The autodetection of IRQ on standard serial ports perhaps made sense on old hardware, but not anymore. These days we know the IRQ from PnP info or simply assume the standard IRQ setting (IRQ4 for 0x3F8, IRQ3 for 0x2F8). The autodetection takes 240 ms of everyone's boot time: autoconfig_irq() probe_irq_off(probe_irq_on()); msleep(20); msleep(100); probe_irq_on(); msleep(20); msleep(100); Just boot with "initcall_debug" to see how long serial8250_init takes. I checked Debian, OpenSuse, Ubuntu, ArchLinux - none of them have this option enabled. --- config-generic | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/config-generic b/config-generic index 7e50163..d179334 100644 --- a/config-generic +++ b/config-generic @@ -2017,7 +2017,7 @@ CONFIG_SERIAL_8250_RUNTIME_UARTS=4 CONFIG_SERIAL_8250_EXTENDED=y CONFIG_SERIAL_8250_MANY_PORTS=y CONFIG_SERIAL_8250_SHARE_IRQ=y -CONFIG_SERIAL_8250_DETECT_IRQ=y +# CONFIG_SERIAL_8250_DETECT_IRQ is not set CONFIG_SERIAL_8250_RSA=y # CONFIG_COMPUTONE is not set CONFIG_CYCLADES=m