usb: typec: tps6598x: Check mode of operation

To prevent loading of the driver when the PD controller is
still in some operational mode that the driver does not
support, checking the mode in driver probe callback
function.

TI PD controllers may be in undefined mode of operation
for example when the application code (firmware) is
completely missing.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tps6598x.c

@@ -14,6 +14,8 @@
 #include <linux/usb/typec.h>
 
 /* Register offsets */
+#define TPS_REG_VID			0x00
+#define TPS_REG_MODE			0x03
 #define TPS_REG_CMD1			0x08
 #define TPS_REG_DATA1			0x09
 #define TPS_REG_INT_EVENT1		0x14
@@ -66,6 +68,20 @@ struct tps6598x_rx_identity_reg {
 #define TPS_TASK_TIMEOUT		1
 #define TPS_TASK_REJECTED		3
 
+enum {
+	TPS_MODE_APP,
+	TPS_MODE_BOOT,
+	TPS_MODE_BIST,
+	TPS_MODE_DISC,
+};
+
+static const char *const modes[] = {
+	[TPS_MODE_APP]	= "APP ",
+	[TPS_MODE_BOOT]	= "BOOT",
+	[TPS_MODE_BIST]	= "BIST",
+	[TPS_MODE_DISC]	= "DISC",
+};
+
 /* Unrecognized commands will be replaced with "!CMD" */
 #define INVALID_CMD(_cmd_)		(_cmd_ == 0x444d4321)
 
@@ -384,6 +400,32 @@ static irqreturn_t tps6598x_interrupt(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+static int tps6598x_check_mode(struct tps6598x *tps)
+{
+	char mode[5] = { };
+	int ret;
+
+	ret = tps6598x_read32(tps, TPS_REG_MODE, (void *)mode);
+	if (ret)
+		return ret;
+
+	switch (match_string(modes, ARRAY_SIZE(modes), mode)) {
+	case TPS_MODE_APP:
+		return 0;
+	case TPS_MODE_BOOT:
+		dev_warn(tps->dev, "dead-battery condition\n");
+		return 0;
+	case TPS_MODE_BIST:
+	case TPS_MODE_DISC:
+	default:
+		dev_err(tps->dev, "controller in unsupported mode \"%s\"\n",
+			mode);
+		break;
+	}
+
+	return -ENODEV;
+}
+
 static const struct regmap_config tps6598x_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
@@ -409,10 +451,8 @@ static int tps6598x_probe(struct i2c_client *client)
 	if (IS_ERR(tps->regmap))
 		return PTR_ERR(tps->regmap);
 
-	ret = tps6598x_read32(tps, 0, &vid);
-	if (ret < 0)
-		return ret;
-	if (!vid)
+	ret = tps6598x_read32(tps, TPS_REG_VID, &vid);
+	if (ret < 0 || !vid)
 		return -ENODEV;
 
 	/*
@@ -425,6 +465,11 @@ static int tps6598x_probe(struct i2c_client *client)
 	if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 		tps->i2c_protocol = true;
 
+	/* Make sure the controller has application firmware running */
+	ret = tps6598x_check_mode(tps);
+	if (ret)
+		return ret;
+
 	ret = tps6598x_read32(tps, TPS_REG_STATUS, &status);
 	if (ret < 0)
 		return ret;