[PATCH v3] mfd: syscon: Support early initialization

[Michal Simek]

Some platforms need to get system controller
ready as soon as possible.
The patch provides early_syscon_initialization
which create early mapping for all syscon compatible
devices in early_syscon_probe.
Regmap is get via syscon_early_regmap_lookup_by_phandle()

Regular device probes attach device to regmap
via regmap_attach_dev().

For early syscon initialization is necessary to extend
struct syscon and provide remove function
which unmap all early init structures.

Signed-off-by: Michal Simek <michal.simek@xxxxxxxxxx>
---

Changes in v3:
- Keep backward compatibility for platform drivers and test it
- Use only one probe method which is early_syscon_probe
  suggested by Lee Jones. Do not force anybody to call early_syscon_init
- Add kernel-doc description

Changes in v2:
- Fix bad logic in early_syscon_probe
- Fix compilation failure for x86_64 reported by zero day testing system
- Regmap change available here
  git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap.git tags/nodev

 drivers/mfd/syscon.c       | 159 ++++++++++++++++++++++++++++++++++++++++-----
 include/linux/mfd/syscon.h |  11 ++++
 2 files changed, 153 insertions(+), 17 deletions(-)

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 71841f9..8e2ff88 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -20,12 +20,15 @@
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
+#include <linux/slab.h>
 #include <linux/mfd/syscon.h>

 static struct platform_driver syscon_driver;

 struct syscon {
+	void __iomem *base;
 	struct regmap *regmap;
+	struct resource res;
 };

 static int syscon_match_node(struct device *dev, void *data)
@@ -95,6 +98,30 @@ struct regmap *syscon_regmap_lookup_by_pdevname(const char *s)
 }
 EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_pdevname);

+/**
+ * syscon_early_regmap_lookup_by_phandle - Early phandle lookup function
+ * @np:		device_node pointer
+ * @property:	property name which handle system controller phandle
+ * Return:	regmap pointer, an error pointer otherwise
+ */
+struct regmap *syscon_early_regmap_lookup_by_phandle(struct device_node *np,
+						     const char *property)
+{
+	struct device_node *syscon_np;
+	struct syscon *syscon;
+
+	syscon_np = of_parse_phandle(np, property, 0);
+	if (!syscon_np)
+		return ERR_PTR(-ENODEV);
+
+	syscon = syscon_np->data;
+
+	of_node_put(syscon_np);
+
+	return syscon->regmap;
+}
+EXPORT_SYMBOL_GPL(syscon_early_regmap_lookup_by_phandle);
+
 struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
 					const char *property)
 {
@@ -123,36 +150,118 @@ static struct regmap_config syscon_regmap_config = {
 	.reg_stride = 4,
 };

-static int syscon_probe(struct platform_device *pdev)
+/**
+ * early_syscon_probe - Early system controller probe method
+ * @np:		device_node pointer
+ * @syscon_p:	syscon pointer
+ * @res:	device IO resource
+ * Return:	0 if successful, a negative error code otherwise
+ */
+static int early_syscon_probe(struct device_node *np, struct syscon **syscon_p,
+			      struct resource *res)
 {
-	struct device *dev = &pdev->dev;
 	struct syscon *syscon;
-	struct resource *res;
-	void __iomem *base;
+	int ret;
+
+	if (np && np->data) {
+		pr_debug("Early syscon was called\n");
+		*syscon_p = (struct syscon *)&np->data;
+		return 0;
+	}

-	syscon = devm_kzalloc(dev, sizeof(*syscon), GFP_KERNEL);
+	syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
 	if (!syscon)
 		return -ENOMEM;

-	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	if (!res)
-		return -ENOENT;
+	*syscon_p = (struct syscon *)&syscon;

-	base = devm_ioremap(dev, res->start, resource_size(res));
-	if (!base)
-		return -ENOMEM;
+	if (!res && np) {
+		if (of_address_to_resource(np, 0, &syscon->res)) {
+			ret = -EINVAL;
+			goto alloc;
+		}
+
+		np->data = syscon;
+		of_node_put(np);
+	} else {
+		syscon->res = *res;
+	}

-	syscon_regmap_config.max_register = res->end - res->start - 3;
-	syscon->regmap = devm_regmap_init_mmio(dev, base,
-					&syscon_regmap_config);
+	syscon->base = ioremap(syscon->res.start, resource_size(&syscon->res));
+	if (!syscon->base) {
+		pr_err("%s: Unable to map I/O memory\n", __func__);
+		ret = PTR_ERR(syscon->base);
+		goto alloc;
+	}
+
+	syscon_regmap_config.max_register = syscon->res.end -
+					    syscon->res.start - 3;
+	syscon->regmap = regmap_init_mmio(NULL, syscon->base,
+					  &syscon_regmap_config);
 	if (IS_ERR(syscon->regmap)) {
-		dev_err(dev, "regmap init failed\n");
-		return PTR_ERR(syscon->regmap);
+		pr_err("regmap init failed\n");
+		ret = PTR_ERR(syscon->regmap);
+		goto iomap;
 	}
+	if (np)
+		pr_info("syscon: %s regmap %pR registered\n", np->name,
+			&syscon->res);
+
+	return 0;
+
+iomap:
+	iounmap(syscon->base);
+alloc:
+	kfree(syscon);
+
+	return ret;
+}
+
+/**
+ * early_syscon_init - Early system controller initialization
+ */
+void __init early_syscon_init(void)
+{
+	struct device_node *np;
+	struct syscon *syscon = NULL;
+
+	for_each_matching_node_and_match(np, of_syscon_match, NULL) {
+		if (early_syscon_probe(np, &syscon, NULL))
+			BUG();
+	}
+}
+
+/**
+ * syscon_probe - System controller probe method
+ * @pdev:	Platform device
+ * Return:	0 if successful, a negative error code otherwise
+ */
+static int syscon_probe(struct platform_device *pdev)
+{
+	struct syscon *syscon, *syscon_p;
+	struct resource *res = NULL;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = pdev->dev.of_node;
+	int ret;
+
+	if (!np) {
+		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		if (!res)
+			return -ENOENT;
+	}
+	ret = early_syscon_probe(np, &syscon_p, res);
+	if (ret) {
+		dev_err(dev, "Syscon probe failed\n");
+		return ret;
+	}
+
+	syscon = *(struct syscon **)syscon_p;
+
+	regmap_attach_dev(dev, syscon->regmap, &syscon_regmap_config);

 	platform_set_drvdata(pdev, syscon);

-	dev_info(dev, "regmap %pR registered\n", res);
+	dev_info(dev, "regmap attach device to %pR\n", &syscon->res);

 	return 0;
 }
@@ -162,6 +271,21 @@ static const struct platform_device_id syscon_ids[] = {
 	{ }
 };

+/**
+ * syscon_remove - System controller cleanup function
+ * @pdev:	Platform device
+ * Return:	0 always
+ */
+static int syscon_remove(struct platform_device *pdev)
+{
+	struct syscon *syscon = platform_get_drvdata(pdev);
+
+	iounmap(syscon->base);
+	kfree(syscon);
+
+	return 0;
+}
+
 static struct platform_driver syscon_driver = {
 	.driver = {
 		.name = "syscon",
@@ -169,6 +293,7 @@ static struct platform_driver syscon_driver = {
 		.of_match_table = of_syscon_match,
 	},
 	.probe		= syscon_probe,
+	.remove		= syscon_remove,
 	.id_table	= syscon_ids,
 };

diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
index 8789fa3..465c092 100644
--- a/include/linux/mfd/syscon.h
+++ b/include/linux/mfd/syscon.h
@@ -24,6 +24,10 @@ extern struct regmap *syscon_regmap_lookup_by_pdevname(const char *s);
 extern struct regmap *syscon_regmap_lookup_by_phandle(
 					struct device_node *np,
 					const char *property);
+extern struct regmap *syscon_early_regmap_lookup_by_phandle(
+					struct device_node *np,
+					const char *property);
+extern void early_syscon_init(void);
 #else
 static inline struct regmap *syscon_node_to_regmap(struct device_node *np)
 {
@@ -46,6 +50,13 @@ static inline struct regmap *syscon_regmap_lookup_by_phandle(
 {
 	return ERR_PTR(-ENOSYS);
 }
+
+static struct regmap *syscon_early_regmap_lookup_by_phandle(
+					struct device_node *np,
+					const char *property)
+{
+	return ERR_PTR(-ENOSYS);
+}
 #endif

 #endif /* __LINUX_MFD_SYSCON_H__ */
--
1.8.2.3

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