Thread (225 messages) 225 messages, 19 authors, 2015-06-08

[PATCH 01/11] resolve PXA<->8250 serial device address conflict

From: heikki.krogerus@linux.intel.com (Heikki Krogerus)
Date: 2013-12-02 09:49:57
Also in: linux-serial, lkml

Hi,

On Mon, Dec 02, 2013 at 01:23:58PM +0400, Sergei Ianovich wrote:
On Mon, 2013-12-02 at 11:02 +0200, Heikki Krogerus wrote:
quoted
On Sun, Dec 01, 2013 at 10:26:14AM +0400, Sergei Ianovich wrote:
quoted
PXA serial ports have "standard" UART names (ttyS[0-3]), major
device number (4) and first minor device number (64) by default.

If the system has extra 8250 serial port hardware in addition
to onboard PXA serial ports, default settings produce a device
allocation conflict.

The patch provides a configuration option which can move onboard
ports out of the way of 8250_core by assigning a different (204)
major number and corresponding device names (ttySA[0-3]).
<snip>

If drivers/tty/serial/pxa.c was converted to an other probe driver for
the 8250, this would not be an issue.
It seems that my patch is not going to be accepted. However, there is a
device which has both PXA ports and a additional 8250 accent chip. As a
result, there is a device allocation conflict. For the device to be
usable the conflict needs to be resolved.

Do you mean that drivers/tty/serial/pxa.c needs to be rewritten to
support lp8x4x special case?
Sorry I was not clear. I was suggesting that drivers/tty/serial/pxa.c
would be converted to drivers/tty/serial/8250/8250_pxa.c since it
looks to me like just an other 16x50 compatible UART. That would fix
the issue with the name conflict. You would then simply register 8250
ports from two probe drivers (drivers/tty/serial/8250/8250_pxa.c and
drivers/tty/serial/8250/8250_lp8x4x.c).

Depending on the order you register your platform devices (which you
decide in your platform code), but let's say the pxa gets registered
first and let's say it only has one port. You will then have in your
system /dev/ttyS0 for the pxa port and /dev/ttyS[1-4] for the other
UART.

I hope I was able to explain what I mean this time :)

Thanks,

-- 
heikki
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