[U-Boot-Users] main clock calculation invalid

[U-Boot-Users] main clock calculation invalid

[Junior]

Hi all,
I'm trying to figure out why the below calculation of my main frequencey clock is not correct.

In the below equation:
maindiv2 = 28
maindiv1 = 13
prediv = 23
ps = 0
and CONFIG_SYS_CLK_FREQ is 14745600.

but I get 93622108 instead of 265420800. How is this possible?

here is the equation which is what get_FCLK returns:

   return (((maindiv2 + 2) * (maindiv1 + 2) * CONFIG_SYS_CLK_FREQ) / 
             ((prediv + 2) * (1 << ps)));

much thanks.
--Jr.

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[U-Boot-Users] main clock calculation invalid

[Wolfgang Denk]

In message <06D6E1270E8.0000028Aejr@inbox.com> you wrote:
>
> I'm trying to figure out why the below calculation of my main frequencey clock is not correct.
> 
> In the below equation:
> maindiv2 = 28
> maindiv1 = 13
> prediv = 23
> ps = 0
> and CONFIG_SYS_CLK_FREQ is 14745600.

I'm sorry, but the user's manual for my Z80 processor does not contain
any part which matches your description.

What might be missing?

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office:  Kirchenstr. 5,       D-82194 Groebenzell,            Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Memories of you remind me of you.                   - Karl Lehenbauer

[U-Boot-Users] main clock calculation invalid

[Junior]

> -----Original Message-----
> From: wd at denx.de
> Sent: Thu, 19 Apr 2007 17:54:59 +0200
> To: ejr at inbox.com
> Subject: Re: [U-Boot-Users] main clock calculation invalid
> 
> In message <06D6E1270E8.0000028Aejr@inbox.com> you wrote:
>> 
>> I'm trying to figure out why the below calculation of my main frequencey
>> clock is not correct.
>> 
>> In the below equation:
>> maindiv2 = 28
>> maindiv1 = 13
>> prediv = 23
>> ps = 0
>> and CONFIG_SYS_CLK_FREQ is 14745600.
> 
> I'm sorry, but the user's manual for my Z80 processor does not contain
> any part which matches your description.
> 
> What might be missing?

I'm not sure what you're missing but my emphasis was on the calculation. 
This is on an ARM9 LH7A404 chip. Now I might be missing something but even on a 16 bit CPU
the calculation result shouldn't change, no?

This is the function, all my printed values are correct before the calculation.

/* return FCLK frequency */
ulong get_FCLK (void)
{
    lh7a40x_csc_t* csc = LH7A404_CSC_PTR;
    ulong maindiv1, maindiv2, prediv, ps;

    /*
     * FCLK = ((MAINDIV1 +2) * (MAINDIV2 +2) * 14.7456MHz) /
     *                   ((PREDIV+2) * (2^PS))
     */
    maindiv2 = (csc->clkset & CLKSET_MAINDIV2) >> 11;
    maindiv1 = (csc->clkset & CLKSET_MAINDIV1) >> 7;
    prediv = (csc->clkset & CLKSET_PREDIV) >> 2;
    ps = (csc->clkset & CLKSET_PS) >> 16;
    printf("maindiv2: %d, maindiv1 %d, prediv %d, ps %d\n",maindiv2,maindiv1,prediv,ps);
    printf("CONFIG_SYS_CLK_FREQ: %d \n",CONFIG_SYS_CLK_FREQ);
    return ( ((maindiv2 + 2) * (maindiv1 + 2) * CONFIG_SYS_CLK_FREQ) / ((prediv + 2) * (1 << ps)));
}

[U-Boot-Users] main clock calculation invalid

[Wolfgang Denk]

In message <0721A2B6C14.000002EAejr@inbox.com> you wrote:
>
> > I'm sorry, but the user's manual for my Z80 processor does not contain
...
> I'm not sure what you're missing but my emphasis was on the calculation. 
> This is on an ARM9 LH7A404 chip. Now I might be missing something but even
> on a 16 bit CPU

You did not understand my little joke about the old Z80 CPU - what  I
wanted  to  pointout  was  that  you completely left out all relevant
information, like which architecture  and  CPU  and  board  you  were
talking about.

> the calculation result shouldn't change, no?

You might have overflows here and there...

> and CONFIG_SYS_CLK_FREQ is 14745600.

It should probably be 14745600L or "UL".

>     ulong maindiv1, maindiv2, prediv, ps;
      ^^^^^
>     printf("maindiv2: %d, maindiv1 %d, prediv %d, ps %d\n",maindiv2,maindiv1,prediv,ps);
                        ^^           ^^         ^^     ^^

%d is for int, not for ulong.

>     printf("CONFIG_SYS_CLK_FREQ: %d \n",CONFIG_SYS_CLK_FREQ);

Same here.

>     return ( ((maindiv2 + 2) * (maindiv1 + 2) * CONFIG_SYS_CLK_FREQ) /
> ((prediv + 2) * (1 << ps)));



Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office:  Kirchenstr. 5,       D-82194 Groebenzell,            Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
What was sliced bread the greatest thing since?

[U-Boot-Users] main clock calculation invalid

[Junior]

> -----Original Message-----
> From: ejr at inbox.com
> Sent: Thu, 19 Apr 2007 08:16:01 -0800
> To: wd at denx.de
> Subject: Re: [U-Boot-Users] main clock calculation invalid
> 
>> -----Original Message-----
>> From: wd at denx.de
>> Sent: Thu, 19 Apr 2007 17:54:59 +0200
>> To: ejr at inbox.com
>> Subject: Re: [U-Boot-Users] main clock calculation invalid
>> 
>> In message <06D6E1270E8.0000028Aejr@inbox.com> you wrote:
>>> 
>>> I'm trying to figure out why the below calculation of my main
>>> frequencey
>>> clock is not correct.
>>> 
>>> In the below equation:
>>> maindiv2 = 28
>>> maindiv1 = 13
>>> prediv = 23
>>> ps = 0
>>> and CONFIG_SYS_CLK_FREQ is 14745600.
>> 
>> I'm sorry, but the user's manual for my Z80 processor does not contain
>> any part which matches your description.
>> 
>> What might be missing?
> 
> I'm not sure what you're missing but my emphasis was on the calculation.
> This is on an ARM9 LH7A404 chip. Now I might be missing something but
> even on a 16 bit CPU
> the calculation result shouldn't change, no?
> 
> This is the function, all my printed values are correct before the
> calculation.
> 
> /* return FCLK frequency */
> ulong get_FCLK (void)
> {
>     lh7a40x_csc_t* csc = LH7A404_CSC_PTR;
>     ulong maindiv1, maindiv2, prediv, ps;
> 
>     /*
>      * FCLK = ((MAINDIV1 +2) * (MAINDIV2 +2) * 14.7456MHz) /
>      *                   ((PREDIV+2) * (2^PS))
>      */
>     maindiv2 = (csc->clkset & CLKSET_MAINDIV2) >> 11;
>     maindiv1 = (csc->clkset & CLKSET_MAINDIV1) >> 7;
>     prediv = (csc->clkset & CLKSET_PREDIV) >> 2;
>     ps = (csc->clkset & CLKSET_PS) >> 16;
>     printf("maindiv2: %d, maindiv1 %d, prediv %d, ps
> %d\n",maindiv2,maindiv1,prediv,ps);
>     printf("CONFIG_SYS_CLK_FREQ: %d \n",CONFIG_SYS_CLK_FREQ);
>     return ( ((maindiv2 + 2) * (maindiv1 + 2) * CONFIG_SYS_CLK_FREQ) /
> ((prediv + 2) * (1 << ps)));
> }
>


I think I see what the problem is but I'm not sure how to fix it in uboot.
When I multiply 450 and 14745600, I get a number greater than 32 bits and the MSB is missed.

I could do an alternative calculation to achive the correct result but unless there is a good trick out
there I'll do that.

Thanks,
--Jr.

[U-Boot-Users] main clock calculation invalid

[Martin Krause]

Hi Junior,

u-boot-users-bounces at lists.sourceforge.net wrote on Thursday, April 19,
2007 8:52 PM: 
> >     return ( ((maindiv2 + 2) * (maindiv1 + 2) *
> > CONFIG_SYS_CLK_FREQ) / ((prediv + 2) * (1 << ps))); }
> > 
> 
> 
> I think I see what the problem is but I'm not sure how to fix it in
> uboot. 
> When I multiply 450 and 14745600, I get a number greater than 32 bits
> and the MSB is missed. 

You could rearrange your formula:

CONFIG_SYS_CLK_FREQ / ((prediv + 2) * (1 << ps)) * (maindiv2 + 2) *
(maindiv1 + 2)

The compiler should do the calculation from left to right.

Regards,
Martin

[U-Boot-Users] main clock calculation invalid

[Wolfgang Denk]

In message <47F3F98010FF784EBEE6526EAAB078D1024F8528@tq-mailsrv.tq-net.de> you wrote:
> 
> You could rearrange your formula:
> 
> CONFIG_SYS_CLK_FREQ / ((prediv + 2) * (1 << ps)) * (maindiv2 + 2) *
> (maindiv1 + 2)
> 
> The compiler should do the calculation from left to right.

And if in doubt, use parens to define the order of evaluation.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office:  Kirchenstr. 5,       D-82194 Groebenzell,            Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
A man either lives life as it happens to him, meets  it  head-on  and
licks it, or he turns his back on it and starts to wither away.
	-- Dr. Boyce, "The Menagerie" ("The Cage"), stardate unknown

[U-Boot-Users] main clock calculation invalid

[Martin Krause]

wd at denx.de wrote on Friday, April 20, 2007 10:18 AM:
> In message
> <47F3F98010FF784EBEE6526EAAB078D1024F8528@tq-mailsrv.tq-net.de> you
> wrote:  
> > 
> > You could rearrange your formula:
> > 
> > CONFIG_SYS_CLK_FREQ / ((prediv + 2) * (1 << ps)) * (maindiv2 + 2) *
> > (maindiv1 + 2) 
> > 
> > The compiler should do the calculation from left to right.
> 
> And if in doubt, use parens to define the order of evaluation.

Ahhh, I always had a strong feeling, that theses parenthesis things 
would be good for something ... ;-)

Ragards,
Martin