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Increasing CPU speed
Added by Stéphane Peter almost 12 years ago
Hello,
As mentioned in the title, we plan to increase the cpu speed from 300MHz (default) to 456MHz. In a Linux environment this isn't a problem because the command
echo 456000> /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeedhandles everything from adjusting the PLL control register and increasing the core voltage to 1.3V from the PMIC.
But what is in a pure SysBios environment (ARM+DSP running SysBios)?
Can you explain what and how we have to do for achieving the same functionality in SysBios.
Stéphane
Replies (2)
RE: Increasing CPU speed - Added by Michael Williamson almost 12 years ago
You have both the ARM+DSP running sysbios? Which do you intend to control the CPU speed (they are tied to the same clock)? I am assuming the ARM?
If you have reference code for the TI OMAP-L138 EVM: the key difference you'll need to account for is the TI-EVM and the MityDSP-L138F SOMs use different PMIC's. The I2C command most be converted to set DCDC1 of the on-board TPS65023 to 1.3 volts prior to adjusting the PLLs, you'll need to update TI's reference code in this area to use the MityDSP-L138F.
After you update the DCDC1, you should be able to update the PLL0 and the resulting SYSCLK dividers to your application's needs. I don't know what peripherals you need and the specifics of your application, you'll need to reference the OMAP-L138 TRM for configuring the PLL and the dividers (and the peripheral device dividers, if appropriate).
You really can't alter PLL1 unless you roll your own UBL, as it will impact the mDDR clocking. If you need to do this, you will need to watch the mobile DDR configuration remains <= 150 MHz. It might be best to check out the UBL code for specifics of the PLL1 and EMIF setup, located for the MityDSP in MDK_20XX-XX-XX/sw/3rdparty/OMAP-L138_FlashAndBootUtils_2_27/OMAP-L138/Common/src/device.c.
Not sure if this is helpful or not.
-Mike
RE: Increasing CPU speed - Added by Stéphane Peter almost 12 years ago
Hello Mike,
Some parts of your answer were really helpful and gave me some hints such as I think I can proceed.
My hope was, that you could help me with a code snipped (or link) how you implemented the core voltage improvement, because I couldn't find that part in the Linux sources. - But with the datasheet of the TPS65023 it should also be possible to find a solution...
You were right twice:- Yes, we intend to let the ARM be the clock master.
- How we have to configure the PLL and the dividers strongly relates to our system setup.
Thanks
Stéphane
