bootcount: add a DM i2c eeprom backing store for bootcount

This driver allows the use of i2c eeprom device or partition as backing
store for boot counter values with DM enabled.

Signed-off-by: Robert Beckett <bob.beckett@collabora.com>

drivers/bootcount/Kconfig

@@ -96,6 +96,16 @@ config DM_BOOTCOUNT_RTC
 	  Accesses to the backing store are performed using the write16
 	  and read16 ops of DM RTC devices.
 
+config DM_BOOTCOUNT_I2C_EEPROM
+	bool "Support i2c eeprom devices as a backing store for bootcount"
+	depends on I2C_EEPROM
+	help
+	  Enabled reading/writing the bootcount in a DM i2c eeprom device.
+	  The wrapper device is to be specified with the compatible string
+	  'u-boot,bootcount-i2c-eeprom' and the 'i2c-eeprom'-property (a phandle
+	  pointing to the underlying i2c eeprom device) and an optional 'offset'
+	  property are supported.
+
 endmenu
 
 endif

drivers/bootcount/Makefile

@@ -10,3 +10,4 @@ obj-$(CONFIG_BOOTCOUNT_EXT)	+= bootcount_ext.o
 
 obj-$(CONFIG_DM_BOOTCOUNT)      += bootcount-uclass.o
 obj-$(CONFIG_DM_BOOTCOUNT_RTC)  += rtc.o
+obj-$(CONFIG_DM_BOOTCOUNT_I2C_EEPROM)	+= i2c-eeprom.o

drivers/bootcount/i2c-eeprom.c

@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2019 Collabora
+ * (C) Copyright 2019 GE
+ */
+
+#include <common.h>
+#include <bootcount.h>
+#include <dm.h>
+#include <i2c_eeprom.h>
+
+static const u8 bootcount_magic = 0xbc;
+
+struct bootcount_i2c_eeprom_priv {
+	struct udevice *i2c_eeprom;
+	u32 offset;
+};
+
+static int bootcount_i2c_eeprom_set(struct udevice *dev, const u32 a)
+{
+	struct bootcount_i2c_eeprom_priv *priv = dev_get_priv(dev);
+	const u16 val = bootcount_magic << 8 | (a & 0xff);
+
+	if (i2c_eeprom_write(priv->i2c_eeprom, priv->offset,
+			     (uint8_t *)&val, 2) < 0) {
+		debug("%s: write failed\n", __func__);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int bootcount_i2c_eeprom_get(struct udevice *dev, u32 *a)
+{
+	struct bootcount_i2c_eeprom_priv *priv = dev_get_priv(dev);
+	u16 val;
+
+	if (i2c_eeprom_read(priv->i2c_eeprom, priv->offset,
+			    (uint8_t *)&val, 2) < 0) {
+		debug("%s: read failed\n", __func__);
+		return -EIO;
+	}
+
+	if (val >> 8 == bootcount_magic) {
+		*a = val & 0xff;
+		return 0;
+	}
+
+	debug("%s: bootcount magic does not match on %04x\n", __func__, val);
+	return -EIO;
+}
+
+static int bootcount_i2c_eeprom_probe(struct udevice *dev)
+{
+	struct ofnode_phandle_args phandle_args;
+	struct bootcount_i2c_eeprom_priv *priv = dev_get_priv(dev);
+	struct udevice *i2c_eeprom;
+
+	if (dev_read_phandle_with_args(dev, "i2c-eeprom", NULL, 0, 0,
+				       &phandle_args)) {
+		debug("%s: i2c-eeprom backing device not specified\n",
+		      dev->name);
+		return -ENOENT;
+	}
+
+	if (uclass_get_device_by_ofnode(UCLASS_I2C_EEPROM, phandle_args.node,
+					&i2c_eeprom)) {
+		debug("%s: could not get backing device\n", dev->name);
+		return -ENODEV;
+	}
+
+	priv->i2c_eeprom = i2c_eeprom;
+	priv->offset = dev_read_u32_default(dev, "offset", 0);
+
+	return 0;
+}
+
+static const struct bootcount_ops bootcount_i2c_eeprom_ops = {
+	.get = bootcount_i2c_eeprom_get,
+	.set = bootcount_i2c_eeprom_set,
+};
+
+static const struct udevice_id bootcount_i2c_eeprom_ids[] = {
+	{ .compatible = "u-boot,bootcount-i2c-eeprom" },
+	{ }
+};
+
+U_BOOT_DRIVER(bootcount_spi_flash) = {
+	.name	= "bootcount-i2c-eeprom",
+	.id	= UCLASS_BOOTCOUNT,
+	.priv_auto_alloc_size = sizeof(struct bootcount_i2c_eeprom_priv),
+	.probe	= bootcount_i2c_eeprom_probe,
+	.of_match = bootcount_i2c_eeprom_ids,
+	.ops	= &bootcount_i2c_eeprom_ops,
+};