[U-Boot] [PATCH 3/3] bootcount: add DM-based backing store for bootcount

[Philipp Tomsich]

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:
the /chosen/u-boot,bootcount-device property is used to detect the DM
device storing the bootcount and deviceclass-specific commands are
used to read/write the bootcount.

Initially, this provides support for the following DM devices:
 * RTC devices implementing the read8/write8 ops

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

 doc/device-tree-bindings/chosen.txt | 27 +++++++++++
 drivers/bootcount/Kconfig           | 12 +++++
 drivers/bootcount/Makefile          |  1 +
 drivers/bootcount/bootcount_dm.c    | 93 +++++++++++++++++++++++++++++++++++++
 4 files changed, 133 insertions(+)
 create mode 100644 drivers/bootcount/bootcount_dm.c

diff --git a/doc/device-tree-bindings/chosen.txt b/doc/device-tree-bindings/chosen.txt
index da7b4e6..734fd15 100644
--- a/doc/device-tree-bindings/chosen.txt
+++ b/doc/device-tree-bindings/chosen.txt
@@ -42,6 +42,33 @@ Example
 	};
 };
 
+u-boot,bootcount-device property
+--------------------------------
+In a DM-based system, the bootcount may be stored in a device known to
+the DM framework (e.g. in a battery-backed SRAM area within a RTC
+device).  To identify the device to be used for the bootcount, the
+u-boot,bootcount-device property needs to point to the target device.
+
+Further configuration in the target device's node may be required
+(e.g. an offset into an I2C RTC's address space), depending on the
+UCLASS of the target device.
+
+Example
+-------
+/ {
+	chosen {
+	        u-boot,bootcount-device = &rv3029;
+	};
+
+	i2c2 {
+	        rv3029: rtc at 56 {
+		                compatible = "mc,rv3029";
+		                reg = <0x56>;
+				u-boot,bootcount-offset = <0x38>;
+		};
+	};
+};
+
 u-boot,spl-boot-order property
 ------------------------------
 
diff --git a/drivers/bootcount/Kconfig b/drivers/bootcount/Kconfig
index d335ed1..cdde7b5 100644
--- a/drivers/bootcount/Kconfig
+++ b/drivers/bootcount/Kconfig
@@ -70,6 +70,18 @@ config BOOTCOUNT_AT91
 	bool "Boot counter for Atmel AT91SAM9XE"
 	depends on AT91SAM9XE
 
+config BOOTCOUNT_DM
+        bool "Boot counter in a device-model device"
+	help
+	  Enables reading/writing the bootcount in a device-model
+	  device referenced from the /chosen node.  The type of the
+	  device is detected from DM and any additional configuration
+	  information (e.g. the offset into a RTC device that supports
+	  read32/write32) is read from the device's node.
+
+	  At this time the following DM device classes are supported:
+	   * RTC (using read32/write32)
+
 endchoice
 
 config BOOTCOUNT_ALEN
diff --git a/drivers/bootcount/Makefile b/drivers/bootcount/Makefile
index 68bc006..e8ed729 100644
--- a/drivers/bootcount/Makefile
+++ b/drivers/bootcount/Makefile
@@ -7,3 +7,4 @@ 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_BOOTCOUNT_DM)      += bootcount_dm.o
diff --git a/drivers/bootcount/bootcount_dm.c b/drivers/bootcount/bootcount_dm.c
new file mode 100644
index 0000000..99bdb88
--- /dev/null
+++ b/drivers/bootcount/bootcount_dm.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2018 Theobroma Systems Design und Consulting GmbH
+ */
+
+#include <common.h>
+#include <bootcount.h>
+#include <dm.h>
+#include <rtc.h>
+
+const u8 bootcount_magic = 0xbc;
+
+static void bootcount_store_rtc(struct udevice *dev, ulong a)
+{
+#if CONFIG_IS_ENABLED(DM_RTC)
+	u32 offset;
+	const char *offset_propname = "u-boot,bootcount-offset";
+	const u16 val = bootcount_magic << 8 | (a & 0xff);
+
+	if (dev_read_u32(dev, offset_propname, &offset) < 0) {
+		debug("%s: requires %s\n", __func__, offset_propname);
+		return;
+	}
+
+	if (rtc_write16(dev, offset, val) < 0) {
+		debug("%s: rtc_write16 failed\n", __func__);
+		return;
+	}
+#endif
+}
+
+static u32 bootcount_load_rtc(struct udevice *dev)
+{
+#if CONFIG_IS_ENABLED(DM_RTC)
+	u32 offset;
+	const char *offset_propname = "u-boot,bootcount-offset";
+	u16 val;
+
+	if (dev_read_u32(dev, offset_propname, &offset) < 0) {
+		debug("%s: requires %s\n", __func__, offset_propname);
+		goto fail;
+	}
+
+	if (rtc_read16(dev, offset, &val) < 0) {
+		debug("%s: rtc_write16 failed\n", __func__);
+		goto fail;
+	}
+
+	if (val >> 8 == bootcount_magic)
+		return val & 0xff;
+
+	debug("%s: bootcount magic does not match on %04x\n", __func__, val);
+ fail:
+#endif
+	return 0;
+}
+
+/* Now implement the generic default functions */
+void bootcount_store(ulong a)
+{
+	struct udevice *dev;
+	ofnode node;
+	const char *propname = "u-boot,bootcount-device";
+
+	node = ofnode_get_chosen_node(propname);
+	if (!ofnode_valid(node)) {
+		debug("%s: no '%s'\n", __func__, propname);
+		return;
+	}
+
+	/* RTC devices */
+	if (!uclass_get_device_by_ofnode(UCLASS_RTC, node, &dev))
+		return bootcount_store_rtc(dev, a);
+}
+
+ulong bootcount_load(void)
+{
+	struct udevice *dev;
+	ofnode node;
+	const char *propname = "u-boot,bootcount-device";
+
+	node = ofnode_get_chosen_node(propname);
+	if (!ofnode_valid(node)) {
+		debug("%s: no '%s'\n", __func__, propname);
+		return 0;
+	}
+
+	/* RTC devices */
+	if (!uclass_get_device_by_ofnode(UCLASS_RTC, node, &dev))
+		return bootcount_load_rtc(dev);
+
+	return 0;
+}
-- 
2.1.4