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Linux on AT91RM9200

Hello,

I'm designing a system based on ATMEL AT91RM9200 SOC.

The system will run under Linux.

I've couple of quetsion regarding processor initialisation code.

I'm trying to find this code in the linux 2.4 kernel sources and unable to locate it. In particular i'm looking for the code initializing the processor internal PLLs and selecting the master clock source.

Looking in the include/asm-arm/arch-at91rm9200/at91rm9200dk.h

i see following code and comments

#define AT91C_MAIN_CLOCK 179712000 /* from 18.432 MHz crystal (18432000 / 4

  • 39) */ #define AT91C_MASTER_CLOCK 59904000 /* peripheral clock (AT91C_MASTER_CLOCK / 3) */

BTW the second comment id erroneous it should be /* peripheral clock (AT91C_MAIN_CLOCK / 3) */

These 4 and 39 constants are apparently parameters for PLL divider and multiplyer But i'm unable to locate the code where these values are actually programmed into the PLL control registers.

My hardware will be a subset of at91rm9200dk with a twist. I'd like to scrap the 50 MHZ oscilator used to drive RMII REFCLK and istead to connect the at91rm9200 to the 25 Mhz crystal and derive then the 50MHZ from one of the PMC outputs.

Any suggestions or pointers? Thanks Vadim Lebedev CTO

7Chips
Reply to
Vadim Lebedev
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It is not the Linux Kernel's responsibility to do such initialisation - this is done by the bootloader. The Atmel supported version is U-boot - available at sourceforge.

Mhz

Don't do this.

From bitter experience, I can tell you that this won't work. The problem is that a 50MHz clock generated by the PMC is not stable enough for RMII. You will find that Ethernet packets over a certain length (approx 300 bytes) loose synchromisation to the clock and are dropped.

If you want to save the cost of an oscillator, I would suggest using a crystal on your phy and using MII rather than RMII.

Simon

Reply to
Simon Berry

Simon,

Thanks a lot for the advice

Vadim

"Simon Berry" a écrit dans le message de news: snipped-for-privacy@is.co.za...

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Reply to
Vadim Lebedev

Simon,

I've filed to find the the PLL initialisatoin code int the u-boot source....

Can you please point me to the exact file?

Thanks Vadim

"Simon Berry" a écrit dans le message de news: snipped-for-privacy@is.co.za...

to

internal

this

available

is

Reply to
Vadim Lebedev

There is a file "initboot.c". Function is AT91F_InitClocks

Adrian

Reply to
Adrian Bica

Not in the u-boot which is available on sourceforge

Vadim

"Adrian Bica" a écrit dans le message de news: snipped-for-privacy@posting.google.com...

source....

Reply to
Vadim Lebedev

Get the AT91 CD, Das U-Boot there contains what You need.

-- Best Regards Ulf at atmel dot com These comments are intended to be my own opinion and they may, or may not be shared by my employer, Atmel Sweden.

Reply to
Ulf Samuelsson

Check the September 2003 CD-ROM for AT91RM9200DK board.

Reply to
Adrian Bica

...

Ummm.. why is there soemthing on a proprietary CDROM which is not available on the publich CVS server, too?

Did I reject this???

Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88   Web: www.denx.de
I am a computer. I am dumber than any human and smarter than any  ad-
ministrator.
Reply to
Wolfgang Denk

I am not sure, The code is probably in "boot.bin" which is loaded into SRAM at reset. boot.bin will unzip U-boot. I do not know if this is actually considered part of u-boot.

The CD is available free of charge.

-- Best Regards Ulf at atmel dot com These comments are >

Reply to
Ulf Samuelsson

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