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Date:	Mon, 01 Sep 2014 09:58:55 +0530
From:	Pankaj Dubey <pankaj.dubey@...sung.com>
To:	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	kgene.kim@...sung.com, linux@....linux.org.uk, arnd@...db.de,
	vikas.sajjan@...sung.com, joshi@...sung.com, naushad@...sung.com,
	thomas.ab@...sung.com, chow.kim@...sung.com,
	'Tomasz Figa' <t.figa@...sung.com>,
	Lee Jones <lee.jones@...aro.org>,
	Tomasz Figa <tomasz.figa@...il.com>
Subject: RE: [PATCH] mfd: syscon: Decouple syscon interface from syscon devices

Sorry I forgot to add maintainer into CC. 

+Lee Jones

Any comments on this patch. 
As a lot of Exynos PMU patch sets are dependent on this patch.

Thanks,
Pankaj Dubey
	

> -----Original Message-----
> From: Pankaj Dubey [mailto:pankaj.dubey@...sung.com]
> Sent: Friday, August 22, 2014 1:40 PM
> To: linux-arm-kernel@...ts.infradead.org;
linux-samsung-soc@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Cc: kgene.kim@...sung.com; linux@....linux.org.uk; arnd@...db.de;
> vikas.sajjan@...sung.com; joshi@...sung.com; naushad@...sung.com;
> thomas.ab@...sung.com; chow.kim@...sung.com; Tomasz Figa; Pankaj Dubey
> Subject: [PATCH] mfd: syscon: Decouple syscon interface from syscon
devices
> 
> From: Tomasz Figa <t.figa@...sung.com>
> 
> Currently a syscon entity can be only registered directly through a
platform device
> that binds to a dedicated driver. However in certain use cases it is
desirable to make a
> device used with another driver a syscon interface provider. For example,
certain
> SoCs (e.g. Exynos) contain system controller blocks which perform various
functions
> such as power domain control, CPU power management, low power mode
control,
> but in addition contain certain IP integration glue, such as various
signal masks,
> coprocessor power control, etc. In such case, there is a need to have a
dedicated
> driver for such system controller but also share registers with other
drivers. The latter
> is where the syscon interface is helpful.
> 
> This patch decouples syscon object from syscon driver, so that it can be
registered
> from any driver in addition to the original "syscon" platform driver.
> 
> Signed-off-by: Tomasz Figa <t.figa@...sung.com>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> ---
> 
> RFC patch [1] was posted by Tomasz Figa. This patch addresses some of
comments
> given by Arnd to RFC patch, and further decouples syscon from device
model. It also
> gives flexibility of registering with syscon at early stage using
device_node object.
> 
> [1]: https://lkml.org/lkml/2014/6/17/331
> 
>  drivers/mfd/syscon.c       |  112 ++++++++++++++++++++++++++++----
> ------------
>  include/linux/mfd/syscon.h |   14 ++++++
>  2 files changed, 86 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c index
ca15878..a91db30
> 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -14,6 +14,7 @@
> 
>  #include <linux/err.h>
>  #include <linux/io.h>
> +#include <linux/list.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/of_address.h>
> @@ -22,33 +23,32 @@
>  #include <linux/platform_device.h>
>  #include <linux/regmap.h>
>  #include <linux/mfd/syscon.h>
> +#include <linux/slab.h>
> 
> -static struct platform_driver syscon_driver;
> +static DEFINE_SPINLOCK(syscon_list_slock);
> +static LIST_HEAD(syscon_list);
> 
>  struct syscon {
> +	struct device_node *np;
>  	struct regmap *regmap;
> +	struct list_head list;
>  };
> 
> -static int syscon_match_node(struct device *dev, void *data) -{
> -	struct device_node *dn = data;
> -
> -	return (dev->of_node == dn) ? 1 : 0;
> -}
> -
>  struct regmap *syscon_node_to_regmap(struct device_node *np)  {
> -	struct syscon *syscon;
> -	struct device *dev;
> +	struct syscon *entry, *syscon = NULL;
> 
> -	dev = driver_find_device(&syscon_driver.driver, NULL, np,
> -				 syscon_match_node);
> -	if (!dev)
> -		return ERR_PTR(-EPROBE_DEFER);
> +	spin_lock(&syscon_list_slock);
> 
> -	syscon = dev_get_drvdata(dev);
> +	list_for_each_entry(entry, &syscon_list, list)
> +		if (entry->np == np) {
> +			syscon = entry;
> +			break;
> +		}
> 
> -	return syscon->regmap;
> +	spin_unlock(&syscon_list_slock);
> +
> +	return syscon ? syscon->regmap : ERR_PTR(-EPROBE_DEFER);
>  }
>  EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
> 
> @@ -68,24 +68,22 @@ struct regmap
> *syscon_regmap_lookup_by_compatible(const char *s)  }
> EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
> 
> -static int syscon_match_pdevname(struct device *dev, void *data) -{
> -	return !strcmp(dev_name(dev), (const char *)data);
> -}
> -
>  struct regmap *syscon_regmap_lookup_by_pdevname(const char *s)  {
> -	struct device *dev;
> -	struct syscon *syscon;
> -
> -	dev = driver_find_device(&syscon_driver.driver, NULL, (void *)s,
> -				 syscon_match_pdevname);
> -	if (!dev)
> -		return ERR_PTR(-EPROBE_DEFER);
> -
> -	syscon = dev_get_drvdata(dev);
> +	struct syscon *entry, *syscon = NULL;
> +	struct platform_device *pdev = NULL;
> +
> +	spin_lock(&syscon_list_slock);
> +	list_for_each_entry(entry, &syscon_list, list) {
> +		 pdev = of_find_device_by_node(entry->np);
> +		if (pdev && !strcmp(dev_name(&pdev->dev), s)) {
> +			syscon = entry;
> +			break;
> +		}
> +	}
> +	spin_unlock(&syscon_list_slock);
> 
> -	return syscon->regmap;
> +	return syscon ? syscon->regmap : ERR_PTR(-EPROBE_DEFER);
>  }
>  EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_pdevname);
> 
> @@ -121,17 +119,49 @@ static struct regmap_config syscon_regmap_config = {
>  	.reg_stride = 4,
>  };
> 
> +void of_syscon_unregister(struct device_node *np) {
> +	struct syscon *entry;
> +
> +	spin_lock(&syscon_list_slock);
> +
> +	list_for_each_entry(entry, &syscon_list, list)
> +		if (entry->np == np) {
> +			list_del(&entry->list);
> +			break;
> +		}
> +
> +	spin_unlock(&syscon_list_slock);
> +}
> +EXPORT_SYMBOL_GPL(of_syscon_unregister);
> +
> +int of_syscon_register(struct device_node *np, struct regmap *regmap) {
> +	struct syscon *syscon;
> +
> +	syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
> +	if (!syscon)
> +		return -ENOMEM;
> +
> +	syscon->regmap = regmap;
> +	syscon->np = np;
> +
> +	spin_lock(&syscon_list_slock);
> +	list_add_tail(&syscon->list, &syscon_list);
> +	spin_unlock(&syscon_list_slock);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_syscon_register);
> +
>  static int syscon_probe(struct platform_device *pdev)  {
>  	struct device *dev = &pdev->dev;
>  	struct syscon_platform_data *pdata = dev_get_platdata(dev);
> -	struct syscon *syscon;
> +	struct regmap *regmap;
>  	struct resource *res;
>  	void __iomem *base;
> -
> -	syscon = devm_kzalloc(dev, sizeof(*syscon), GFP_KERNEL);
> -	if (!syscon)
> -		return -ENOMEM;
> +	int ret;
> 
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	if (!res)
> @@ -144,14 +174,16 @@ static int syscon_probe(struct platform_device
*pdev)
>  	syscon_regmap_config.max_register = res->end - res->start - 3;
>  	if (pdata)
>  		syscon_regmap_config.name = pdata->label;
> -	syscon->regmap = devm_regmap_init_mmio(dev, base,
> +	regmap = devm_regmap_init_mmio(dev, base,
>  					&syscon_regmap_config);
> -	if (IS_ERR(syscon->regmap)) {
> +	if (IS_ERR(regmap)) {
>  		dev_err(dev, "regmap init failed\n");
> -		return PTR_ERR(syscon->regmap);
> +		return PTR_ERR(regmap);
>  	}
> 
> -	platform_set_drvdata(pdev, syscon);
> +	ret = of_syscon_register(dev->of_node, regmap);
> +	if (ret)
> +		return ret;
> 
>  	dev_dbg(dev, "regmap %pR registered\n", res);
> 
> diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h index
> 75e543b..dc2807b 100644
> --- a/include/linux/mfd/syscon.h
> +++ b/include/linux/mfd/syscon.h
> @@ -18,8 +18,12 @@
>  #include <linux/err.h>
> 
>  struct device_node;
> +struct regmap;
> 
>  #ifdef CONFIG_MFD_SYSCON
> +extern int of_syscon_register(struct device_node *np, struct regmap
> +*regmap); extern void of_syscon_unregister(struct device_node *np);
> +
>  extern struct regmap *syscon_node_to_regmap(struct device_node *np);
extern
> struct regmap *syscon_regmap_lookup_by_compatible(const char *s);  extern
struct
> regmap *syscon_regmap_lookup_by_pdevname(const char *s); @@ -27,6 +31,16
> @@ extern struct regmap *syscon_regmap_lookup_by_phandle(
>  					struct device_node *np,
>  					const char *property);
>  #else
> +static inline int of_syscon_register(struct device_node *np,
> +				       struct regmap *regmap)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline void of_syscon_unregister(struct device_node *np) { }
> +
>  static inline struct regmap *syscon_node_to_regmap(struct device_node
*np)  {
>  	return ERR_PTR(-ENOSYS);
> --
> 1.7.9.5

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