diff mbox

[v4,1/7] mfd: add syscon driver based on regmap

Message ID 1346237818-9498-2-git-send-email-b29396@freescale.com (mailing list archive)
State New, archived
Headers show

Commit Message

Aisheng Dong Aug. 29, 2012, 10:56 a.m. UTC 
From: Dong Aisheng <dong.aisheng@linaro.org>

Add regmap based syscon driver.
This is usually used for access misc bits in registers which does not belong
to a specific module, for example, IMX IOMUXC GPR and ANATOP.
With this driver, client can use generic regmap API to access registers
which are registered into syscon.

Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
---
ChangeLog:
v3->v4:
 * add more description about syscon(provided by Stephen Warren) in binding doc.
 * fix a minor code indent error and remove set cache type code since the cache
   is disabled by default.
v2->v3:
 * export regmap lookup APIs including syscon_node_to_regmap
 * fix a few typo
v1->v2:
 * provide a way of retrieving the regmap, suggested by Mark Brown.
 * delete imx-syscon io accessors and using generic regmap API for client drivers.
 * change to a more generic name for other SoCs to use.
---
 Documentation/devicetree/bindings/mfd/syscon.txt |   20 +++
 drivers/mfd/Kconfig                              |    7 +
 drivers/mfd/Makefile                             |    1 +
 drivers/mfd/syscon.c                             |  170 ++++++++++++++++++++++
 include/linux/mfd/syscon.h                       |   23 +++
 5 files changed, 221 insertions(+), 0 deletions(-)

Comments

Shawn Guo Aug. 31, 2012, 1:26 a.m. UTC | #1 
On Wed, Aug 29, 2012 at 06:56:52PM +0800, Dong Aisheng wrote:
> +config MFD_SYSCON
> +        bool "System Controller Register R/W Based on Regmap"

If the driver only compiles and works for device tree probe, we should
have the following?

	depends on OF

> +        select REGMAP_MMIO
> +        help
> +	  Select this option to enable accessing system control registers
> +	  via regmap.
> +

<snip>

> +struct regmap *syscon_node_to_regmap(struct device_node *np)
> +{
> +	struct syscon *syscon;
> +	struct device *dev;
> +
> +	dev = driver_find_device(&syscon_driver.driver, NULL, np,
> +				 syscon_match);
> +	of_node_put(np);

This looks a little unnatural to me.  Function syscon_node_to_regmap
becomes an API visible to clients, who might never know that np will
be put inside the API.  I'm saying the client may also call of_node_put
to put the node they get.

I think of_node_put should be moved out from here and put into
syscon_node_to_regmap and syscon_regmap_lookup_by_compatible.

Regards,
Shawn

> +
> +	if (!dev)
> +		return ERR_PTR(-EPROBE_DEFER);
> +
> +	syscon = dev_get_drvdata(dev);
> +
> +	return syscon->regmap;
> +}
> +EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
> +
> +struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
> +{
> +	struct device_node *syscon_np;
> +
> +	syscon_np = of_find_compatible_node(NULL, NULL, s);
> +	if (!syscon_np)
> +		return ERR_PTR(-ENODEV);
> +
> +	return syscon_node_to_regmap(syscon_np);
> +}
> +EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
> +
> +struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
> +					const char *property)
> +{
> +	struct device_node *syscon_np;
> +
> +	syscon_np = of_parse_phandle(np, property, 0);
> +	if (!syscon_np)
> +		return ERR_PTR(-ENODEV);
> +
> +	return syscon_node_to_regmap(syscon_np);
> +}
> +EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle);
Aisheng Dong Sept. 3, 2012, 2:31 a.m. UTC | #2 
On Fri, Aug 31, 2012 at 09:26:29AM +0800, Shawn Guo wrote:
> On Wed, Aug 29, 2012 at 06:56:52PM +0800, Dong Aisheng wrote:
> > +config MFD_SYSCON
> > +        bool "System Controller Register R/W Based on Regmap"
> 
> If the driver only compiles and works for device tree probe, we should
> have the following?
> 
> 	depends on OF
> 
Correct.
For currently it only supports dt.

> > +        select REGMAP_MMIO
> > +        help
> > +	  Select this option to enable accessing system control registers
> > +	  via regmap.
> > +
> 
> <snip>
> 
> > +struct regmap *syscon_node_to_regmap(struct device_node *np)
> > +{
> > +	struct syscon *syscon;
> > +	struct device *dev;
> > +
> > +	dev = driver_find_device(&syscon_driver.driver, NULL, np,
> > +				 syscon_match);
> > +	of_node_put(np);
> 
> This looks a little unnatural to me.  Function syscon_node_to_regmap
> becomes an API visible to clients, who might never know that np will
> be put inside the API.  I'm saying the client may also call of_node_put
> to put the node they get.
We probably could add a comment here for the API to avoid this happen.

> 
> I think of_node_put should be moved out from here and put into
> syscon_node_to_regmap and syscon_regmap_lookup_by_compatible.
> 
I guess no, if you want to move of_node_put into syscon_regmap_lookup_by_phandle,
then syscon_regmap_lookup_by_phandle has the same issue.
Actually i had considered your concern when writing this API...
The original purpose of doing like that is saving some duplicated 'of_node_put'
and make the API easy to use.
I searched the kernel dt code and found it existed some similar cases.
e.g: of_irq_find_parent, of_get_next_parent
So it looks to me that it may be usually to do like that for the cases that
the conversion from a node to other thing since the client may only care
about the things converted. For our case, it's regmap.
So i can't think it make too much sense for all client driver have to write
duplicated and meaningless 'of_node_put' code.

Regards
Dong Aisheng

> > +
> > +	if (!dev)
> > +		return ERR_PTR(-EPROBE_DEFER);
> > +
> > +	syscon = dev_get_drvdata(dev);
> > +
> > +	return syscon->regmap;
> > +}
> > +EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
> > +
> > +struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
> > +{
> > +	struct device_node *syscon_np;
> > +
> > +	syscon_np = of_find_compatible_node(NULL, NULL, s);
> > +	if (!syscon_np)
> > +		return ERR_PTR(-ENODEV);
> > +
> > +	return syscon_node_to_regmap(syscon_np);
> > +}
> > +EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
> > +
> > +struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
> > +					const char *property)
> > +{
> > +	struct device_node *syscon_np;
> > +
> > +	syscon_np = of_parse_phandle(np, property, 0);
> > +	if (!syscon_np)
> > +		return ERR_PTR(-ENODEV);
> > +
> > +	return syscon_node_to_regmap(syscon_np);
> > +}
> > +EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle);
Shawn Guo Sept. 3, 2012, 3:09 a.m. UTC | #3 
On Mon, Sep 03, 2012 at 10:31:03AM +0800, Dong Aisheng wrote:
> > 
> > I think of_node_put should be moved out from here and put into
> > syscon_node_to_regmap and syscon_regmap_lookup_by_compatible.
> > 
> I guess no, if you want to move of_node_put into syscon_regmap_lookup_by_phandle,
> then syscon_regmap_lookup_by_phandle has the same issue.

I guess not.  syscon_regmap_lookup_by_phandle itself calls of_parse_phandle,
and that's where the refcount gets incremented, so syscon_regmap_lookup_by_phandle
should be responsible for calling of_node_put to get the refcount decremented.
Aisheng Dong Sept. 3, 2012, 8:02 a.m. UTC | #4 
On Mon, Sep 03, 2012 at 11:09:01AM +0800, Shawn Guo wrote:
> On Mon, Sep 03, 2012 at 10:31:03AM +0800, Dong Aisheng wrote:
> > > 
> > > I think of_node_put should be moved out from here and put into
> > > syscon_node_to_regmap and syscon_regmap_lookup_by_compatible.
> > > 
> > I guess no, if you want to move of_node_put into syscon_regmap_lookup_by_phandle,
> > then syscon_regmap_lookup_by_phandle has the same issue.
> 
> I guess not.  syscon_regmap_lookup_by_phandle itself calls of_parse_phandle,
> and that's where the refcount gets incremented, so syscon_regmap_lookup_by_phandle
> should be responsible for calling of_node_put to get the refcount decremented.
> 
Yes, the of_node_put will be done in syscon_node_to_regmap which is called by
syscon_regmap_lookup_by_phandle,
The reason why we do it is as i said in my last reply.

I think one known issue is that syscon_node_to_regmap may not be suitable to
be used by the driver who still wants to use the regmap node after calling the
syscon_node_to_regmap.
I still do not find such using case but i'm not sure whether it may exist.

Probably the safe way currently to do is just as you said:
Not put the node in syscon_node_to_regmap and let user decide.
Ok, i will update it.

Regards
Dong Aisheng
diff mbox

Patch

diff --git a/Documentation/devicetree/bindings/mfd/syscon.txt b/Documentation/devicetree/bindings/mfd/syscon.txt
new file mode 100644
index 0000000..fe8150b
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/syscon.txt
@@ -0,0 +1,20 @@ 
+* System Controller Registers R/W driver
+
+System controller node represents a register region containing a set
+of miscellaneous registers. The registers are not cohesive enough to
+represent as any specific type of device. The typical use-case is for
+some other node's driver, or platform-specific code, to acquire a
+reference to the syscon node (e.g. by phandle, node path, or search
+using a specific compatible value), interrogate the node (or associated
+OS driver) to determine the location of the registers, and access the
+registers directly.
+
+Required properties:
+- compatible: Should contain "syscon".
+- reg: the register region can be accessed from syscon
+
+Examples:
+gpr: iomuxc-gpr@020e0000 {
+	compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
+	reg = <0x020e0000 0x38>;
+};
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index b1a1462..2b53ed8 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -993,6 +993,13 @@  config MFD_ANATOP
 	  MFD controller. This controller embeds regulator and
 	  thermal devices for Freescale i.MX platforms.
 
+config MFD_SYSCON
+        bool "System Controller Register R/W Based on Regmap"
+        select REGMAP_MMIO
+        help
+	  Select this option to enable accessing system control registers
+	  via regmap.
+
 config MFD_PALMAS
 	bool "Support for the TI Palmas series chips"
 	select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 79dd22d..8384bc9 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -131,4 +131,5 @@  obj-$(CONFIG_MFD_PALMAS)	+= palmas.o
 obj-$(CONFIG_MFD_RC5T583)	+= rc5t583.o rc5t583-irq.o
 obj-$(CONFIG_MFD_SEC_CORE)	+= sec-core.o sec-irq.o
 obj-$(CONFIG_MFD_ANATOP)	+= anatop-mfd.o
+obj-$(CONFIG_MFD_SYSCON)	+= syscon.o
 obj-$(CONFIG_MFD_LM3533)	+= lm3533-core.o lm3533-ctrlbank.o
diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
new file mode 100644
index 0000000..561c2ae
--- /dev/null
+++ b/drivers/mfd/syscon.c
@@ -0,0 +1,170 @@ 
+/*
+ * System Control Driver
+ *
+ * Copyright (C) 2012 Freescale Semiconductor, Inc.
+ * Copyright (C) 2012 Linaro Ltd.
+ *
+ * Author: Dong Aisheng <dong.aisheng@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+static struct platform_driver syscon_driver;
+
+struct syscon {
+	struct device *dev;
+	void __iomem *base;
+	struct regmap *regmap;
+};
+
+static int syscon_match(struct device *dev, void *data)
+{
+	struct syscon *syscon = dev_get_drvdata(dev);
+	struct device_node *dn = data;
+
+	return (syscon->dev->of_node == dn) ? 1 : 0;
+}
+
+struct regmap *syscon_node_to_regmap(struct device_node *np)
+{
+	struct syscon *syscon;
+	struct device *dev;
+
+	dev = driver_find_device(&syscon_driver.driver, NULL, np,
+				 syscon_match);
+	of_node_put(np);
+
+	if (!dev)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	syscon = dev_get_drvdata(dev);
+
+	return syscon->regmap;
+}
+EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
+
+struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
+{
+	struct device_node *syscon_np;
+
+	syscon_np = of_find_compatible_node(NULL, NULL, s);
+	if (!syscon_np)
+		return ERR_PTR(-ENODEV);
+
+	return syscon_node_to_regmap(syscon_np);
+}
+EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
+
+struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
+					const char *property)
+{
+	struct device_node *syscon_np;
+
+	syscon_np = of_parse_phandle(np, property, 0);
+	if (!syscon_np)
+		return ERR_PTR(-ENODEV);
+
+	return syscon_node_to_regmap(syscon_np);
+}
+EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle);
+
+static const struct of_device_id of_syscon_match[] = {
+	{ .compatible = "syscon", },
+	{ },
+};
+
+static struct regmap_config syscon_regmap_config = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+};
+
+static int __devinit syscon_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct syscon *syscon;
+	struct resource res;
+	int ret;
+
+	if (!np)
+		return -ENOENT;
+
+	syscon = devm_kzalloc(&pdev->dev, sizeof(struct syscon),
+			    GFP_KERNEL);
+	if (!syscon)
+		return -ENOMEM;
+
+	syscon->base = of_iomap(np, 0);
+	if (!syscon->base)
+		return -EADDRNOTAVAIL;
+
+	ret = of_address_to_resource(np, 0, &res);
+	if (ret)
+		return ret;
+
+	syscon_regmap_config.max_register = res.end - res.start - 3;
+	syscon->regmap = devm_regmap_init_mmio(&pdev->dev, syscon->base,
+					&syscon_regmap_config);
+	if (IS_ERR(syscon->regmap)) {
+		dev_err(&pdev->dev, "regmap init failed\n");
+		return PTR_ERR(syscon->regmap);
+	}
+
+	syscon->dev = &pdev->dev;
+	platform_set_drvdata(pdev, syscon);
+
+	dev_info(dev, "syscon regmap start 0x%x end 0x%x registered\n",
+		res.start, res.end);
+
+	return 0;
+}
+
+static int __devexit syscon_remove(struct platform_device *pdev)
+{
+	struct syscon *syscon;
+
+	syscon = platform_get_drvdata(pdev);
+	iounmap(syscon->base);
+	platform_set_drvdata(pdev, NULL);
+
+	return 0;
+}
+
+static struct platform_driver syscon_driver = {
+	.driver = {
+		.name = "syscon",
+		.owner = THIS_MODULE,
+		.of_match_table = of_syscon_match,
+	},
+	.probe		= syscon_probe,
+	.remove		= __devexit_p(syscon_remove),
+};
+
+static int __init syscon_init(void)
+{
+	return platform_driver_register(&syscon_driver);
+}
+postcore_initcall(syscon_init);
+
+static void __exit syscon_exit(void)
+{
+	platform_driver_unregister(&syscon_driver);
+}
+module_exit(syscon_exit);
+
+MODULE_AUTHOR("Dong Aisheng <dong.aisheng@linaro.org>");
+MODULE_DESCRIPTION("System Control driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
new file mode 100644
index 0000000..6aeb6b8
--- /dev/null
+++ b/include/linux/mfd/syscon.h
@@ -0,0 +1,23 @@ 
+/*
+ * System Control Driver
+ *
+ * Copyright (C) 2012 Freescale Semiconductor, Inc.
+ * Copyright (C) 2012 Linaro Ltd.
+ *
+ * Author: Dong Aisheng <dong.aisheng@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef __LINUX_MFD_SYSCON_H__
+#define __LINUX_MFD_SYSCON_H__
+
+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_phandle(
+					struct device_node *np,
+					const char *property);
+#endif /* __LINUX_MFD_SYSCON_H__ */