Re: [ECOS] Frequency scaling on iPaq

[Cristiano Ligieri Pereira <cpereira at ics dot uci dot edu>]

I want to know if anyone else had the same problem and whether the
solution was as I have just described.

Cristiano.

------------------------------------------------------------
Cristiano Ligieri Pereira - http://www.ics.uci.edu/~cpereira

On Tue, 5 Jun 2001, Nicolas Pitre wrote:

> 
> You are asking questions for which you already found all the answers
> yourself.  What do you want exactly?
> 
> 
> On Mon, 4 Jun 2001, Cristiano Ligieri Pereira wrote:
> 
> >
> > Hi everybody,
> >
> > I'm a little bit confused regarding how to scale the frequency on the
> > StrongARM SA1110 compaq ipaq platform. I'm trying to scale processor
> > frequency simply writting into the appropriate memory mapped register
> > (PPCR - Power Manager PLL Configuration Register). The values to be
> > written and the address of the register are described in the file
> > cyg/hal/hal_sa11x0.h (SA11X0_PWR_MGR_PLL_CONFIG is the register and the
> > values are SA11X0_CLOCK_SPEED_59_0_MHz, SA11X0_CLOCK_SPEED_73_7_MHz,
> > etc...).
> >
> > The default processor operation seems to be at 206.4Mhz. If I try to scale
> > it down to 162.2 it seems to work fine but if I go down one more
> > level, which is 147.5, the system crashes. Looking at the file cpu-scale.c
> > of ipaqlinux source code I noticed that DRAM timing is related to the core
> > clock frequency and then DRAM timing properties have to be adjusted along
> > with the processor core frequency, otherwise DRAM becomes unusable and the
> > kernel crashes (that's is what is described in the source code). Or
> > alternatively the code responsible to scale the frequency has to be
> > executed at the ROM (Flash) memory.
> >
> > Looking at the Intel StrongARM SA-1110 Microprocessor Developer's Manual
> > it is also described that the DRAM timing depends on the processor core
> > frequency.
> >
> > I believe the same thing is happening with eCos/ipaq package since I'm
> > executing the code from the DRAM memory and I'm not adjusting any DRAM
> > timing parameter. Have anyone tried the same thing? Am I saying something
> > wrong? Did anyone have the same problem?
> >
> > Thanks,
> > Cristiano.
> >
> > ------------------------------------------------------------
> > Cristiano Ligieri Pereira - http://www.ics.uci.edu/~cpereira
> >
> >
> 
>