[PATCH 1/1] mfd: da9063: Support SMBus and I2C mode

[Mark Jonas]

From: Hubert Streidl <hubert.streidl@xxxxxxxxxxxx>

By default the PMIC DA9063 2-wire interface is SMBus compliant. This
means the PMIC will automatically reset the interface when the clock
signal ceases for more than the SMBus timeout of 35 ms.

If the I2C driver / device is not capable of creating atomic I2C
transactions, a context change can cause a ceasing of the the clock
signal. This can happen if for example a real-time thread is scheduled.
Then the DA9063 in SMBus mode will reset the 2-wire interface.
Subsequently a write message could end up in the wrong register. This
could cause unpredictable system behavior.

The DA9063 PMIC also supports an I2C compliant mode for the 2-wire
interface. This mode does not reset the interface when the clock
signal ceases. Thus the problem depicted above does not occur.

This patch makes the I2C mode configurable by device tree. The SMBus
compliant mode is kept as the default.

Signed-off-by: Hubert Streidl <hubert.streidl@xxxxxxxxxxxx>
Signed-off-by: Mark Jonas <mark.jonas@xxxxxxxxxxxx>
---
 Documentation/devicetree/bindings/mfd/da9063.txt |  7 +++++++
 drivers/mfd/da9063-core.c                        |  9 +++++++++
 drivers/mfd/da9063-i2c.c                         | 13 +++++++++++++
 include/linux/mfd/da9063/core.h                  |  1 +
 include/linux/mfd/da9063/registers.h             |  3 +++
 5 files changed, 33 insertions(+)

diff --git a/Documentation/devicetree/bindings/mfd/da9063.txt b/Documentation/devicetree/bindings/mfd/da9063.txt
index 8da879935c59..256f2a25fe0a 100644
--- a/Documentation/devicetree/bindings/mfd/da9063.txt
+++ b/Documentation/devicetree/bindings/mfd/da9063.txt
@@ -19,6 +19,12 @@ Required properties:
 - interrupts : IRQ line information.
 - interrupt-controller
 
+Optional properties:
+
+- i2c-mode : Switch serial 2-wire interface into I2C mode. Without this
+  property the PMIC uses the SMBus mode (resets the interface if the clock
+  ceases for a longer time than the SMBus timeout).
+
 Sub-nodes:
 
 - regulators : This node defines the settings for the LDOs and BUCKs.
@@ -77,6 +83,7 @@ Example:
 		interrupt-parent = <&gpio6>;
 		interrupts = <11 IRQ_TYPE_LEVEL_LOW>;
 		interrupt-controller;
+		i2c-mode;
 
 		rtc {
 			compatible = "dlg,da9063-rtc";
diff --git a/drivers/mfd/da9063-core.c b/drivers/mfd/da9063-core.c
index df407c3afce3..baa1e4310c8c 100644
--- a/drivers/mfd/da9063-core.c
+++ b/drivers/mfd/da9063-core.c
@@ -162,6 +162,15 @@ int da9063_device_init(struct da9063 *da9063, unsigned int irq)
 {
 	int ret;
 
+	if (da9063->i2cmode) {
+		ret = regmap_update_bits(da9063->regmap, DA9063_REG_CONFIG_J,
+				DA9063_TWOWIRE_TO, 0);
+		if (ret < 0) {
+			dev_err(da9063->dev, "Cannot enable I2C mode.\n");
+			return -EIO;
+		}
+	}
+
 	ret = da9063_clear_fault_log(da9063);
 	if (ret < 0)
 		dev_err(da9063->dev, "Cannot clear fault log\n");
diff --git a/drivers/mfd/da9063-i2c.c b/drivers/mfd/da9063-i2c.c
index 3781d0bb7786..af0bf13ab43e 100644
--- a/drivers/mfd/da9063-i2c.c
+++ b/drivers/mfd/da9063-i2c.c
@@ -351,6 +351,17 @@ static const struct of_device_id da9063_dt_ids[] = {
 	{ }
 };
 MODULE_DEVICE_TABLE(of, da9063_dt_ids);
+
+static void da9063_i2c_parse_dt(struct i2c_client *client, struct da9063 *da9063)
+{
+	struct device_node *np = client->dev.of_node;
+
+	if (of_property_read_bool(np, "i2c-mode"))
+		da9063->i2cmode = true;
+	else
+		da9063->i2cmode = false;
+}
+
 static int da9063_i2c_probe(struct i2c_client *i2c,
 			    const struct i2c_device_id *id)
 {
@@ -366,6 +377,8 @@ static int da9063_i2c_probe(struct i2c_client *i2c,
 	da9063->chip_irq = i2c->irq;
 	da9063->type = id->driver_data;
 
+	da9063_i2c_parse_dt(i2c, da9063);
+
 	ret = da9063_get_device_type(i2c, da9063);
 	if (ret)
 		return ret;
diff --git a/include/linux/mfd/da9063/core.h b/include/linux/mfd/da9063/core.h
index fa7a43f02f27..866864c50f78 100644
--- a/include/linux/mfd/da9063/core.h
+++ b/include/linux/mfd/da9063/core.h
@@ -77,6 +77,7 @@ struct da9063 {
 	enum da9063_type type;
 	unsigned char	variant_code;
 	unsigned int	flags;
+	bool	i2cmode;
 
 	/* Control interface */
 	struct regmap	*regmap;
diff --git a/include/linux/mfd/da9063/registers.h b/include/linux/mfd/da9063/registers.h
index 1dbabf1b3cb8..6e0f66a2e727 100644
--- a/include/linux/mfd/da9063/registers.h
+++ b/include/linux/mfd/da9063/registers.h
@@ -1037,6 +1037,9 @@
 #define		DA9063_NONKEY_PIN_AUTODOWN	0x02
 #define		DA9063_NONKEY_PIN_AUTOFLPRT	0x03
 
+/* DA9063_REG_CONFIG_J (addr=0x10F) */
+#define DA9063_TWOWIRE_TO			0x40
+
 /* DA9063_REG_MON_REG_5 (addr=0x116) */
 #define DA9063_MON_A8_IDX_MASK			0x07
 #define		DA9063_MON_A8_IDX_NONE		0x00
-- 
2.25.1