Re: Serial connection is garbled at 32MHz

Hi Greg,

Good thought, I went and looked for that too. But alas it was not a
change there other than adding the definition of 32MHz.

Index: asm-m68knommu/coldfire.h
===================================================================
RCS file: /var/cvs/uClinux-2.4.x/include/asm-m68knommu/coldfire.h,v
retrieving revision 1.19
diff -u -r1.19 coldfire.h
--- asm-m68knommu/coldfire.h    25 Sep 2007 06:25:01 -0000      1.19
+++ asm-m68knommu/coldfire.h    17 Apr 2008 15:10:14 -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)


Only CONFIG_M547x, CONFIG_M5208), CONFIG_M5235, CONFIG_M5249, and
CONFIG_M527x get either a multiple of 2 or division by 2.  I am
starting to think it might have something to do with my boot-loader
(u-boot) but I am not sure.

Alex

On Thu, 17 Apr 2008 15:41:13 +1000
Greg Ungerer <[email protected]> wrote:

> 
> Hi Loren,
> 
> Loren A. Linden Levy wrote:
> > So this is really funny if I calculate the UBG1(2) values in this way:
> > 
> > #if defined(CONFIG_CLOCK_32MHz) && defined(CONFIG_M5282)
> >         printk("Alex's baud rate hack!!!\n");
> >         baudclk = ((2*MCF_BUSCLK / mcfrs_baud_table[i]) + 16 ) / 32;
> > 
> > rather than:
> > 
> > #else
> >         baudclk = ((MCF_BUSCLK / mcfrs_baud_table[i]) + 16) / 32;
> > #endif
> > 
> > I get 19200 baud rate. What the heck is going on here....
> 
> Hmmm, you didn't change coldfire.h did you?
> It has conditional code for some ColdFire CPU types that
> divides the master clock frequency by 2 to get that MCF_BUSCLK.
> Though the 5282 is not one of them normally.
> 
> Regards
> Greg
> 
> 
> 
> 
> 
> > 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
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> >>
> > 
> > 
> 
> 


-- 
 -- 
---------------------------------------------
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
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