Subject: should the kernel be initializing the uarts on the Au1550?

From: Clem Taylor <[email-masked]>
Date: Tue, 26 Apr 2005 15:58:00 -0400

It seems that the kernel (2.6.10) isn't properly initializing the
Au1550 serial ports. All three of the serial ports work, just not at
the same time. Linux seems to need yamon to configure the serial port
first. Out of the box yamon uses UART0 & UART3 and ttyS0 & ttyS2
(UART3, the 1550 doesn't have a UART2) work in linux, but ttyS1
doesn't. If I switch yamon to use UART1 & UART3, then ttyS0 doesn't
seem to work in linux. The serial port that isn't configured by yamon
will hang in an ioctl() on calling tcsetattr().

Before I just cheat and add a third serial port to yamon, should the
kernel be initializing the UARTs or does it really expect the yamon to
initialize them first? Is anyone using all 3 serial ports on an
Au1550?

                                  Thanks,
                                  Clem

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From: Dan Malek <[email-masked]>
Date: Tue, 26 Apr 2005 16:47:43 -0400

On Apr 26, 2005, at 3:58 PM, Clem Taylor wrote:

> Au1550 serial ports.

What do you mean by "initializing"?

> .... Linux seems to need yamon to configure ....

Linux assumes yamon for the Db1xxx and Pb1xxx
boards will configure nearly all of the IO pins
properly.  This is quite the opposite of most embedded
systems that assume nothing and rely on the Linux
board startup functions to do this.

It is just historical, and could be changed.  First, we
need to add sufficient configuration information so
we know what IO is used (serial ports in this case).
Second we need the functions to do the proper
set up based upon the selected configuration.

Then, the discussions (arguments) start about what
should be further assumed about initialization :-)
My preference is that if we should do all of the
initialization and assume nothing, because we could
probably eliminate lots of board specific set up
files and use more common software.

Thanks.

	-- Dan

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From: Pete Popov <[email-masked]>
Date: Tue, 26 Apr 2005 14:53:37 -0700

> initialize them first? Is anyone using all 3 serial ports on an

Yes, it should. And we should really rewrite the serial driver from
scratch. 

Pete