How I could reduce the CPU clock frequency of all T4240 cores?

[gccorraleche]

Hello, this is my first question.

I need to reduce the clock frequency from 1.8ghz to 1.2ghz in all T4240 cores, but I have not clear the way I should take to do that (I2C, OS settings, or buld a new Kernel). The easiest way for me would be using the factory OS/SDK that comes pre-installed.

Thank you, regards. 

[gccorraleche]

Thank you Ufedor for your reply and the references given.

[ufedor]

The frequencies in question can be changed only by modifying RCW fields - refer to the QorIQ T4240 Reference Manual, Figure 4-2. T4240 logic clock subsystem block diagram-cluster group A and Figure 4-3. T4240 logic clock subsystem block diagram-cluster group B.

Pre-built RCW images for T4240RDB could be found in the QorIQ Linux SDK v2.0 PPCE6500 IMAGE ISO available for free at:

https://nxp.flexnetoperations.com/control/frse/download?agree=Accept&element=7726177 

The T4240RDB RCW update procedure is described in the QorIQ SDK 2.0 Documentation, 4.4.17.8 Programming a New U-boot, RCW, FMan Microcode:

https://www.nxp.com/docs/en/supporting-information/QORIQ-SDK-2.0-IC-REV0.pdf

Custom RCW could be prepared using CodeWarrior QorIQ Configuration and Validation Suite PBL Tool:

https://www.nxp.com/docs/en/user-guide/QCVS_PBL_User_Guide.pdf