PLL & clock settings on GTA02: u-boot vs. qi

scholbert scholbert at
Thu Feb 5 12:38:06 CET 2009

Hi geeks,

i got some questions concerning PLL & Clock initialisation on the GTA02 and
it's actual speed after complete booting.

Yesterday i took a short look into the source code of low-level init
process, and compared both bootloaders used on GTA02. Maybe i should have
stepped a little deeper inside the whole code ;-)
Anyway i realized some differences in initalisation code of PLL and clock
between u-boot and qi.
Please correct me if i'm wrong:
u-boot seems to start at 120MHz and divides FCLK:HCLK:PCLK into 1:2:4 
qi seems to start at 400MHz and divides FCLK:HCLK:PCLK into 1:3:6

As far as i know the basic setting is completely done by the bootloaders,
but afterwards the kernel also may influence these settings.
Assuming that the GTA02 is running at 400MHz while using the device, what
are the actual rates for HCLK and PCLK after booting the kernel?

Does the choosen bootloader affect these settings in the end?
Apart from the more straight forward programming is qi bootloader faster
than u-boot, because of PLL settings?

I'm really interested in these issues and it would be very kind to help me

Best regards,


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