8250 wrong IRQs set after boot

8250 wrong IRQs set after boot

[Toan Pham]

Hi,

I built a linux from scrach distro and setserial is not installed.

At boot up; all of the IRQ numbers for serial ports 1-4 are reported
correctly (according to the bios setting) from the bootup log.  They
are as followed.

ttyS0 at 0x03f8 (irq = 4) is a 16550A
ttyS1 at 0x02f8 (irq = 4) is a 16550A
ttyS2 at 0x03e8 (irq = 11) is a 16550A
ttyS3 at 0x02e8 (irq = 11) is a 16550A


However, after bootup, i login and looked at /proc/tty/driver/serial,
i noticed that all the IRQ for four serial ports

are wrong, and they as as follow:

ttyS0 to IRQ 4
ttyS1 to IRQ 3
ttyS2 to IRQ 4
ttyS3 to IRQ 3


as expected, serial ports ttyS1, ttyS2, and ttyS3 did not function
because the IRQs were reconfigured somehow.  I would like to know what
reconfigured the

IRQs since setserial is not installed in my distro.  I also checked
all the startup scripts in userspace and noticed that nothing would
have reconfigured
these ports.  I am thinking about installing setserial to my distro to
reconfigure the irqs back to the ones listed at bootup; however, I
would like to know

what caused them to change in the first place.


Thank you,


Toan