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Inconsistencies between iMX6 CCM register description, Clock Root Generator Diagrams, Clock Tree Diagram and the iMX6 SDK

Question asked by Michel Verhagen on Aug 3, 2014
Latest reply on Aug 6, 2014 by Michel Verhagen

There are some inconsistencies between the iMX6(SDL and DQ) Clock Root Generator diagrams,  18.3 CCM Clock Tree, the 18.6 CCM Memory Map/Register Definition, and the iMX6_Platform_SDK.


As an example, take a look at the MLB_SYS_CLK_ROOT diagram (page 812 in the iMX6 SDL RM). The mux in the diagram shows:


0 --> PLL2_PFD2

1 --> DTCP

2 --> PLL2_PFD0

3 --> PLL3


The description for mlb_sys_sel in CBCMR has:


00 derive clock from axi                (this is DTCP)

01 derive clock from pll3

10 307M PFD                              (this is PLL2_PFD0)

11 derive clock from 396M PFD     (this is PLL2_PFD2)


As you can see, the source numbers are different.


The Clock Tree Diagram shows again a different picture with 0 --> PLL3


To make matters even more confusing, the iMX6 SDK calls MLB_SYS_SEL "GPU2D_CLK_SEL", and it has the following selections:


/*! @name Register CCM_CBCMR, field GPU2D_CLK_SEL[17:16] (RW)


* Selector for open vg clock multiplexer


* Values:

* - 00 - derive clock from axi

* - 01 - derive clock from pll3

* - 10 - 307M PFD

* - 11 - derive clock from 396M PFD


Who is right? Up to this point I took the iMX6 SDK as the definitive source of information, but in this case it's very confusing... MLB or GPU2D?


Message was edited by: Michel Verhagen Changed: CMCMR -> CBCMR (fixed typo; there is no CMCMR reg)