PLL & clock settings on GTA02: u-boot vs. qi
andy at openmoko.com
Thu Feb 5 12:49:52 CET 2009
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Somebody in the thread at some point said:
| qi seems to start at 400MHz and divides FCLK:HCLK:PCLK into 1:3:6
It's 1:4:8. GTA02 is not stable with external memory at 133MHz MCLK.
| 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
No Qi and U-Boot end with the same 400MHz setup, 50MHz PCLK and 100MHz
However, if Qi feels your battery is really low or absent, it will
instead boot at 200MHz. The intention is that the kernel will do some
stuff that is half-done to defer boot until the battery is happier by
seeing external charging power. But it's problematic, if we try to
stall boot we never get the udc 500mA notification that allows us to
charge. So this is not committed yet.
The second problem is that we don't have any CPUfreq stuff in there yet
to crank us back up to 400MHz.
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