[PATCH 1/7] serial: max310x: Look up all channels before adding any port

[Tapio Reijonen]

The probe reads each channel's RS485 properties with
uart_get_rs485_mode() and adds the port in the same loop. The GPIO
lookups in uart_get_rs485_mode() can return -EPROBE_DEFER, and for
channel N > 0 that happens after channels 0..N-1 were added, with
their serial_base child devices bound. A probe must not defer after
creating child devices: the bound children re-trigger deferred probing
at once, so the probe runs in a loop for as long as the GPIO provider
is missing, see Documentation/driver-api/driver-model/driver.rst.

Read the properties of all channels first and add the ports in a
second loop. An error in the first loop goes to out_clk: no line is
assigned yet, so out_uart would test line 0 for every channel.

Fixes: bed094602ffb ("serial: max310x: honour rs485 properties from per-channel DT subnode")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tapio Reijonen <tapio.reijonen@xxxxxxxxxxx>
---
 drivers/tty/serial/max310x.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index a0ed70185555eed745d905b36c8b8f162468dd6f..bdfdf4a9000bbd18509746bbfd8ed0ade8164598 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -2010,18 +2010,11 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty
 		goto out_uart;
 #endif
 
+	/* Look up every channel before registering any: lookups may defer */
 	for (i = 0; i < devtype->nr; i++) {
 		struct fwnode_handle *saved_fwnode = dev_fwnode(dev);
 		struct device_node *port_np = NULL;
 		struct device_node *child;
-		unsigned int line;
-
-		line = find_first_zero_bit(max310x_lines, MAX310X_UART_NRMAX);
-		if (line == MAX310X_UART_NRMAX) {
-			ret = -ERANGE;
-			goto out_uart;
-		}
-		s->p[i].port.line = line;
 
 		/* Locate the matching "serial@i" DT subnode, if any. */
 		for_each_available_child_of_node(dev->of_node, child) {
@@ -2050,12 +2043,23 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty
 			device_set_node(dev, saved_fwnode);
 			of_node_put(port_np);
 			if (ret)
-				goto out_uart;
+				goto out_clk;
 		} else if (devtype->nr == 1) {
 			ret = uart_get_rs485_mode(&s->p[i].port);
 			if (ret)
-				goto out_uart;
+				goto out_clk;
 		}
+	}
+
+	for (i = 0; i < devtype->nr; i++) {
+		unsigned int line;
+
+		line = find_first_zero_bit(max310x_lines, MAX310X_UART_NRMAX);
+		if (line == MAX310X_UART_NRMAX) {
+			ret = -ERANGE;
+			goto out_uart;
+		}
+		s->p[i].port.line = line;
 
 		/* Register port */
 		ret = uart_add_one_port(&max310x_uart, &s->p[i].port);

-- 
2.47.3