Serial port initialization broken on Armada 370/XP due to "serial: 8250_dw: Don't use UPF_FIXED_TYPE"

[Gregory CLEMENT <gregory.clement@free-electrons.com>]

Hello,

when I tried to use the linux-next git tree (next-20130226), I
encountered a problem during boot: the serial port was no more
initialized on my Armada XP (ARM SoC) base board . I get:

[...]
Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
sata_mv d00a0000.sata: slots 32 ports 2
[...]
turn off boot console earlycon0


And then nothing.

So after git bisect I ended to the commit " serial: 8250_dw: Don't use
UPF_FIXED_TYPE". Then by adding again the UPF_FIXED_TYPE flag (ie
reverting this commit) I got the usual boot log:

[...]
Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
d0012000.serial: ttyS0 at MMIO 0xd0012000 (irq = 17) is a 8250
console [ttyS0] enabled, bootconsole disabled
console [ttyS0] enabled, bootconsole disabled
d0012100.serial: ttyS1 at MMIO 0xd0012100 (irq = 18) is a 8250
d0012200.serial: ttyS2 at MMIO 0xd0012200 (irq = 29) is a 8250
d0012300.serial: ttyS3 at MMIO 0xd0012300 (irq = 30) is a 8250
sata_mv d00a0000.sata: slots 32 ports 2
[...]
Freeing init memory: 2160K
Starting logging: OK
Initializing random number generator... done.
Starting network...

Welcome to Buildroot
buildroot login:



I understand that the purpose of this commit was to let the driver
find by itself the port type, but I didn't find yet how it managed to
do it and then why it failed in our case.

I will continue to investigate but any pointers are welcome.

Thanks,

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com