[PATCH 2/2] i2c: muxes: Enable features on MAX7357

[Naresh Solanki <naresh.solanki@9elements.com>]

From: Patrick Rudolph <patrick.rudolph@9elements.com>

Detect that max7357 is being used and run custom init sequence.

By default MAX7357 disconnects all channels on a bus lock-up and
signals	this condition to the bus master using an interrupt.

Disable the interrupt as it's not useful within the kernel and
it might conflict with the reset functionality that shares the same
pin.

Use the introduced 'maxim,bus-lockup-fix' property to enable
faulty channel isolation and flush-out sequence generation.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
---
 drivers/i2c/muxes/i2c-mux-pca954x.c | 56 ++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 2219062104fb..0c1ff1438e7c 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -57,6 +57,21 @@
 
 #define PCA954X_IRQ_OFFSET 4
 
+/*
+ * MAX7357 exposes 7 registers on POR which allow to configure additional
+ * features. The configuration register holds the following settings:
+ */
+#define MAX7357_CONF_INT_ENABLE			BIT(0)
+#define MAX7357_CONF_FLUSH_OUT			BIT(1)
+#define MAX7357_CONF_RELEASE_INT		BIT(2)
+#define MAX7357_CONF_LOCK_UP_CLEAR		BIT(3)
+#define MAX7357_CONF_DISCON_SINGLE_CHAN		BIT(4)
+#define MAX7357_CONF_BUS_LOCKUP_DETECT_DIS	BIT(5)
+#define MAX7357_CONF_ENABLE_BASIC_MODE		BIT(6)
+#define MAX7357_CONF_PRECONNECT_TEST		BIT(7)
+
+#define MAX7357_POR_DEFAULT_CONF		BIT(0)
+
 enum pca_type {
 	max_7356,
 	max_7357,
@@ -477,6 +492,41 @@ static int pca954x_init(struct i2c_client *client, struct pca954x *data)
 	return ret;
 }
 
+static int max7357_init(struct i2c_client *client, struct pca954x *data)
+{
+	struct i2c_adapter *adap = client->adapter;
+	u8 conf = MAX7357_POR_DEFAULT_CONF;
+	int ret;
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
+		return pca954x_init(client, data);
+
+	if (data->idle_state >= 0)
+		data->last_chan = pca954x_regval(data, data->idle_state);
+	else
+		data->last_chan = 0; /* Disconnect multiplexer */
+
+	/*
+	 * The interrupt signals downstream channels that are stuck, but
+	 * there's nothing to do and it prevents using the shared pin as reset.
+	 */
+	conf &= MAX7357_CONF_INT_ENABLE;
+
+	/*
+	 * On bus lock-up isolate the failing channel and try to clear the
+	 * fault by sending the flush-out sequence.
+	 */
+	if (device_property_read_bool(&client->dev, "maxim,bus-lockup-fix"))
+		conf |= MAX7357_CONF_DISCON_SINGLE_CHAN |
+			MAX7357_CONF_FLUSH_OUT;
+
+	ret = i2c_smbus_write_byte_data(client, data->last_chan, conf);
+	if (ret < 0)
+		data->last_chan = 0;
+
+	return ret;
+}
+
 /*
  * I2C init/probing/exit functions
  */
@@ -560,7 +610,11 @@ static int pca954x_probe(struct i2c_client *client)
 	 * initializes the mux to a channel
 	 * or disconnected state.
 	 */
-	ret = pca954x_init(client, data);
+	if ((dev->of_node && of_device_is_compatible(dev->of_node, "maxim,max7357")) ||
+	    id->driver_data == max_7357)
+		ret = max7357_init(client, data);
+	else
+		ret = pca954x_init(client, data);
 	if (ret < 0) {
 		dev_warn(dev, "probe failed\n");
 		ret = -ENODEV;
-- 
2.41.0