ARM: at91: use chipid device for soc detection

So far, the CIDR and EXID registers were in the DBGU interface. This device
has disappeared with the SAMA5D2 family. These registers are exposed
through a new device called chipid.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
[nicolas.ferre@atmel.com: remove useless warnings]
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Rob Herring <robh@kernel.org>
[arnd@arndb.de: suggest to use static functions to reduce scope]
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

Documentation/devicetree/bindings/arm/atmel-at91.txt

@@ -41,6 +41,10 @@ compatible: must be one of:
        - "atmel,sama5d43"
        - "atmel,sama5d44"
 
+Chipid required properties:
+- compatible: Should be "atmel,sama5d2-chipid"
+- reg : Should contain registers location and length
+
 PIT Timer required properties:
 - compatible: Should be "atmel,at91sam9260-pit"
 - reg: Should contain registers location and length

arch/arm/mach-at91/soc.c

@@ -22,48 +22,93 @@
 #include "soc.h"
 
 #define AT91_DBGU_CIDR			0x40
-#define AT91_DBGU_CIDR_VERSION(x)	((x) & 0x1f)
-#define AT91_DBGU_CIDR_EXT		BIT(31)
-#define AT91_DBGU_CIDR_MATCH_MASK	0x7fffffe0
 #define AT91_DBGU_EXID			0x44
+#define AT91_CHIPID_CIDR		0x00
+#define AT91_CHIPID_EXID		0x04
+#define AT91_CIDR_VERSION(x)		((x) & 0x1f)
+#define AT91_CIDR_EXT			BIT(31)
+#define AT91_CIDR_MATCH_MASK		0x7fffffe0
 
-struct soc_device * __init at91_soc_init(const struct at91_soc *socs)
+static int __init at91_get_cidr_exid_from_dbgu(u32 *cidr, u32 *exid)
 {
-	struct soc_device_attribute *soc_dev_attr;
-	const struct at91_soc *soc;
-	struct soc_device *soc_dev;
 	struct device_node *np;
 	void __iomem *regs;
-	u32 cidr, exid;
 
 	np = of_find_compatible_node(NULL, NULL, "atmel,at91rm9200-dbgu");
 	if (!np)
 		np = of_find_compatible_node(NULL, NULL,
 					     "atmel,at91sam9260-dbgu");
-
-	if (!np) {
-		pr_warn("Could not find DBGU node");
-		return NULL;
-	}
+	if (!np)
+		return -ENODEV;
 
 	regs = of_iomap(np, 0);
 	of_node_put(np);
 
 	if (!regs) {
 		pr_warn("Could not map DBGU iomem range");
-		return NULL;
+		return -ENXIO;
 	}
 
-	cidr = readl(regs + AT91_DBGU_CIDR);
-	exid = readl(regs + AT91_DBGU_EXID);
+	*cidr = readl(regs + AT91_DBGU_CIDR);
+	*exid = readl(regs + AT91_DBGU_EXID);
 
 	iounmap(regs);
 
+	return 0;
+}
+
+static int __init at91_get_cidr_exid_from_chipid(u32 *cidr, u32 *exid)
+{
+	struct device_node *np;
+	void __iomem *regs;
+
+	np = of_find_compatible_node(NULL, NULL, "atmel,sama5d2-chipid");
+	if (!np)
+		return -ENODEV;
+
+	regs = of_iomap(np, 0);
+	of_node_put(np);
+
+	if (!regs) {
+		pr_warn("Could not map DBGU iomem range");
+		return -ENXIO;
+	}
+
+	*cidr = readl(regs + AT91_CHIPID_CIDR);
+	*exid = readl(regs + AT91_CHIPID_EXID);
+
+	iounmap(regs);
+
+	return 0;
+}
+
+struct soc_device * __init at91_soc_init(const struct at91_soc *socs)
+{
+	struct soc_device_attribute *soc_dev_attr;
+	const struct at91_soc *soc;
+	struct soc_device *soc_dev;
+	u32 cidr, exid;
+	int ret;
+
+	/*
+	 * With SAMA5D2 and later SoCs, CIDR and EXID registers are no more
+	 * in the dbgu device but in the chipid device whose purpose is only
+	 * to expose these two registers.
+	 */
+	ret = at91_get_cidr_exid_from_dbgu(&cidr, &exid);
+	if (ret)
+		ret = at91_get_cidr_exid_from_chipid(&cidr, &exid);
+	if (ret) {
+		if (ret == -ENODEV)
+			pr_warn("Could not find identification node");
+		return NULL;
+	}
+
 	for (soc = socs; soc->name; soc++) {
-		if (soc->cidr_match != (cidr & AT91_DBGU_CIDR_MATCH_MASK))
+		if (soc->cidr_match != (cidr & AT91_CIDR_MATCH_MASK))
 			continue;
 
-		if (!(cidr & AT91_DBGU_CIDR_EXT) || soc->exid_match == exid)
+		if (!(cidr & AT91_CIDR_EXT) || soc->exid_match == exid)
 			break;
 	}
 
@@ -79,7 +124,7 @@ struct soc_device * __init at91_soc_init(const struct at91_soc *socs)
 	soc_dev_attr->family = soc->family;
 	soc_dev_attr->soc_id = soc->name;
 	soc_dev_attr->revision = kasprintf(GFP_KERNEL, "%X",
-					   AT91_DBGU_CIDR_VERSION(cidr));
+					   AT91_CIDR_VERSION(cidr));
 	soc_dev = soc_device_register(soc_dev_attr);
 	if (IS_ERR(soc_dev)) {
 		kfree(soc_dev_attr->revision);
@@ -91,7 +136,7 @@ struct soc_device * __init at91_soc_init(const struct at91_soc *socs)
 	if (soc->family)
 		pr_info("Detected SoC family: %s\n", soc->family);
 	pr_info("Detected SoC: %s, revision %X\n", soc->name,
-		AT91_DBGU_CIDR_VERSION(cidr));
+		AT91_CIDR_VERSION(cidr));
 
 	return soc_dev;
 }