[POWERPC] Enable RTC for Ebony and Walnut (v2)

This patch extends the Ebony and Walnut platform code to instantiate
the existing ds1742 RTC class driver for the DS1743 RTC/NVRAM chip
found on both those boards.  The patch uses a helper function to scan
the device tree and instantiate the appropriate platform_device based
on it, so it should be easy to extend for other boards which have mmio
mapped RTC chips.

Along with this, the device tree binding for the ds1743 chips is
tweaked, based on the existing DS1385 OF binding found at:
	http://playground.sun.com/1275/proposals/Closed/Remanded/Accepted/346-it.txt
Although that document covers the NVRAM portion of the chip, whereas
here we're interested in the RTC portion, so it's not entirely clear
if that's a good model.

This implements only RTC class driver support - that is /dev/rtc0, not
/dev/rtc, and the low-level get/set time callbacks remain
unimplemented.  That means in order to get at the clock you will
either need a modified version of hwclock which will look at
/dev/rtc0, or you'll need to configure udev to symlink rtc0 to rtc.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

arch/powerpc/boot/dts/ebony.dts

@@ -158,9 +158,10 @@
 					};
 				};
 
-				ds1743@1,0 {
+				nvram@1,0 {
 					/* NVRAM & RTC */
-					compatible = "ds1743";
+					compatible = "ds1743-nvram";
+					#bytes = <2000>;
 					reg = <1 0 2000>;
 				};
 

arch/powerpc/boot/dts/walnut.dts

@@ -175,9 +175,10 @@
 				};
 			};
 
-			ds1743@1,0 {
+			nvram@1,0 {
 				/* NVRAM and RTC */
-				compatible = "ds1743";
+				compatible = "ds1743-nvram";
+				#bytes = <2000>;
 				reg = <1 0 2000>;
 			};
 

arch/powerpc/platforms/40x/walnut.c

@@ -36,6 +36,7 @@ static __initdata struct of_device_id walnut_of_bus[] = {
 static int __init walnut_device_probe(void)
 {
 	of_platform_bus_probe(NULL, walnut_of_bus, NULL);
+	of_instantiate_rtc();
 
 	return 0;
 }

arch/powerpc/platforms/44x/Kconfig

@@ -13,6 +13,7 @@ config EBONY
 	default y
 	select 440GP
 	select PCI
+	select OF_RTC
 	help
 	  This option enables support for the IBM PPC440GP evaluation board.
 

arch/powerpc/platforms/44x/ebony.c

@@ -18,6 +18,7 @@
 
 #include <linux/init.h>
 #include <linux/of_platform.h>
+#include <linux/rtc.h>
 
 #include <asm/machdep.h>
 #include <asm/prom.h>
@@ -38,6 +39,7 @@ static __initdata struct of_device_id ebony_of_bus[] = {
 static int __init ebony_device_probe(void)
 {
 	of_platform_bus_probe(NULL, ebony_of_bus, NULL);
+	of_instantiate_rtc();
 
 	return 0;
 }

arch/powerpc/platforms/Kconfig

@@ -321,6 +321,12 @@ config FSL_ULI1575
 config CPM
 	bool
 
+config OF_RTC
+	bool
+	help
+	  Uses information from the OF or flattened device tree to instatiate
+	  platform devices for direct mapped RTC chips like the DS1742 or DS1743.
+
 source "arch/powerpc/sysdev/bestcomm/Kconfig"
 
 endmenu

arch/powerpc/sysdev/Makefile

@@ -28,6 +28,7 @@ obj-$(CONFIG_PPC_I8259)		+= i8259.o
 obj-$(CONFIG_IPIC)		+= ipic.o
 obj-$(CONFIG_4xx)		+= uic.o
 obj-$(CONFIG_XILINX_VIRTEX)	+= xilinx_intc.o
+obj-$(CONFIG_OF_RTC)		+= of_rtc.o
 ifeq ($(CONFIG_PCI),y)
 obj-$(CONFIG_4xx)		+= ppc4xx_pci.o
 endif

arch/powerpc/sysdev/of_rtc.c

@@ -0,0 +1,59 @@
+/*
+ * Instantiate mmio-mapped RTC chips based on device tree information
+ *
+ * Copyright 2007 David Gibson <dwg@au1.ibm.com>, IBM Corporation.
+ *
+ * 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/kernel.h>
+#include <linux/of.h>
+#include <linux/init.h>
+#include <linux/of_platform.h>
+
+static __initdata struct {
+	const char *compatible;
+	char *plat_name;
+} of_rtc_table[] = {
+	{ "ds1743-nvram", "rtc-ds1742" },
+};
+
+void __init of_instantiate_rtc(void)
+{
+	struct device_node *node;
+	int err;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(of_rtc_table); i++) {
+		char *plat_name = of_rtc_table[i].plat_name;
+
+		for_each_compatible_node(node, NULL,
+					 of_rtc_table[i].compatible) {
+			struct resource *res;
+
+			res = kmalloc(sizeof(*res), GFP_KERNEL);
+			if (!res) {
+				printk(KERN_ERR "OF RTC: Out of memory "
+				       "allocating resource structure for %s\n",
+				       node->full_name);
+				continue;
+			}
+
+			err = of_address_to_resource(node, 0, res);
+			if (err) {
+				printk(KERN_ERR "OF RTC: Error "
+				       "translating resources for %s\n",
+				       node->full_name);
+				continue;
+			}
+
+			printk(KERN_INFO "OF_RTC: %s is a %s @ 0x%llx-0x%llx\n",
+			       node->full_name, plat_name,
+			       (unsigned long long)res->start,
+			       (unsigned long long)res->end);
+			platform_device_register_simple(plat_name, -1, res, 1);
+		}
+	}
+}

include/asm-powerpc/of_platform.h

@@ -37,4 +37,6 @@ extern int of_platform_bus_probe(struct device_node *root,
 
 extern struct of_device *of_find_device_by_phandle(phandle ph);
 
+extern void of_instantiate_rtc(void);
+
 #endif	/* _ASM_POWERPC_OF_PLATFORM_H */