Re: [PATCH] mfd: syscon: fix syscon probing from dt

[Philipp Zabel <p.zabel@pengutronix.de>]

Am Dienstag, den 06.01.2015, 20:36 +0100 schrieb Arnd Bergmann:
> On Tuesday 06 January 2015 16:30:36 Philipp Zabel wrote:
> > Patch bdb0066df96e ("mfd: syscon: Decouple syscon interface from platform devices")
> > breaks probing pure syscon devices from device tree, such as anatop and
> > iomuxc-gpr on i.MX. This patch adds back the dt id table to match against
> > "syscon" compatible device tree nodes.
> > 
> > Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> > 
> 
> I don't understand it. Why is this required?

The debugfs entries vanished and I'd like to have a device to register
platform device children to. I guess for i.MX iomuxc it could be argued
that the iomuxc-gpr syscon should be merged into the iomuxc pinctrl
device instead of probing iomuxc-gpr as a platform device by itself.
How about allowing to register a syscon for a given device:

----8<----
diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index d2280d6..2633b27 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -42,13 +42,14 @@ static struct regmap_config syscon_regmap_config = {
 	.reg_stride = 4,
 };
 
-static struct syscon *of_syscon_register(struct device_node *np)
+struct syscon *syscon_register(struct device *dev, struct device_node *np)
 {
 	struct syscon *syscon;
 	struct regmap *regmap;
 	void __iomem *base;
 	int ret;
 	struct regmap_config syscon_config = syscon_regmap_config;
+	struct resource res;
 
 	if (!of_device_is_compatible(np, "syscon"))
 		return ERR_PTR(-EINVAL);
@@ -57,7 +58,12 @@ static struct syscon *of_syscon_register(struct device_node *np)
 	if (!syscon)
 		return ERR_PTR(-ENOMEM);
 
-	base = of_iomap(np, 0);
+	if (of_address_to_resource(np, 0, &res)) {
+		ret = -ENOMEM;
+		goto err_map;
+	}
+
+	base = ioremap(res.start, resource_size(&res));
 	if (!base) {
 		ret = -ENOMEM;
 		goto err_map;
@@ -69,7 +75,8 @@ static struct syscon *of_syscon_register(struct device_node *np)
 	 else if (of_property_read_bool(np, "little-endian"))
 		syscon_config.val_format_endian = REGMAP_ENDIAN_LITTLE;
 
-	regmap = regmap_init_mmio(NULL, base, &syscon_config);
+	syscon_regmap_config.max_register = res.end - res.start - 3;
+	regmap = regmap_init_mmio(dev, base, &syscon_config);
 	if (IS_ERR(regmap)) {
 		pr_err("regmap init failed\n");
 		ret = PTR_ERR(regmap);
@@ -91,6 +98,12 @@ err_map:
 	kfree(syscon);
 	return ERR_PTR(ret);
 }
+EXPORT_SYMBOL_GPL(syscon_register);
+
+static struct syscon *of_syscon_register(struct device_node *np)
+{
+	return syscon_register(NULL, np);
+}
 
 struct regmap *syscon_node_to_regmap(struct device_node *np)
 {
diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
index 75e543b..e0c4a86 100644
--- a/include/linux/mfd/syscon.h
+++ b/include/linux/mfd/syscon.h
@@ -17,10 +17,14 @@
 
 #include <linux/err.h>
 
+struct device;
 struct device_node;
+struct syscon;
 
 #ifdef CONFIG_MFD_SYSCON
 extern struct regmap *syscon_node_to_regmap(struct device_node *np);
+extern struct syscon *syscon_register(struct device *dev,
+				      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);
 extern struct regmap *syscon_regmap_lookup_by_phandle(
@@ -32,6 +36,12 @@ static inline struct regmap *syscon_node_to_regmap(struct device_node *np)
 	return ERR_PTR(-ENOSYS);
 }
 
+static struct syscon *syscon_register(struct device *dev,
+				      struct device_node *np)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
 static inline struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
 {
 	return ERR_PTR(-ENOSYS);
--
---->8----

That way the syscon could be registered from iomuxc (pinctrl-imx6q):

----8<----
diff --git a/drivers/pinctrl/freescale/pinctrl-imx6q.c b/drivers/pinctrl/freescale/pinctrl-imx6q.c
index 4d1fcb8..74a68ec 100644
--- a/drivers/pinctrl/freescale/pinctrl-imx6q.c
+++ b/drivers/pinctrl/freescale/pinctrl-imx6q.c
@@ -15,6 +15,7 @@
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/io.h>
+#include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
@@ -473,6 +474,12 @@ static const struct of_device_id imx6q_pinctrl_of_match[] = {
 
 static int imx6q_pinctrl_probe(struct platform_device *pdev)
 {
+	struct device_node *syscon_np;
+
+	syscon_np = of_find_compatible_node(NULL, NULL, "fsl,imx6q-iomuxc-gpr");
+	if (syscon_np)
+		syscon_register(&pdev->dev, syscon_np);
+
 	return imx_pinctrl_probe(pdev, &imx6q_pinctrl_info);
 }
 
---->8----

which makes the regmap debugfs entry return
as /sys/kernel/debug/regmap/20e0000.iomuxc
and allows to register children to the iomuxc-gpr node.

regards
Philipp