpio/Kconfig  |    6 +
>  drivers/gpio/Makefile |    1 +
>  drivers/gpio/lnw.c    |  360 +++++++++++++++++++++++++++++++++++++++++++++++++

So if LNG is Liquid Natural Gass, then LNW is ... Liquid Natural Water??

Spell it out please.  And use the same name in the driver.name too.


>  3 files changed, 367 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/gpio/lnw.c
> 
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 3582c39..c9675de 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -167,6 +167,12 @@ config GPIO_BT8XX
>  
>  	  If unsure, say N.
>  
> +config GPIO_LANGWELL
> +	tristate "Intel Moorestown Platform Langwell GPIO support"
> +	depends on PCI
> +	help
> +	  Say Y here to support Intel Moorestown platform GPIO.
> +
>  comment "SPI GPIO expanders:"
>  
>  config GPIO_MAX7301
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index ef90203..d8ee188 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -13,3 +13,4 @@ obj-$(CONFIG_GPIO_PL061)	+= pl061.o
>  obj-$(CONFIG_GPIO_TWL4030)	+= twl4030-gpio.o
>  obj-$(CONFIG_GPIO_XILINX)	+= xilinx_gpio.o
>  obj-$(CONFIG_GPIO_BT8XX)	+= bt8xxgpio.o
> +obj-$(CONFIG_GPIO_LANGWELL)	+= lnw.o
> diff --git a/drivers/gpio/lnw.c b/drivers/gpio/lnw.c
> new file mode 100644
> index 0000000..d437fe0
> --- /dev/null
> +++ b/drivers/gpio/lnw.c
> @@ -0,0 +1,360 @@
> +/* lnw.c Moorestown platform Langwell chip GPIO driver
> + * Copyright (c) 2008 - 2009,  Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + */
> +
> +/* Supports:
> + * Moorestown platform Langwell chip.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/kernel.h>
> +#include <linux/delay.h>
> +#include <linux/stddef.h>
> +#include <linux/interrupt.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/gpio.h>
> +
> +#ifdef CONFIG_DEBUG_GPIO
> +#define GDEBUG(format, arg...) printk(KERN_DEBUG format, ## arg)
> +#else
> +#define GDEBUG(format, arg...)
> +#endif

Get rid of GDEBUG.  The drivers/gpio/Makefile sets up
the standard "-DDEBUG" if that Kconfig symbol is set,
so you can use pr_debug(), dev_dbg(), or dev_vdbg().


> +
> +#define GPIO_bit(gpio) (1 << ((gpio) & 0x1f))

Style-wise:  avoid MiXeD_CaSE symbols.  "BIT(gpio % 32)"
seems pretty simple ... I'd personally avoid macros for
anything that simple.


> +
> +struct lnw_gpio_register {
> +	u32	GPLR0;
> +	u32	GPLR1;
> +	u32	GPDR0;
> +	u32	GPDR1;
> +	u32	GPSR0;
> +	u32	GPSR1;
> +	u32	GPCR0;
> +	u32	GPCR1;
> +	u32	GRER0;
> +	u32	GRER1;
> +	u32	GFER0;
> +	u32	GFER1;
> +	u32	GEDR0;
> +	u32	GEDR1;

For all those, your usage in the code better matches a

	u32	GxxR[2];

style declaration...


> +	u32	GAFR0_L;
> +	u32	GAFR0_U;
> +	u32	GAFR1_L;
> +	u32	GAFR1_U;
> +};

You're sure this isn't like a trimmed-down PXA part?
I think I know some of the history of that register
model ...  :)


> +
> +struct lnw_gpio {
> +	struct gpio_chip		chip;
> +	struct lnw_gpio_register 	*reg_base;
> +	spinlock_t			lock;
> +	unsigned			irq_base;
> +};
> +
> +static int lnw_gpio_get(struct gpio_chip *chip, unsigned offset)
> +{
> +	struct lnw_gpio *lnw = container_of(chip, struct lnw_gpio, chip);
> +	u8 reg = offset / 32;
> +	void __iomem *gplr;
> +
> +	gplr = (void __iomem *)(&lnw->reg_base->GPLR0 + reg);
> +	return readl(gplr) & GPIO_bit(offset);
> +}
> +
> +static void lnw_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
> +{
> +	struct lnw_gpio *lnw = container_of(chip, struct lnw_gpio, chip);
> +	u8 reg = offset / 32;
> +	void __iomem *gpsr, *gpcr;
> +
> +	if (value) {
> +		gpsr = (void __iomem *)(&lnw->reg_base->GPSR0 + reg);
> +		writel(GPIO_bit(offset), gpsr);
> +	} else {
> +		gpcr = (void __iomem *)(&lnw->reg_base->GPCR0 + reg);
> +		writel(GPIO_bit(offset), gpcr);
> +	}
> +}
> +
> +static int lnw_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
> +{
> +	struct lnw_gpio *lnw = container_of(chip, struct lnw_gpio, chip);
> +	u8 reg = offset / 32;
> +	u32 value;
> +	unsigned long flags;
> +	void __iomem *gpdr;
> +
> +	gpdr = (void __iomem *)(&lnw->reg_base->GPDR0 + reg);
> +	spin_lock_irqsave(&lnw->lock, flags);
> +	value = readl(gpdr);
> +	value &= ~GPIO_bit(offset);
> +	writel(value, gpdr);
> +	spin_unlock_irqrestore(&lnw->lock, flags);
> +	return 0;
> +}
> +
> +static int lnw_gpio_direction_output(struct gpio_chip *chip,
> +			unsigned offset, int value)
> +{
> +	struct lnw_gpio *lnw = container_of(chip, struct lnw_gpio, chip);
> +	u8 reg = offset / 32;
> +	unsigned long flags;
> +	void __iomem *gpdr;
> +
> +	lnw_gpio_set(chip, offset, value);
> +	gpdr = (void __iomem *)(&lnw->reg_base->GPDR0 + reg);
> +	spin_lock_irqsave(&lnw->lock, flags);
> +	value = readl(gpdr);
> +	value |= GPIO_bit(offset);;
> +	writel(value, gpdr);
> +	spin_unlock_irqrestore(&lnw->lock, flags);
> +	return 0;
> +}
> +
> +static void lnw_gpio_alt_func(struct gpio_chip *chip,
> +			unsigned offset, int value)

Not a standard gpiochip method, so it should really be
in some other group of methods.  And with-comment.


> +{
> +	struct lnw_gpio *lnw = container_of(chip, struct lnw_gpio, chip);
> +	u8 reg = offset / 16;
> +	u32 mask = 3 << ((offset % 16) * 2);
> +	unsigned long flags;
> +	void __iomem *gafr;
> +
> +	value = (value & 3) << ((offset % 16) * 2);
> +	gafr = (void __iomem *)(&lnw->reg_base->GAFR0_L + reg);
> +	spin_lock_irqsave(&lnw->lock, flags);
> +	writel((readl(gafr) & ~mask) | value, gafr);
> +	spin_unlock_irqrestore(&lnw->lock, flags);
> +}
> +
> +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;
> +}
> +
> +static int lnw_irq_type(unsigned irq, unsigned type)
> +{
> +	struct lnw_gpio *lnw = get_irq_chip_data(irq);
> +	u32 gpio = irq - lnw->irq_base;
> +	u8 reg = gpio / 32;
> +	unsigned long flags;
> +	u32 value;
> +	void __iomem *grer = (void __iomem *)(&lnw->reg_base->GRER0 + reg);
> +	void __iomem *gfer = (void __iomem *)(&lnw->reg_base->GFER0 + reg);
> +
> +	if (gpio < 0 || gpio > lnw->chip.ngpio)
> +		return -EINVAL;
> +	lnw_gpio_alt_func(&lnw->chip, gpio, 0);

If it's not *already* set up as a GPIO this is a bug in the
calling code.  You shouldn't need to set the alt func.


> +	spin_lock_irqsave(&lnw->lock, flags);
> +	if (type & IRQ_TYPE_EDGE_RISING)
> +		value = readl(grer) | GPIO_bit(gpio);
> +	else
> +		value = readl(grer) & (~GPIO_bit(gpio));
> +	writel(value, grer);
> +
> +	if (type & IRQ_TYPE_EDGE_FALLING)
> +		value = readl(gfer) | GPIO_bit(gpio);
> +	else
> +		value = readl(gfer) & (~GPIO_bit(gpio));
> +	writel(value, gfer);
> +	spin_unlock_irqrestore(&lnw->lock, flags);
> +
> +	return 0;
> +};
> +
> +static void lnw_irq_unmask(unsigned irq)
> +{
> +	struct lnw_gpio *lnw = get_irq_chip_data(irq);
> +	u32 gpio = irq - lnw->irq_base;
> +	u8 reg = gpio / 32;
> +	void __iomem *gedr;
> +
> +	gedr = (void __iomem *)(&lnw->reg_base->GEDR0 + reg);
> +	writel(GPIO_bit(gpio), gedr);
> +};
> +
> +static struct irq_chip lnw_irqchip = {
> +	.name		= "LNW-GPIO",
> +	.unmask		= lnw_irq_unmask,
> +	.set_type	= lnw_irq_type,
> +};
> +
> +struct lnw_driver_data {
> +	unsigned	gpio_base;
> +	unsigned	gpio_nr;
> +} lnw_driver_datas[] __devinitdata = {
> +	{ .gpio_base = 0, .gpio_nr = 64 },

Hmm, passing gpio_base here is kind of ugly.

But I guess you're working with platforms that don't
really have good ways to pass platform-specific data
through device->platform_data, so you're stuck with
being ugly...


> +	{ 0 }
> +};
> +
> +static struct pci_device_id lnw_gpio_ids[] = {
> +	{ PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0x080f),
> +	  .driver_data = (unsigned long)&lnw_driver_datas[0] },
> +	{ 0, }
> +};
> +
> +static void lnw_irq_handler(unsigned irq, struct irq_desc *desc)
> +{
> +	struct lnw_gpio *lnw = (struct lnw_gpio *)get_irq_data(irq);
> +	u32 reg, gpio;
> +	void __iomem *gedr;
> +	u32 gedr_v;
> +
> +	/* check GPIO controller to check which pin triggered the interrupt */
> +	for (reg = 0; reg < lnw->chip.ngpio / 32; reg++) {
> +		gedr = (void __iomem *)(&lnw->reg_base->GEDR0 + reg);
> +		gedr_v = readl(gedr);
> +		if (!gedr_v)
> +			continue;
> +		for (gpio = reg*32; gpio < reg*32+32; gpio++) {
> +			gedr_v = readl(gedr);
> +			if (gedr_v & GPIO_bit(gpio)) {
> +				GDEBUG("pin %d triggered\n", gpio);
> +				generic_handle_irq(lnw->irq_base + gpio);
> +			}
> +		}
> +		/* clear the edge detect status bit */
> +		writel(gedr_v, gedr);
> +	}
> +	desc->chip->eoi(irq);
> +}
> +
> +static int __devinit lnw_gpio_probe(struct pci_dev *pdev,
> +			const struct pci_device_id *id)
> +{
> +	void *base;
> +	int i;
> +	resource_size_t start, len;
> +	struct lnw_gpio *lnw;
> +	u32 irq_base;
> +	struct lnw_driver_data *ddata =
> +			(struct lnw_driver_data *)id->driver_data;
> +	int retval = 0;
> +
> +	retval = pci_enable_device(pdev);
> +	if (retval)
> +		goto done;
> +
> +	retval = pci_request_regions(pdev, "lnwgpio");
> +	if (retval) {
> +		dev_err(&pdev->dev, "error requesting resources\n");
> +		goto err2;
> +	}
> +	start = pci_resource_start(pdev, 1);
> +	len = pci_resource_len(pdev, 1);
> +	base = ioremap_nocache(start, len);
> +	if (!base) {
> +		dev_err(&pdev->dev, "error mapping bar1\n");
> +		goto err3;
> +	}
> +	irq_base = *(u32 *)base;
> +	iounmap(base);/* we needn't it anymore */

Don't need it?  Comment *why* then ...


> +
> +	start = pci_resource_start(pdev, 0);
> +	len = pci_resource_len(pdev, 0);
> +	base = ioremap_nocache(start, len);
> +	if (!base) {
> +		dev_err(&pdev->dev, "error mapping bar0\n");
> +		retval = -EFAULT;
> +		goto err3;
> +	}
> +
> +	lnw = kzalloc(sizeof(struct lnw_gpio), GFP_KERNEL);
> +	if (!lnw) {
> +		dev_err(&pdev->dev, "can not allocate lnw_gpio chip data\n");
> +		retval = -ENOMEM;
> +		goto err4;
> +	}
> +	lnw->reg_base = base;
> +	lnw->irq_base = irq_base;
> +	lnw->chip.label = dev_name(&pdev->dev);
> +	lnw->chip.direction_input = lnw_gpio_direction_input;
> +	lnw->chip.direction_output = lnw_gpio_direction_output;
> +	lnw->chip.get = lnw_gpio_get;
> +	lnw->chip.set = lnw_gpio_set;
> +	lnw->chip.to_irq = lnw_gpio_to_irq;
> +	lnw->chip.base = ddata->gpio_base;
> +	lnw->chip.ngpio = ddata->gpio_nr;
> +	lnw->chip.can_sleep = 0;
> +	pci_set_drvdata(pdev, lnw);
> +	retval = gpiochip_add(&lnw->chip);
> +	if (retval) {
> +		dev_err(&pdev->dev, "lnw gpiochip_add error %d\n", retval);
> +		goto err5;
> +	}
> +	set_irq_data(pdev->irq, lnw);
> +	set_irq_chained_handler(pdev->irq, lnw_irq_handler);
> +	for (i = 0; i < lnw->chip.ngpio; i++) {
> +		set_irq_chip_and_handler_name(i + lnw->irq_base, &lnw_irqchip,
> +					handle_edge_irq, "demux");
> +		set_irq_chip_data(i + lnw->irq_base, lnw);
> +	}
> +
> +	spin_lock_init(&lnw->lock);
> +	goto done;
> +err5:
> +	kfree(lnw);
> +err4:
> +	iounmap(base);
> +err3:
> +	pci_release_regions(pdev);
> +err2:
> +	pci_disable_device(pdev);
> +done:
> +	return retval;
> +}
> +
> +static void __devexit lnw_gpio_remove(struct pci_dev *pdev)
> +{
> +	struct lnw_gpio *lnw = (struct lnw_gpio *)pci_get_drvdata(pdev);
> +
> +	if (gpiochip_remove(&lnw->chip)) {
> +		dev_err(&pdev->dev, "lnw gpio driver remove error\n");
> +		return;
> +	}
> +	pci_disable_device(pdev);
> +	set_irq_chained_handler(pdev->irq, NULL);
> +	pci_release_regions(pdev);
> +	iounmap(lnw->reg_base);
> +	pci_set_drvdata(pdev, NULL);
> +	kfree(lnw);
> +}
> +
> +static struct pci_driver lnw_gpio_driver = {
> +	.name		= "Langwell GPIO driver",

Better just "langwell_gpio" for this, and
"langwell_gpio.c" for the name of the source file.


> +	.id_table	= lnw_gpio_ids,
> +	.probe		= lnw_gpio_probe,
> +	.remove		= lnw_gpio_remove,
> +};
> +
> +static int __init lnw_gpio_init(void)
> +{
> +	return pci_register_driver(&lnw_gpio_driver);
> +}
> +
> +static void __exit lnw_gpio_exit(void)
> +{
> +	pci_unregister_driver(&lnw_gpio_driver);
> +}
> +
> +MODULE_AUTHOR("Alek Du <alek.du@...el.com>");
> +MODULE_DESCRIPTION("Intel Moorestown Platform Langwell chip GPIO driver");
> +MODULE_LICENSE("GPL v2");
> +
> +module_init(lnw_gpio_init);
> +module_exit(lnw_gpio_exit);
> 

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