Serial console ports on systems with no console connected.
Quoted 2 lines · Arun Dharankar
Also have the serial port speed set at 115200, I
dont believe this is buffer overrun issue.
If you want to go faster than about than about 38400, you need to get a different clock source for your baud rate generators (Tom Rini has a patch from me to add support for an external clock source for BRGs on the 8260 in linuxppc_2_4_devel). By default, the SCCs and SMCs use a clock source that won't divide cleanly at the higher baud rates - the error becomes so large that it simply stops working - which is what you are getting by the looks of it.
Try running the serial ports at 19200 and see if that works. Cheers!
Murray...
PS: the patch Tom has is trivial - you still need to hack the 8260 uart driver to use the new code (also trivial), plus your hardware needs an external clock source (distinctly non-trivial if your board design doesn't include one already
- our hymod board has a 3686400Hz clock source wired appropriately, which allows up to 230400bps if you use 16x oversampling)
PPS: ppcboot already has support for external BRG clock sources - see include/config_hymod.h for an example of how to configure it. --
Murray Jensen, CSIRO Manufacturing Sci & Tech, Phone: +61 3 9662 7763
Locked Bag No. 9, Preston, Vic, 3072, Australia. Fax: +61 3 9662 7853
Internet: [email protected]
Hymod project: http://www.msa.cmst.csiro.au/projects/Hymod/
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
Quoted 4 lines · Arun Dharankar
As for what I meant to say is that the solution for me is to use the SCC4 based port which has been designated as the console port for the boards. This one does have the flow control wired to the 8260 and makes a difference when I use a null modem.
I dealt with this a long time ago, so the details are a bit hazy, but I seem to recall that you could set the I/O pins on the 8260 that provided the flow control functions to be general purpose I/O pins, which forced the flow control functions to be tied in a default state (which I think was equivalent to the "tied high" state on the serial port side). This way you can use a much simpler serial cable. Check out the I/O pin init table in your board configuration (you also have to ensure that the secondary I/O pins for the flow control functions are not enabled).
Did you try the serial port a lower speeds? Are you running your SCC port at 115200 still? If so, what are you using as the clock source for the BRG for the SCC port? What is your BRG clock rate (it is printed by ppcboot when the board powers up - as brg_clk)?
The default BRG clock is the VCO_OUT clock rate divided by 16. To find out the value of VCO_OUT can be complicated, but on my 8260, which is a 133/133/66 device (cpu/cpm/bus clocks), VCO_OUT is twice the CPM clock rate (266MHz or rather, 266,666,664 Hz give or take a couple). So 266,666,664 / 16 = 16666666Hz We usually use 16 times over-sampling in the SCC, hence you have a number like 1041667 which you must divide to provide all your baud rates. This is not a nice number for baud rates (the Hymod board has an external clock source that is programmed to run at 3686400 which gives the number 230400 after accounting for 16 times oversampling - a nice looking number for baud rates.
I still think you will have trouble with the mismatch in baud rate at speeds higher than 38400 when you use the default BRG_CLK. Can anyone else confirm this? Cheers!
Murray...
--
Murray Jensen, CSIRO Manufacturing & Infra. Tech. Phone: +61 3 9662 7763
Locked Bag No. 9, Preston, Vic, 3072, Australia. Fax: +61 3 9662 7853
Internet: [email protected]
Hymod project: http://www.msa.cmst.csiro.au/projects/Hymod/
To the extent permitted by law, CSIRO does not represent, warrant and/or guarantee that the integrity of this communication has been maintained or that the communication is free of errors, virus, interception or interference.
The information contained in this e-mail may be confidential or privileged. Any unauthorised use or disclosure is prohibited. If you have received this e-mail in error, please delete it immediately and notify Murray Jensen on +61 3 9662 7763. Thank you.
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/