How to set a custom baud rate using 2.6 linux distro on MPC5200 based board?

How to set a custom baud rate using 2.6 linux distro on MPC5200 based board?

[Caruso, Nick]

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I'm trying to set a custom baud rate (500KBaud, in case anyone cares) on one of the PSCs on a MPC5200 board.
The PSC is configured as a serial port and is visible and usable under the 2.6 kernel we're using.

I used to use the following code under 2.4 on an x86 board:

   serial_info.flags = ASYNC_SPD_CUST | ASYNC_LOW_LATENCY;
   serial_info.custom_divisor = 48;  // clock on FTDI chip / 48 == 500KB

   if ( ioctl(tty_fd, TIOCSSERIAL, &serial_info ) < 0) {
     perror("config_serial_port: ioctl TIOCSSERIAL");
     return(-1);
   }

This compiled fine under the ppc cross-dev tools we have but it fails with an "invalid argument" error when run on the ppc board.

I'm busy reading the driver sources but thought someone on the list might be able to help me out.

  thanks!
     --nick caruso
       irobot corporation
       intelligent vehicles
       r-gator project

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Re: How to set a custom baud rate using 2.6 linux distro on MPC5200 based board?

[Eric N. Johnson (ACD)]

>I'm trying to set a custom baud rate (500KBaud, in case anyone cares) on 
>one of the PSCs on a MPC5200 board.
[snip]
>   serial_info.flags = ASYNC_SPD_CUST | ASYNC_LOW_LATENCY;
>    serial_info.custom_divisor = 48;  // clock on FTDI chip / 48 == 500KB
>
>    if ( ioctl(tty_fd, TIOCSSERIAL, &serial_info ) < 0) {
>      perror("config_serial_port: ioctl TIOCSSERIAL");
>      return(-1);
>    }
>
>This compiled fine under the ppc cross-dev tools we have but it fails with 
>an "invalid argument" error when run on the ppc board.

It looks like this code was written for an FTDI serial port.  The FTDI is a 
USB to Serial converter that handles baud rate generation very differently 
from a standard UART.

Eric

RE: How to set a custom baud rate using 2.6 linux distro on MPC5200 based board?

[Caruso, Nick]

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-----Original Message-----
From: linuxppc-embedded-bounces@ozlabs.org on behalf of Eric N. Johnson (ACD)
Sent: Tue 2/15/2005 6:55 PM
To: linuxppc-embedded@ozlabs.org
Subject: Re: How to set a custom baud rate using 2.6 linux distro on MPC5200 based board?
 

>I'm trying to set a custom baud rate (500KBaud, in case anyone cares) on 
>one of the PSCs on a MPC5200 board.
[snip]
>   serial_info.flags = ASYNC_SPD_CUST | ASYNC_LOW_LATENCY;
>    serial_info.custom_divisor = 48;  // clock on FTDI chip / 48 == 500KB
>
>    if ( ioctl(tty_fd, TIOCSSERIAL, &serial_info ) < 0) {
>      perror("config_serial_port: ioctl TIOCSSERIAL");
>      return(-1);
>    }
>
>This compiled fine under the ppc cross-dev tools we have but it fails with 
>an "invalid argument" error when run on the ppc board.

It looks like this code was written for an FTDI serial port.  The FTDI is a 
USB to Serial converter that handles baud rate generation very differently 
from a standard UART.
_______________________________________________

Yes, it was originally written for a USB-to-serial adapter.  However it is my belief that the clock divisor thing works with any serial device, including so-called 16550 devices. 

I think there may be a problem where TIOCSSERIAL doesn't work for the MPC5200 PSC uart code.  It seems that if I get the ports' attributes with TIOCGSERIAL and immediately set the same values on the same port I get an error return from the ioctl call.  I'm talking with our BSP vendor about this.

    best regards, 

      Nick Caruso

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