See: https://github.com/raspberrypi/linux/issues/3700
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
*/
data->uart.port.uartclk = clk_get_rate(data->clk) * 2;
+ /* The clock is only queried at probe time, which means we get one shot
+ * at this. A zero clock is never going to work and is almost certainly
+ * due to a parent not being ready, so prefer to defer.
+ */
+ if (!data->uart.port.uartclk)
+ return -EPROBE_DEFER;
+
/* register the port */
ret = serial8250_register_8250_port(&data->uart);
if (ret < 0) {