linux-kernel - [PATCH v2 2/2] i2c: muxes: pca954x: Enable features on MAX7357/MAX7358

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Date:   Thu, 31 Aug 2023 12:15:12 +0200
From:   Naresh Solanki <naresh.solanki@...ements.com>
To:     Peter Rosin <peda@...ntia.se>
Cc:     Patrick Rudolph <patrick.rudolph@...ements.com>,
        Naresh Solanki <Naresh.Solanki@...ements.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] i2c: muxes: pca954x: Enable features on MAX7357/MAX7358

From: Patrick Rudolph <patrick.rudolph@...ements.com>

Detect that max7357 is being used and run custom init sequence.
Enable additional features based on DT settings and unconditionally
release the shared interrupt pin after 1.6 seconds and allow to use
it as reset.

The init sequence is not run for max7358 that needs to be unlocked
first, but that would need the unimplemented function
i2c_probe_func_quick_write().

Signed-off-by: Patrick Rudolph <patrick.rudolph@...ements.com>
Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
---
Changes in V2:
- Update comments
- Update check for DT properties
---
 drivers/i2c/muxes/i2c-mux-pca954x.c | 62 +++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 2219062104fb..e4bf72122c9f 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -57,6 +57,23 @@
 
 #define PCA954X_IRQ_OFFSET 4
 
+/*
+ * MAX7357's configuration register is writeable after POR, but
+ * can be locked by setting the basic mode bit. MAX7358 configuration
+ * register is locked by default and needs to be unlocked first.
+ * 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 +494,43 @@ 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)) {
+		dev_warn(&client->dev, "Device not configured: SMBUS_WRITE_BYTE_DATA is unsupported\n");
+		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 signal is shared with the reset pin. Release the
+	 * interrupt after 1.6 seconds to allow using the pin as reset.
+	 * The interrupt isn't serviced yet.
+	 */
+	conf |= MAX7357_CONF_RELEASE_INT;
+
+	if (device_property_read_bool(&client->dev, "maxim,isolate-stuck-channel"))
+		conf |= MAX7357_CONF_DISCON_SINGLE_CHAN;
+	if (device_property_read_bool(&client->dev, "maxim,send-flush-out-sequence"))
+		conf |= MAX7357_CONF_FLUSH_OUT;
+	if (device_property_read_bool(&client->dev, "maxim,preconnection-wiggle-test-enable"))
+		conf |= MAX7357_CONF_PRECONNECT_TEST;
+
+	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
  */
@@ -485,6 +539,7 @@ static int pca954x_probe(struct i2c_client *client)
 	const struct i2c_device_id *id = i2c_client_get_device_id(client);
 	struct i2c_adapter *adap = client->adapter;
 	struct device *dev = &client->dev;
+	struct device_node *node = dev->of_node;
 	struct gpio_desc *gpio;
 	struct i2c_mux_core *muxc;
 	struct pca954x *data;
@@ -560,6 +615,13 @@ static int pca954x_probe(struct i2c_client *client)
 	 * initializes the mux to a channel
 	 * or disconnected state.
 	 */
+	if ((node && of_device_is_compatible(node, "maxim,max7357")) ||
+	    id->driver_data == max_7357)
+		ret = max7357_init(client, data);
+	else if ((node && of_device_is_compatible(node, "maxim,max7358")) ||
+		 id->driver_data == max_7358)
+		dev_warn(dev, "Device not configured: unlock sequence not implemented\n");
+
 	ret = pca954x_init(client, data);
 	if (ret < 0) {
 		dev_warn(dev, "probe failed\n");
-- 
2.41.0