Subject: sgiserial.c

From: Gordon McNutt <[email-masked]>
Date: Mon, 09 Oct 2000 14:32:26 -0600

I'm trying to get the Indy's serial port to drive a peripheral card at
115200 baud. It appears to work OK at 9600 baud (the serial port that is
-- the card expects 115200 baud).

First of all, it lookslike the baud_table (in sgiserial.c) used to
convert termios.c_cflag bits to a numeric baud rate was outdated so I
fixed it up. Didn't help. It looks like transmit interrupts are
occurring and the driver is trying to write them to the chip (one byte
per interrupt..? ok, whatever works), but the other end usually isn't
getting anything. When reading, the Indy seems to get bytes but they
don't look good.

BTW, I've tried compiling the kernel without console support on the
serial line but I still get some console messages during boot (at 9600
baud). Haven't  looked too hard at that yet... When I force everybody to
use 115200 baud (via a hack) I don't see the console messages (yes, I
changed minicom to expect 115200 in this case). It just seems like the
chip is not correctly being set to operate at 115200 -- even when
I force it to try.

Has anybody else tried to make the serial port speak 115200?

Thanks,
--Gordon

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From: Marcus Herbert <[email-masked]>
Date: Tue, 10 Oct 2000 05:13:48 +0200

> -- the card expects 115200 baud).

It is limited to 38400 bit/second on hardware side. Read IRIX serial 
manpage:

[..]
SUPPORTED SPEEDS
     The serial ports of all SGI systems support several standard rates
     up through 38400 bps (see termio(7) for these standard rates).
     The serial ports on O2, OCTANE, Origin2000, Onyx2 and Origin200
     systems also support
     
                                31250   57600
                                76800   115200
[..]

This is common knowlegde btw ;-)

-- 
      PGP2 Key-ID: 666/36540865 1997/06/09 <[email-masked]>
       GPG Key-ID: 1024D/2E2DAB44 2000-01-30 <[email-masked]>
        Geek-Code: GCS b O e+ h

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From: Keith Owens <[email-masked]>
Date: Tue, 10 Oct 2000 14:19:17 +1100

On Tue, 10 Oct 2000 05:13:48 +0200, 
>     The serial ports on O2, OCTANE, Origin2000, Onyx2 and Origin200

FWIW, O2's may be rated at 115200 but I can kill my O2 by feeding it
the output from a Linux serial console at 115200.  No diagnostics, just
a solid machine hang.

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From: Ralf Baechle <[email-masked]>
Date: Tue, 10 Oct 2000 05:45:06 +0200

> the output from a Linux serial console at 115200.  No diagnostics, just

The Origin's IOC3 16550 can go even higher rates at low interrupt load
due to it's higher crystal frequency and a NIC-like DMA descriptors.
We just don't do it yet in the Linux driver ...

  Ralf

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From: Alan Cox <[email-masked]>
Date: Tue, 10 Oct 2000 10:41:08 +0100 (BST)

> We just don't do it yet in the Linux driver ...

165x0 chips on x86 running in normal FIFO modes we can do 900Kbits pretty
solidly. You should be able to hit the full 2Mbit without trying