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serial: max310x: honour rs485 properties from per-channel DT subnode

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The MAX310x DT binding pulls in /schemas/serial/rs485.yaml via its allOf
list, advertising the rs485-* properties defined there - none of which
were honoured at runtime, because the driver never called
uart_get_rs485_mode().

All channels share the parent SPI/I2C device, so uart_get_rs485_mode()
called directly on each port would read the same chip-level fwnode for
every call. Walk dev->of_node's children for the "serial@N" subnode
with matching reg, and temporarily retarget the parent device's fwnode
while uart_get_rs485_mode() runs, so each channel picks up its own
subnode's properties. Probe is serialised, so the swap is safe.

For single-channel variants (max3107, max3108), fall back to the chip's
own fwnode when no subnode is present, so existing DTs that declare
rs485 properties at the top level keep working.

Signed-off-by: Tapio Reijonen <tapio.reijonen@vaisala.com>
Link: https://patch.msgid.link/20260615-b4-max310x-rs485-dt-v3-3-7e79f064bdd7@vaisala.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tapio Reijonen
2026-06-15 10:27:37 +00:00
committed by Greg Kroah-Hartman
parent f3fd73bf20
commit bed094602f
1 changed files with 37 additions and 0 deletions
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37
drivers/tty/serial/max310x.c
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@@ -1452,6 +1452,9 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty
#endif
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);
@@ -1461,6 +1464,40 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty
}
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) {
u32 reg;
if (!of_node_name_eq(child, "serial"))
continue;
if (of_property_read_u32(child, "reg", &reg))
continue;
if (reg == i) {
port_np = child;
break;
}
}
/*
* Temporarily retarget dev's fwnode to the per-port subnode
* so uart_get_rs485_mode() picks up the per-port properties.
* For single-port variants, fall back to the chip's own
* fwnode so legacy DTs that declare rs485 properties at the
* top level keep working.
*/
if (port_np) {
device_set_node(dev, of_fwnode_handle(port_np));
ret = uart_get_rs485_mode(&s->p[i].port);
device_set_node(dev, saved_fwnode);
of_node_put(port_np);
if (ret)
goto out_uart;
} else if (devtype->nr == 1) {
ret = uart_get_rs485_mode(&s->p[i].port);
if (ret)
goto out_uart;
}
/* Register port */
ret = uart_add_one_port(&max310x_uart, &s->p[i].port);
if (ret)