wd@denx.de wrote on Friday, October 05, 2007 1:10 PM:
In message 11915787621757-git-send-email-martin.krause@tqs.de you wrote:
On the TQM885D the measurement of cpuclk with the PIT reference timer ist not necessary. Since all module variants use the same
Ummm.. it may not be strictly necessary - but does it hurt? Or is it not working?
To make it work, changes in /cpu/mpc8xx/speed.c would be necessary. I send a patch some weeks ago ("TQM885D: Use the OSCM,feeded by EXTAL = 10 MHz"), which wasn't accepted, because board specific code is not allowed in this file.
external 10 MHz oscillator, the cpuclk only depends on the PLL configuration - which is readable by software.
If it's working as expected, I recommend to leave the measurement as is - it allows for example to easily detect clocking problems for example because of a broken or wrong quartz.
Since we only have one quartz on the TQM885D, we could not do reference measurements like on the other TQM8xx boards (which have two independent external clock sources). So Measuring the clock with the PIT will produce the same result as calculating the clock from the PLL register values.
Another point is, that older TQM885D boards use EXTCLK as clock source and newer versions EXTAL. If the cpuclk is calculated, the same u-boot Image could be used for the older and the newer board versions. If cpuclk is measured two different U-Boot images would be necessary.
Best Regards, Martin Krause