Re: Serial connection is garbled at 32MHz

Hi Greg,

So do I need to maybe change something in my minicom setup?

Alex

On Mon, 07 Apr 2008 10:50:44 +1000
Greg Ungerer <[email protected]> wrote:

> Hi Loren,
> 
> Loren A. Linden Levy wrote:
> > On Fri, 04 Apr 2008 11:06:59 +1000
> > Greg Ungerer <[email protected]> wrote:
> >> Allon Stern wrote:
> >>> On Apr 3, 2008, at 2:20 PM, Loren A. Linden Levy wrote:
> >>>> So I am making progress with this external FPGA (thanks to all the
> >>>> help) and I have the code basically working (I think). One thing we
> >>>> are doing is artificially running the chip (M%282) at 32MHz and this
> >>>> screws up the display over serial (I get nonsense characters). This is
> >>>> not too big a deal b/c I can connect just fine over telnet I was just
> >>>> wondering if there was an obvious way to fix it (settings?). Thanks
> >>>> again.
> >>> I'd suggest looking at (assuming 2.6) linux2.6.x/drivers/serial/mcfserial.c
> >>>
> >>> Look for the line (#636 in my kernel):
> >>> /* compute the baudrate clock */
> >>>
> >>> This is where it determines the baudrate clock based on the CPU clock.
> >>>
> >>> It appears to be based off of MCF_BUSCLK, which is defined in
> >>> linux2.6.x./include/asm-m68knommu/coldfire.h as
> >>> #define      MCF_BUSCLK      (CONFIG_CLOCK_FREQ / CONFIG_CLOCK_DIV)
> >>>
> >>> Both CONFIG_CLOCK_FREQ  and CONFIG_CLOCK_DIV are defined in your .config.
> >> That is right. If you are just feeding a different master
> >> clock to the 5282 then the right change to make is to
> >> CONFIG_CLOCK_FREQ. Look for the config menu item with the
> >> text "Set the core clock frequency". This is only in 2.6.x
> >> kernels.
> >>
> >> If using a 2.4.x kernel then you need to change the clock
> >> frequency manually in the source (look in 
> >> linux-2.4.x/include/asm-arm/coldfire.h).
> > 
> > 
> > It is a 2.4.x kernel and I actually already added the 32MHz option
> > (coldfire.h):
> > 
> > --- linux-2.4.x/include/asm-m68knommu/coldfire.h        25 Sep 2007 06:25:01 -0000      1.19
> > +++ linux-2.4.x/include/asm-m68knommu/coldfire.h        4 Apr 2008 17:46:52 -0000
> > @@ -38,6 +38,7 @@
> >  /*
> >   *     Define master clock frequency.
> >   */
> > +
> >  #if defined(CONFIG_CLOCK_11MHz)
> >  #define        MCF_CLK         11289600
> >  #elif defined(CONFIG_CLOCK_16MHz)
> > @@ -50,6 +51,8 @@
> >  #define        MCF_CLK         25000000
> >  #elif defined(CONFIG_CLOCK_29_5MHz)
> >  #define        MCF_CLK         29500000
> > +#elif defined(CONFIG_CLOCK_32MHz)
> > +#define        MCF_CLK         32000000
> >  #elif defined(CONFIG_CLOCK_33MHz)
> >  #define        MCF_CLK         33000000
> >  #elif defined(CONFIG_CLOCK_40MHz)
> > 
> > 
> > and an entry in the config.in file for kernel configuration.
> > 
> > --- linux-2.4.x/arch/m68knommu/config.in        25 Sep 2007 06:25:01 -0000     1.76
> > +++ linux-2.4.x/arch/m68knommu/config.in        4 Apr 2008 17:46:09 -0000
> > @@ -34,7 +34,6 @@
> >  endmenu
> >  
> >  #############################################################################
> > -
> >  mainmenu_option next_comment
> >  comment 'Processor type and features'
> >  
> > @@ -93,6 +92,7 @@
> >          24MHz  CONFIG_CLOCK_24MHz \
> >          25MHz  CONFIG_CLOCK_25MHz \
> >          29.5MHz CONFIG_CLOCK_29_5MHz \
> > +        32MHz  CONFIG_CLOCK_32MHz \
> >          33MHz  CONFIG_CLOCK_33MHz \
> >          40MHz  CONFIG_CLOCK_40MHz \
> >          45MHz  CONFIG_CLOCK_45MHz \
> > 
> >  
> > Now I am a little confused about the serial baudrate calculation (I
> > found it is actually in the file drivers/char/mcfserial.c).
> > 
> > For the M5282 the calculation is:
> > 
> > #else
> >         baudclk = ((MCF_BUSCLK / mcfrs_baud_table[i]) + 16) / 32;
> > #endif
> > 
> > Which is basically identical to what I found in the manual.  Here the
> > baud_rate table entry is number 14 which is 19200. So the baudclck for
> > 32MHz and 66MHz come out to be 52 and 180 respectively. I guess i do not understand why I am getting junk out if the clock calculation here is being mad correctly. I am in the process of looking throiugh the UART UBG settings to se iff there is something I am missing. Any input or hints would be appreciated.
> 
> Seems like you have taken the correct approach.
> 
> Regards
> Greg
> 
> 
> 
> ------------------------------------------------------------------------
> Greg Ungerer  --  Chief Software Dude       EMAIL:     [email protected]
> Secure Computing Corporation                PHONE:       +61 7 3435 2888
> 825 Stanley St,                             FAX:         +61 7 3891 3630
> Woolloongabba, QLD, 4102, Australia         WEB: http://www.SnapGear.com
> ---
> [email protected]              Send a post to the list.
> [email protected]        Join the list.
> [email protected]    Join the list in digest mode.
> [email protected]     Leave the list.
> 


-- 
 -- 
---------------------------------------------
Loren A. Linden Levy
Department of Physics 
390 UCB 
University of Colorado
Boulder, CO   80309-0390
Tel:   303-735-6146 (CU) / +049 040 8998 4789 (DESY) 
Fax:   303-492-3352 (CU) / +049 040 8998 4034 (DESY) 
Cell:  303-332-2768 (U.S.) / +049 (0)151 5496 1831 (Germany)
Email: [email protected]
url:   http://up.colorado.edu/~lindenle
_____________________________________________
---------------------------------------------
This email has been cryptographically signed.
Search for "lindenle" at pgp.mit.edu
to obtain my public key which can be used 
to verify the authenticity of this message.
_____________________________________________
---------------------------------------------

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)

iD8DBQFH/YzVlZX6YS+3ZksRAta1AJ4oUCBnSQ+EQk/oaWpLjuQMaPBdeACfZCrI
y8W/Aq5KOoYGT10Qt5a4DO0=
=4dAy
-----END PGP SIGNATURE-----