Re: Bogus serial port ttyS02

[Russell King <rmk@arm.linux.org.uk>]

On Wed, Aug 13, 2003 at 05:40:23PM +0200, Geert Uytterhoeven wrote:
> Linux always finds 3 serial ports instead of 2:
> 
> | ttyS00 at 0x03f8 (irq = 4) is a 16550A
> | ttyS01 at 0x02f8 (irq = 3) is a 16550A
> | ttyS02 at 0x03e8 (irq = 4) is a 16450
> 
> The last one is bogus.

Do you know that it absolutely does not exist?  Can it exist on any
PPC box?  If the answer to both those questions is no, I suggest
you don't probe for it in the first place.

You could enable DEBUG_AUTOCONF in 8250.c in 2.6.0-test3 and give
further probing information. 8)

Looking at PPC's pc_serial.h, it seems that you've told it to probe
there using ASYNC_BOOT_AUTOCONF | ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ.

ASYNC_SKIP_TEST means that we use a reduced test to probe for a port -
we just check that we can read back a value written to 0x3e9.  If this
suceeds, we decide that there is a port present, and go on to try and
derive its type.

If you want to enable the more rigorous tests, remove ASYNC_SKIP_TEST
from the port flags.  This will make us check that the device behaves
like a UART before deciding that it is one.

-- 
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html