Message-Id: <200812261024.07303.david-b@pacbell.net>
Date:	Fri, 26 Dec 2008 10:24:07 -0800
From:	David Brownell <david-b@...bell.net>
To:	Alessandro Zummo <alessandro.zummo@...ertech.it>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	linux-geode@...ts.infradead.org
Subject: Re: [PATCH] AMD Geode CS553X GPIO driver

On Wednesday 24 December 2008, Alessandro Zummo wrote:
> 
>  A GPIO driver for the AMD Geode CS5535/5536 Companion Devices.

Great -- embedded x86 looking more like embedded rest-of-Linux!  ;)


>  It uses the gpio framework and the gpio api as defined in
>  arch/x86/kernel/geode_32.c

Eventually I'd hope to see those geode_32.c calls just vanish.

In fact, the "normal" way to package these GPIOs would be to
always provide them through the standard API, in arch/... code,
with no Kconfig option.  Any reason you shouldn't do that in
this patch?


>  Patch is against 2.6.28-rc9.
> 
>  Signed-off-by: Alessandro Zummo <a.zummo@...ertech.it>
> 
> 
> ---
>  arch/x86/include/asm/geode.h |   18 ++++
>  drivers/gpio/Kconfig         |   14 +++
>  drivers/gpio/Makefile        |    1 
>  drivers/gpio/cs553x-gpio.c   |  172 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 205 insertions(+)
> 
> --- linux-tuxrouter-2.6.28-rc9.orig/drivers/gpio/Kconfig	2008-12-24 23:34:02.000000000 +0100
> +++ linux-tuxrouter-2.6.28-rc9/drivers/gpio/Kconfig	2008-12-24 23:34:44.000000000 +0100
> @@ -175,4 +175,18 @@ config GPIO_MCP23S08
>  	  SPI driver for Microchip MCP23S08 I/O expander.  This provides
>  	  a GPIO interface supporting inputs and outputs.
>  
> +comment "Other GPIO expanders:"

This counts as "memory mapped" I'd say.  Doesn't need
a new category, even if this does need to live outside
the relevant arch/... files.


> +
> +config GPIO_CS553X
> +	tristate "AMD CS5535/CS5536 Geode Companion Devices"
> +	depends on MGEODE_LX && !CS5535_GPIO

What's this CS5535_GPIO stuff?  And why should it affect
whether this can be configured?  (It's not in mainline...)


> +	help
> +	  Say yes here to provide support for the 28 GPIO pins on
> +	  the AMD CS5535 and CS5536 Geode Companion Devices.
> +
> +	  Your board setup code will have to declare an appropriate
> +	  platform device for this driver to work.
> +
> +	  If unsure, say N.
> +
>  endif
> --- linux-tuxrouter-2.6.28-rc9.orig/drivers/gpio/Makefile	2008-12-24 23:34:02.000000000 +0100
> +++ linux-tuxrouter-2.6.28-rc9/drivers/gpio/Makefile	2008-12-24 23:34:44.000000000 +0100
> @@ -4,6 +4,7 @@ ccflags-$(CONFIG_DEBUG_GPIO)	+= -DDEBUG
>  
>  obj-$(CONFIG_GPIOLIB)		+= gpiolib.o
>  
> +obj-$(CONFIG_GPIO_CS553X)	+= cs553x-gpio.o
>  obj-$(CONFIG_GPIO_MAX7301)	+= max7301.o
>  obj-$(CONFIG_GPIO_MAX732X)	+= max732x.o
>  obj-$(CONFIG_GPIO_MCP23S08)	+= mcp23s08.o
> --- linux-tuxrouter-2.6.28-rc9.orig/arch/x86/include/asm/geode.h	2008-12-24 23:34:02.000000000 +0100
> +++ linux-tuxrouter-2.6.28-rc9/arch/x86/include/asm/geode.h	2008-12-24 23:34:44.000000000 +0100
> @@ -12,6 +12,7 @@
>  
>  #include <asm/processor.h>
>  #include <linux/io.h>
> +#include <linux/platform_device.h>
>  
>  /* Generic southbridge functions */
>  
> @@ -165,6 +166,23 @@ static inline void geode_gpio_event_pme(
>  	geode_gpio_setup_event(gpio, pair, 1);
>  }
>  
> +struct cs553x_gpio_platform_data {
> +
> +	unsigned	gpio_base; /* number of the first GPIO */
> +
> +	resource_size_t	io_base;

Platform devices should use platform_get_resource() and
friends instead of passing resources through platform data.


> +
> +	void		*context; /* param to setup/teardown */
> +
> +	int		(*setup)(struct platform_device *pdev,
> +				unsigned base, unsigned ngpio,
> +				void *context);
> +
> +	int		(*teardown)(struct platform_device *pdev,
> +				unsigned base, unsigned ngpio,
> +				void *context);
> +};
> +
>  /* Specific geode tests */
>  
>  static inline int is_geode_gx(void)


... other than those points, this seems like a simple and
straightforward GPIO driver.  Typical of what arch/* holds
in such cases.  ;)

- Dave



> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ linux-tuxrouter-2.6.28-rc9/drivers/gpio/cs553x-gpio.c	2008-12-24 23:35:41.000000000 +0100
> @@ -0,0 +1,172 @@
> +/*
> + * AMD CS5535/CS5536 Geode Companion Devices GPIO driver
> + *
> + * Copyright (C) 2008 Tower Technologies
> + * Written by Alessandro Zummo <a.zummo@...ertech.it>
> + *
> + * 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
> + */
> +
> +#include <linux/module.h>
> +#include <linux/errno.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/ioport.h>
> +#include <linux/gpio.h>
> +#include <linux/platform_device.h>
> +
> +#include <asm/geode.h>
> +
> +#define DRIVER_NAME "cs553x-gpio"
> +#define DRIVER_VERSION "1.0"
> +
> +static void cs553x_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
> +{
> +	if (value)
> +		geode_gpio_set(geode_gpio(offset), GPIO_OUTPUT_VAL);
> +	else
> +		geode_gpio_clear(geode_gpio(offset), GPIO_OUTPUT_VAL);
> +}
> +
> +static int cs553x_gpio_get(struct gpio_chip *chip, unsigned offset)
> +{
> +	return geode_gpio_isset(geode_gpio(offset), GPIO_READ_BACK);
> +}
> +
> +static int cs553x_direction_input(struct gpio_chip *chip, unsigned offset)
> +{
> +	geode_gpio_clear(geode_gpio(offset), GPIO_OUTPUT_ENABLE);
> +	geode_gpio_set(geode_gpio(offset), GPIO_INPUT_ENABLE);
> +
> +	return 0;
> +}
> +
> +static int cs553x_direction_output(struct gpio_chip *chip, unsigned offset,
> +					int value)
> +{
> +	cs553x_gpio_set(chip, offset, value);
> +
> +	geode_gpio_set(geode_gpio(offset), GPIO_OUTPUT_ENABLE);
> +	geode_gpio_clear(geode_gpio(offset), GPIO_INPUT_ENABLE);
> +
> +	return 0;
> +}
> +
> +static struct gpio_chip cs553x = {
> +	.owner	= THIS_MODULE,
> +	.label	= DRIVER_NAME,
> +	.ngpio	= 28,
> +
> +	.get	= cs553x_gpio_get,
> +	.set	= cs553x_gpio_set,
> +
> +	.direction_input = cs553x_direction_input,
> +	.direction_output = cs553x_direction_output,
> +};
> +
> +
> +static int __init cs553x_gpio_probe(struct platform_device *pdev)
> +{
> +	int rc;
> +	struct cs553x_gpio_platform_data *pdata = pdev->dev.platform_data;
> +
> +	if (pdata == NULL) {
> +		dev_err(&pdev->dev, "missing CS553X platform data\n");
> +		return -ENODEV;
> +	}
> +
> +	if (!pdata->io_base) {
> +		dev_err(&pdev->dev, "platform data has no GPIO base region\n");
> +		return -ENODEV;
> +	}
> +
> +	if (!request_region(pdata->io_base, LBAR_GPIO_SIZE, DRIVER_NAME)) {
> +		dev_err(&pdev->dev, "cannot allocate I/O region at %x\n",
> +				pdata->io_base);
> +		return -ENODEV;
> +	}
> +
> +	cs553x.dev = &pdev->dev;
> +	cs553x.base = pdata->gpio_base;
> +
> +	rc = gpiochip_add(&cs553x);
> +	if (rc < 0) {
> +		dev_err(&pdev->dev, "cannot add GPIO\n");
> +		goto fail_release;
> +	}
> +
> +	dev_info(&pdev->dev, "registered at 0x%x, GPIO base %d\n",
> +			pdata->io_base, cs553x.base);
> +
> +	if (pdata->setup) {
> +		rc = pdata->setup(pdev, cs553x.base,
> +				cs553x.ngpio, pdata->context);
> +
> +		if (rc < 0) {
> +			dev_err(&pdev->dev, "setup failed, %d\n", rc);
> +			goto fail_remove;
> +		}
> +	}
> +
> +	return 0;
> +
> +fail_remove:
> +	gpiochip_remove(&cs553x);
> +
> +fail_release:
> +	release_region(pdata->io_base, LBAR_GPIO_SIZE);
> +
> +	return rc;
> +}
> +
> +static int __exit cs553x_gpio_remove(struct platform_device *pdev)
> +{
> +	struct cs553x_gpio_platform_data *pdata = pdev->dev.platform_data;
> +
> +	if (pdata->teardown) {
> +		int rc = pdata->teardown(pdev, cs553x.base,
> +				cs553x.ngpio, pdata->context);
> +		if (rc < 0) {
> +			dev_err(&pdev->dev, "teardown failed, %d\n", rc);
> +			return rc;
> +		}
> +	}
> +
> +	gpiochip_remove(&cs553x);
> +	release_region(pdata->io_base, LBAR_GPIO_SIZE);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver cs553x_gpio_driver = {
> +	.driver	 = {
> +		.name   = DRIVER_NAME,
> +		.owner  = THIS_MODULE,
> +	},
> +	.remove	 = __exit_p(cs553x_gpio_remove),
> +};
> +
> +static int __init cs553x_gpio_init(void)
> +{
> +	if (!is_geode())
> +		return -ENODEV;
> +
> +	return platform_driver_probe(&cs553x_gpio_driver, cs553x_gpio_probe);
> +}
> +
> +static void __exit cs553x_gpio_exit(void)
> +{
> +	platform_driver_unregister(&cs553x_gpio_driver);
> +}
> +
> +module_init(cs553x_gpio_init);
> +module_exit(cs553x_gpio_exit);
> +
> +
> +MODULE_AUTHOR("Alessandro Zummo <a.zummo@...ertech.it>");
> +MODULE_DESCRIPTION("AMD CS5535/CS5536 GPIO driver");
> +MODULE_LICENSE("GPL");
> +MODULE_VERSION(DRIVER_VERSION);
> +MODULE_ALIAS("platform:cs553x-gpio");
> 
> -- 
> 
>  Best regards,
> 
>  Alessandro Zummo,
>   Tower Technologies - Torino, Italy
> 
>   http://www.towertech.it
> 
> 


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