What criteria is frequency range in DDR stress test

[csfttl]

Hi,

We want to verify DDR stress test on IMX6 Quad, and we found our device can pass 400~600Mhz DDR stress test.

But it can't pass under 400 MHz test. We refer DDR bus frequency toggling 24MHz - 400MHz and checked the Dynamic Bus Frequency Driver (busfreq-imx.h, busfreq-imx.c):

/*
  * This enumerates the system bus and ddr frequencies in various modes.
  * BUS_FREQ_HIGH - DDR @ 528MHz, AHB @ 132MHz.
  * BUS_FREQ_MED - DDR @ 400MHz, AHB @ 132MHz
  * BUS_FREQ_AUDIO - DDR @ 50MHz/100MHz, AHB @ 24MHz.
  * BUS_FREQ_LOW  - DDR @ 24MHz, AHB @ 24MHz.
  * BUS_FREQ_ULTRA_LOW - DDR @ 1MHz, AHB - 3MHz.
  *
  * Drivers need to request/release the bus/ddr frequencies based on their performance
  * requirements. Drivers cannot request/release BUS_FREQ_ULTRA_LOW mode as
  * this mode is automatically entered from either BUS_FREQ_AUDIO or BUS_FREQ_LOW
  * modes.
  */
enum bus_freq_mode {
    BUS_FREQ_HIGH,
    BUS_FREQ_MED,
    BUS_FREQ_AUDIO,
    BUS_FREQ_LOW,
    BUS_FREQ_ULTRA_LOW,
};

Our questions:

1. The DDR frequency is toggling 24MHz - 528MHz on IMX6 Quad, is correct??

2. We need to test 24MHz - 528MHz DDR frequency range in DDR stress test, The ddr_stress_tester_v2.60 tool provides 135MHz - 672MHz test range. What criteria is frequency range does NXP suggest?

3. Our device can't pass under 400 MHz test, refer 3.3.2 Identifying Issue on Stress Test in Freescale i.MX6 DRAM Port

Application Guide-DDR3.pdf:

If the DDR3 cannot even pass the stress test at a low frequency, say 200 MHz, it is more likely to be a hardware problem. Then, it would be a good starting point to check the DDR3 connections. In addition,
you should check the power supply for the DDR3, i.MX6 MMDC and DDR3 I/O to see if voltage is valid and ripple is not too large.

It looks like the device must pass 200 MHz, and should we check our device hardware in this case?

Please provide some suggestions to us.

Thank you,

Arthur

[igorpadykov]

Hi Arthur

1. correct, for details please refer to Chapter 24 Dynamic Bus Frequency Driver attached Linux Manual.
2.3. for identifying issues please refer to i.MX6 System Development User’s Guide and recheck ddr settings

with DDR srcipt aid tool
https://community.nxp.com/docs/DOC-94917
http://cache.freescale.com/files/32bit/doc/user_guide/IMX6DQ6SDLHDG.pdf

Best regards
igor
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