Issues about DDR Freq

[tony_l_cai]

Hi, all

     I'm so confused about some concepts regarding the freq. One is arm core speed,another is DDR freq. And when I run the DDR stress tool, we will see as follow:

And the MMDC support the max freq is 400MHz, Why can we change the freq to more than 400MHz,such as 672MHz? So the freq here means the Arm core speed?

and when I change the governer we will find its max freq(996MHz), its min freq(396MHz), and I think it is arm core speed, So what is the correlation between the freq in governer and in DDR stress tool? Will the DDR freq change when I change the arm core speed via the governer? If so, how can I get the current speed about the DDR? 3Q~

[Yuri]

  The DDR stress test is non-OS tool to check how robust DRAM interface is,

given current set of parameters (i.e. drive strength settings, timing parameters,

board layout, etc), therefore it implements testing even out of the specified

operation range. The test allows to provide checking for DDR frequencies

from 135 till 672 MHz.

Have a great day,
Yuri

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[tony_l_cai]

Hi，Yuri

     you mean that MMDC can support 400MHz, but we can test the freq from 135MHz to 672MHz? And I need to know whether the DDR freq can change after the governor freq(the ARM core speed freq) changing?

[Yuri]

  The stress tool suppports several devices of i.MX series. Say, the MMDC
of i.MX6Q is specified to work up to 528 MHz. But for testing we can apply

more wide frequency area. As for Linux CPUFREQ feature, it provides

optimal working points regarding core and DDR frequencies, but basically

core and DDR frequencies are independent.

Regards,

Yuri.