[PATCH] i2c: Add support for device-tree based chip initialization

[Guenter Roeck]

Some I2C devices are not or not correctly initialized by the firmware.
Configuration would be possible via platform data, but that would require
per-driver platform data and a lot of code, and changing it would not be
possible without re-compiling the kernel. It is more elegant to do it
generically via devicetree properties.

Add a generic I2C devicetree property named "reg-init". This property provides
a sequence of device initialization commands to be executed prior to calling
the probe function for a given device.

Signed-off-by: Guenter Roeck <linux at roeck-us.net>
---
 .../devicetree/bindings/i2c/trivial-devices.txt    |   24 +++++++
 drivers/i2c/i2c-core.c                             |   68 ++++++++++++++++++++
 2 files changed, 92 insertions(+)

diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
index 2f5322b..33b694e 100644
--- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt
+++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
@@ -2,6 +2,30 @@ This is a list of trivial i2c devices that have simple device tree
 bindings, consisting only of a compatible field, an address and
 possibly an interrupt line.
 
+Device initialization is supported with an optional reg-init property.
+This property contains a sequence of commands to be written into the chip.
+Each command consists of four values: Register, command type, mask, and data.
+	Register:
+		Register or command address
+	Command type:
+		0: SMBus write byte
+		1: SMBus write byte data
+		2: SMBus write word data
+	Mask:
+		If set, the register is read and masked with this value.
+	Data:
+		Data to be written (or with original data and mask if set)
+
+Example:
+	max6696 at 1a {
+		compatible = "maxim,max6696";
+		reg = <0x1a>;
+		reg-init = <
+			0x09 1 0x00 0x24
+			0x21 1 0x00 0x05
+		>;
+	};
+
 If a device needs more specific bindings, such as properties to
 describe some aspect of it, there needs to be a specific binding
 document for it just like any other devices.
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index a7edf98..49f8b74 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -104,6 +104,69 @@ static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env)
 #define i2c_device_uevent	NULL
 #endif	/* CONFIG_HOTPLUG */
 
+static int i2c_dev_of_init(struct i2c_client *client, struct device *dev)
+{
+	const u32 *reg_init;
+	int rlen;
+	int val;
+	u32 reg, access, mask, data;
+
+	reg_init = of_get_property(dev->of_node, "reg-init", &rlen);
+	if (!reg_init)
+		return 0;
+
+	if (!rlen || rlen % 4)
+		return -EINVAL;
+
+	while (rlen >= 4) {
+		reg = reg_init[0];
+		access = reg_init[1];
+		mask = reg_init[2];
+		data = reg_init[3];
+
+		if (reg > 0xff)
+			return -EINVAL;
+
+		switch (access) {
+		default:
+			return -EINVAL;
+		case 0:
+			val = 0;
+			break;
+		case 1:
+			val = mask ? i2c_smbus_read_byte_data(client, reg) : 0;
+			break;
+		case 2:
+			val = mask ? i2c_smbus_read_word_data(client, reg) : 0;
+			break;
+		}
+		if (val < 0)
+			return val;
+
+		val &= mask;
+		val |= data;
+
+		switch (access) {
+		default:
+		case 0:
+			val = i2c_smbus_write_byte(client, reg);
+			break;
+		case 1:
+			val = i2c_smbus_write_byte_data(client, reg, val);
+			break;
+		case 2:
+			val = i2c_smbus_write_word_data(client, reg, val);
+			break;
+		}
+		if (val < 0)
+			return val;
+
+		reg_init += 4;
+		rlen -= 4 * sizeof(u32);
+	}
+	return 0;
+}
+
 static int i2c_device_probe(struct device *dev)
 {
 	struct i2c_client	*client = i2c_verify_client(dev);
@@ -122,7 +185,12 @@ static int i2c_device_probe(struct device *dev)
 					client->flags & I2C_CLIENT_WAKE);
 	dev_dbg(dev, "probe\n");
 
+	status = i2c_dev_of_init(client, dev);
+	if (status)
+		goto error;
+
 	status = driver->probe(client, i2c_match_id(driver->id_table, client));
+error:
 	if (status) {
 		client->driver = NULL;
 		i2c_set_clientdata(client, NULL);
-- 
1.7.9.7