Hi,
the UART instances are configurated in the device tree.
For example on ST board, a second uart instance (usart3) is present on extension connector but deactivated by default....
this UART can be used in U-Boot just by enable the already existing node in boar device tree:
&usart3 {
status = "okay";
};
serial_getc()/serial_putc() = it is API to manage the serial console, i.e the current selected device
(gd->cur_serial_dev)
For direct access to other serial device, you shoul use directly the serial UCLASS ops.
A example of usage can be found in /arch/arm/mach-stm32mp/cmd_stm32prog/stm32prog_serial.c,
something like :
if (uclass_get_device_by_seq(UCLASS_SERIAL, instance, &dev)) {
log_err("serial %d device not found\n", instance);
return -ENODEV;
}
ops = serial_get_ops(dev);
ops->setconfig(dev, serial_config);
......
err = ops->getc(down_serial_dev);
err = ops->putc(down_serial_dev, w_byte);
see U-Class for ops complete API description in include/serial.h
/**
* struct struct dm_serial_ops - Driver model serial operations
*
* The uclass interface is implemented by all serial devices which use
* driver model.
*/
struct dm_serial_ops {
...
Regards
Patrick
