bootcount: add uclass for bootcount

The original bootcount methods do not provide an interface to DM and
rely on a static configuration for I2C devices (e.g. bus, chip-addr,
etc. are configured through defines statically).  On a modern system
that exposes multiple devices in a DTS-configurable way, this is less
than optimal and a interface to DM-based devices will be desirable.

This adds a simple driver that is DM-aware and configurable via DTS.
If ambiguous (i.e. multiple bootcount-devices are present) the
/chosen/u-boot,bootcount-device property can be used to select one
bootcount device.

Initially, this provides support for the following DM devices:
 * RTC devices

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Klaus Goger <klaus.goger@theobroma-systems.com>

drivers/bootcount/Kconfig

@@ -70,6 +70,14 @@ config BOOTCOUNT_AT91
 	bool "Boot counter for Atmel AT91SAM9XE"
 	depends on AT91SAM9XE
 
+config DM_BOOTCOUNT
+        bool "Boot counter in a device-model device"
+	help
+	  Enables reading/writing the bootcount in a device-model based
+	  backing store.  If an entry in /chosen/u-boot,bootcount-device
+	  exists, this will be the preferred bootcount device; otherwise
+	  the first available bootcount device will be used.
+
 endchoice
 
 config BOOTCOUNT_BOOTLIMIT

drivers/bootcount/Makefile

@@ -7,3 +7,5 @@ obj-$(CONFIG_BOOTCOUNT_RAM)	+= bootcount_ram.o
 obj-$(CONFIG_BOOTCOUNT_ENV)	+= bootcount_env.o
 obj-$(CONFIG_BOOTCOUNT_I2C)	+= bootcount_i2c.o
 obj-$(CONFIG_BOOTCOUNT_EXT)	+= bootcount_ext.o
+
+obj-$(CONFIG_DM_BOOTCOUNT)      += bootcount-uclass.o

drivers/bootcount/bootcount-uclass.c

@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2018 Theobroma Systems Design und Consulting GmbH
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <bootcount.h>
+
+int dm_bootcount_get(struct udevice *dev, u32 *bootcount)
+{
+	struct bootcount_ops *ops = bootcount_get_ops(dev);
+
+	assert(ops);
+	if (!ops->get)
+		return -ENOSYS;
+	return ops->get(dev, bootcount);
+}
+
+int dm_bootcount_set(struct udevice *dev, const u32 bootcount)
+{
+	struct bootcount_ops *ops = bootcount_get_ops(dev);
+
+	assert(ops);
+	if (!ops->set)
+		return -ENOSYS;
+	return ops->set(dev, bootcount);
+}
+
+/* Now implement the generic default functions */
+void bootcount_store(ulong val)
+{
+	struct udevice *dev = NULL;
+	ofnode node;
+	const char *propname = "u-boot,bootcount-device";
+	int ret = -ENODEV;
+
+	/*
+	 * If there's a preferred bootcount device selected by the user (by
+	 * setting '/chosen/u-boot,bootcount-device' in the DTS), try to use
+	 * it if available.
+	 */
+	node = ofnode_get_chosen_node(propname);
+	if (ofnode_valid(node))
+		ret = uclass_get_device_by_ofnode(UCLASS_BOOTCOUNT, node, &dev);
+
+	/* If there was no user-selected device, use the first available one */
+	if (ret)
+		ret = uclass_get_device(UCLASS_BOOTCOUNT, 0, &dev);
+
+	if (dev)
+		ret = dm_bootcount_set(dev, val);
+
+	if (ret)
+		pr_debug("%s: failed to store 0x%lx\n", __func__, val);
+}
+
+ulong bootcount_load(void)
+{
+	struct udevice *dev = NULL;
+	ofnode node;
+	const char *propname = "u-boot,bootcount-device";
+	int ret = -ENODEV;
+	u32 val;
+
+	/*
+	 * If there's a preferred bootcount device selected by the user (by
+	 * setting '/chosen/u-boot,bootcount-device' in the DTS), try to use
+	 * it if available.
+	 */
+	node = ofnode_get_chosen_node(propname);
+	if (ofnode_valid(node))
+		ret = uclass_get_device_by_ofnode(UCLASS_BOOTCOUNT, node, &dev);
+
+	/* If there was no user-selected device, use the first available one */
+	if (ret)
+		ret = uclass_get_device(UCLASS_BOOTCOUNT, 0, &dev);
+
+	if (dev)
+		ret = dm_bootcount_get(dev, &val);
+
+	if (ret)
+		pr_debug("%s: failed to load bootcount\n", __func__);
+
+	/* Return the 0, if the call to dm_bootcount_get failed */
+	return ret ? 0 : val;
+}
+
+UCLASS_DRIVER(bootcount) = {
+	.name		= "bootcount",
+	.id		= UCLASS_BOOTCOUNT,
+};