Subject: Re: [PATCH 2/2] i2c: Add devtree-aware iic support for PPC4xx

From: Valentine Barshak <[email-masked]>
Date: Fri, 19 Oct 2007 15:56:40 +0400

Please, take a look at my comments below

Stefan Roese wrote:
> This patch reworks existing ibm-iic driver to support of_platform_device
> and enables it to talk to device tree directly. The "old" OCP interface
> for arch/ppc is still supported via #ifdef's and shall be removed when
> arch/ppc is gone in a few months.
> 
> This is done to enable I2C support for the PPC4xx platforms now
> being moved from arch/ppc (ocp) to arch/powerpc (of).
> 
> Signed-off-by: Stefan Roese <[email-masked]>
> ---
>  drivers/i2c/busses/Kconfig       |    2 +-
>  drivers/i2c/busses/i2c-ibm_iic.c |  209 +++++++++++++++++++++++++++++++++++++-
>  drivers/i2c/busses/i2c-ibm_iic.h |    2 +
>  3 files changed, 211 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index de95c75..a47b5e6 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -241,7 +241,7 @@ config I2C_PIIX4
>  
>  config I2C_IBM_IIC
>  	tristate "IBM PPC 4xx on-chip I2C interface"
> -	depends on IBM_OCP
> +	depends on 4xx
>  	help
>  	  Say Y here if you want to use IIC peripheral found on 
>  	  embedded IBM PPC 4xx based systems. 
> diff --git a/drivers/i2c/busses/i2c-ibm_iic.c b/drivers/i2c/busses/i2c-ibm_iic.c
> index 956b947..78c6bf4 100644
> --- a/drivers/i2c/busses/i2c-ibm_iic.c
> +++ b/drivers/i2c/busses/i2c-ibm_iic.c
> @@ -39,8 +39,13 @@
>  #include <asm/io.h>
>  #include <linux/i2c.h>
>  #include <linux/i2c-id.h>
> +
> +#ifdef CONFIG_PPC_MERGE
> +#include <linux/of_platform.h>
> +#else
>  #include <asm/ocp.h>
>  #include <asm/ibm4xx.h>
> +#endif
>  
>  #include "i2c-ibm_iic.h"
>  
> @@ -57,6 +62,10 @@ static int iic_force_fast;
>  module_param(iic_force_fast, bool, 0);
>  MODULE_PARM_DESC(iic_fast_poll, "Force fast mode (400 kHz)");
>  
> +#ifdef CONFIG_PPC_MERGE
> +static int device_idx = -1;
> +#endif
> +
>  #define DBG_LEVEL 0
>  
>  #ifdef DBG
> @@ -660,8 +669,205 @@ static inline u8 iic_clckdiv(unsigned int opb)
>  /*
>   * Register single IIC interface
>   */
> -static int __devinit iic_probe(struct ocp_device *ocp){
>  
> +#ifdef CONFIG_PPC_MERGE
> +/*
> + * device-tree (of) when used from arch/powerpc
> + */
> +static int __devinit iic_probe(struct of_device *ofdev,
> +			       const struct of_device_id *match)
> +{
> +	struct ibm_iic_private* dev;
> +	struct i2c_adapter* adap;
> +	struct device_node *np;
> +	int ret = -ENODEV;
> +	int  irq, len;
> +	const u32 *prop;
> +	struct resource res;
> +
> +	np = ofdev->node;
> +	if (!(dev = kzalloc(sizeof(*dev), GFP_KERNEL))) {
> +		printk(KERN_CRIT "ibm-iic(%s): failed to allocate device data\n",
> +		       np->full_name);
> +		return -ENOMEM;
> +	}
> +
> +	dev_set_drvdata(&ofdev->dev, dev);
> +
> +	dev->np = np;
> +	irq = irq_of_parse_and_map(np, 0);

In case of an error irq might be NO_IRQ here (0)
This could cause problems in chacking the mode (irq or poll) later.

> +
> +	if (of_address_to_resource(np, 0, &res)) {
> +		printk(KERN_ERR "ibd-iic(%s): Can't get registers address\n",
> +		       np->full_name);
> +		goto fail1;
> +	}
> +	dev->paddr = res.start;
> +
> +	if (!request_mem_region(dev->paddr, sizeof(struct iic_regs), "ibm_iic")) {
> +		ret = -EBUSY;
> +		goto fail1;
> +	}
> +	dev->vaddr = ioremap(dev->paddr, sizeof(struct iic_regs));
> +
> +	if (dev->vaddr == NULL) {
> +		printk(KERN_CRIT "ibm-iic(%s): failed to ioremap device regs\n",
> +		       dev->np->full_name);
> +		ret = -ENXIO;
> +		goto fail2;
> +	}
> +
> +	init_waitqueue_head(&dev->wq);
> +
> +	dev->irq = iic_force_poll ? -1 : (irq == NO_IRQ) ? -1 : irq;
> +	if (dev->irq >= 0){

If irq equals NO_IRQ (irq == 0) we shouldn't assume interrupt mode here.
I'd suggest to update the driver to use (irq != NO_IRQ) checks instead 
of (irq >=0)

> +		/* Disable interrupts until we finish initialization,
> +		 * assumes level-sensitive IRQ setup...
> +		 */
> +		iic_interrupt_mode(dev, 0);
> +		if (request_irq(dev->irq, iic_handler, 0, "IBM IIC", dev)) {
> +			printk(KERN_ERR "ibm-iic(%s): request_irq %d failed\n",
> +			       dev->np->full_name, dev->irq);
> +			/* Fallback to the polling mode */
> +			dev->irq = -1;
> +		}
> +	}
> +
> +	if (dev->irq < 0)
> +		printk(KERN_WARNING "ibm-iic(%s): using polling mode\n",
> +		       dev->np->full_name);
> +
> +	/* Board specific settings */
> +	prop = of_get_property(np, "iic-mode", &len);
> +	/* use 400kHz only if stated in dts, 100kHz otherwise */
> +	dev->fast_mode = (prop && (*prop == 400));
> +	/* clckdiv is the same for *all* IIC interfaces,
> +	 * but I'd rather make a copy than introduce another global. --ebs
> +	 */
> +	/* Parent bus should have frequency filled */
> +	prop = of_get_property(of_get_parent(np), "clock-frequency", &len);
> +	if (prop == NULL) {
> +		printk(KERN_ERR
> +		       "ibm-iic(%s):no clock-frequency prop on parent bus!\n",
> +		       dev->np->full_name);
> +		goto fail;
> +	}
> +
[ snip ]
> +	dev->clckdiv = iic_clckdiv(*prop);
> +	DBG("%s: clckdiv = %d\n", dev->np->full_name, dev->clckdiv);
> +
> +	/* Initialize IIC interface */
> +	iic_dev_init(dev);
> +
> +	/* Register it with i2c layer */
> +	adap = &dev->adap;
> +	adap->dev.parent = &ofdev->dev;
> +	strcpy(adap->name, "IBM IIC");
> +	i2c_set_adapdata(adap, dev);
> +	adap->id = I2C_HW_OCP;
> +	adap->class = I2C_CLASS_HWMON;
> +	adap->algo = &iic_algo;
> +	adap->client_register = NULL;
> +	adap->client_unregister = NULL;
> +	adap->timeout = 1;
> +	adap->retries = 1;
> +
> +	dev->idx = ++device_idx;
> +	adap->nr = dev->idx;
> +	if ((ret = i2c_add_numbered_adapter(adap)) < 0) {
[ snip ]

This stuff might be extracted into the common init function.
Something like this:

static int iic_adap_add(struct ibm_iic_private *dev, unsigned int opb)
{
	struct i2c_adapter *adap;

	/* clckdiv is the same for *all* IIC interfaces,
	 * but I'd rather make a copy than introduce another global. --ebs
	 */
	dev->clckdiv = iic_clckdiv(opb);
	DBG("%d: clckdiv = %d\n", dev->idx, dev->clckdiv);

	/* Initialize IIC interface */
	iic_dev_init(dev);

	/* Register it with i2c layer */
	adap = &dev->adap;
	strcpy(adap->name, "IBM IIC");
	i2c_set_adapdata(adap, dev);
	adap->id = I2C_HW_OCP;
	adap->class = I2C_CLASS_HWMON;
	adap->algo = &iic_algo;
	adap->client_register = NULL;
	adap->client_unregister = NULL;
	adap->timeout = 1;
	adap->retries = 1;
	return i2c_add_adapter(adap);
}

Though, I really don't care, since OCP part is dying.

> +		printk(KERN_CRIT"ibm-iic(%s): failed to register i2c adapter\n",
> +		       dev->np->full_name);
> +		goto fail;
> +	}
> +
> +	printk(KERN_INFO "ibm-iic(%s): using %s mode\n", dev->np->full_name,
> +	       dev->fast_mode ?
> +	       "fast (400 kHz)" : "standard (100 kHz)");
> +
> +	return 0;
> +
> +fail:
> +	if (dev->irq >= 0){
> +		iic_interrupt_mode(dev, 0);
> +		free_irq(dev->irq, dev);

Please, add a call to irq_dispose_mapping(dev->irq);

> +	}
> +
> +	iounmap(dev->vaddr);
> +fail2:
> +	release_mem_region(dev->paddr, sizeof(struct iic_regs));
> +fail1:
> +	dev_set_drvdata(&ofdev->dev, NULL);
> +	kfree(dev);
> +
> +	return ret;
> +}
> +
> +/*
> + * Cleanup initialized IIC interface
> + */
> +static int __devexit iic_remove(struct of_device *ofdev)
> +{
> +	struct ibm_iic_private *dev =
> +		(struct ibm_iic_private *)dev_get_drvdata(&ofdev->dev);
> +	BUG_ON(dev == NULL);
> +	if (i2c_del_adapter(&dev->adap)){
> +		printk(KERN_CRIT "ibm-iic(%s): failed to delete i2c adapter\n",
> +		       dev->np->full_name);
> +		/* That's *very* bad, just shutdown IRQ ... */
> +		if (dev->irq >= 0){
> +			iic_interrupt_mode(dev, 0);
> +			free_irq(dev->irq, dev);
> +			dev->irq = -1;
> +		}
> +	} else {
> +		if (dev->irq >= 0){
> +			iic_interrupt_mode(dev, 0);
> +			free_irq(dev->irq, dev);
> +		}

This can be reorganized to switch to poll mode, diapose irq and check 
i2c_del_adapter retval after that, instead of duplicating the free_irq 
stuff.
Also irq_dispose_mapping(dev->irq); should be added:
.........
	int retval;

	retval = i2c_del_adapter(&dev->adap);
	if (dev->irq != NO_IRQ) {
		iic_interrupt_mode(dev, 0);
		free_irq(dev->irq, dev);
		irq_dispose_mapping(dev->irq);
	}

	if (retval) {
		printk(KERN_CRIT "ibm-iic(%s): failed to delete i2c adapter :(\n",
			dev->np->full_name);
		/* That's *very* bad, just shutdown IRQ ... */
		dev->irq = NO_IRQ;
		return 0;
	}
	iounmap(dev->vaddr);
.......

> +		iounmap(dev->vaddr);
> +		release_mem_region(dev->paddr, sizeof(struct iic_regs));
> +		kfree(dev);
> +	}
> +	return 0;
> +}
> +
> +static struct of_device_id ibm_iic_match[] = {
> +	{
> +		.type = "i2c",
> +		.compatible = "ibm,iic",
> +	},
> +	{},
> +};
> +
> +MODULE_DEVICE_TABLE(of, ibm_iic_match);
> +
> +static struct of_platform_driver ibm_iic_driver = {
> +	.name = "ibm-iic",
> +	.match_table = ibm_iic_match,
> +	.probe = iic_probe,
> +	.remove = iic_remove,
> +#if defined(CONFIG_PM)
> +	.suspend = NULL,
> +	.resume = NULL,
> +#endif
> +};
> +
> +static int __init iic_init(void)
> +{
> +	printk(KERN_INFO "IBM IIC driver v" DRIVER_VERSION "\n");
> +	return of_register_platform_driver(&ibm_iic_driver);
> +}
> +
> +static void __exit iic_exit(void)
> +{
> +	of_unregister_platform_driver(&ibm_iic_driver);
> +}
> +#else
> +/*
> + * OCP when used from arch/ppc
> + */
> +static int __devinit iic_probe(struct ocp_device *ocp)
> +{
>  	struct ibm_iic_private* dev;
>  	struct i2c_adapter* adap;
>  	struct ocp_func_iic_data* iic_data = ocp->def->additions;
> @@ -828,6 +1034,7 @@ static void __exit iic_exit(void)
>  {
>  	ocp_unregister_driver(&ibm_iic_driver);
>  }
> +#endif /* CONFIG_PPC_MERGE */
>  
>  module_init(iic_init);
>  module_exit(iic_exit);
> diff --git a/drivers/i2c/busses/i2c-ibm_iic.h b/drivers/i2c/busses/i2c-ibm_iic.h
> index fdaa482..c15b091 100644
> --- a/drivers/i2c/busses/i2c-ibm_iic.h
> +++ b/drivers/i2c/busses/i2c-ibm_iic.h
> @@ -50,6 +50,8 @@ struct ibm_iic_private {
>  	int irq;
>  	int fast_mode;
>  	u8  clckdiv;
> +	struct device_node *np;
> +	phys_addr_t paddr;
>  };
>  
>  /* IICx_CNTL register */

Thanks,
Valentine.