Better DDR calibration and unknown issue for custom i.MX6Q board

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Better DDR calibration and unknown issue for custom i.MX6Q board

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torus1000
Contributor V

Hi,

We already activated ddr auto-calibration feature in uboot and it worked.

It was great but few issue remained. So we want to make sure the effectiveness of dynamic ddr calibration.

We assume DDR calibration usually done at 996MHz then bus clock fixed to 528MHz.

Actual core dynamically changes clock frequency likes 396,792 or 996MHz.

We are not sure about bus clock also dynamically change or not.

(Q) If DDR clock also dynamically changes, calibration value should also replaced, right?

       (Why same calibration value is enough for different bus clocks?)

According to our long term test, memory issue rarely recorded at the moment of core

clock change and issue cleared if clock frequency fixed (DVFS off).

(Q) Does anybody know such dynamic frequency related issues?

Can anybody help me?

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Yuri
NXP TechSupport
NXP TechSupport

Hello,

  it may be recommended to check memory, using calibration results

for highest DRAM frequency, for all range of frequencies with DDR stress

test (with incrementing frequencies) during long time. 


As for busfreq feature :

To enable the bus frequency driver, use the following command:

$ echo 1 > /sys/bus/platform/drivers/imx_busfreq/soc\:busfreq/enable

To disable the bus frequency driver, use the following command:

$ echo 0 > /sys/bus/platform/drivers/imx_busfreq/soc\:busfreq/enable

You may try both cases.

Note, problems with instability may be solved with additional caps.
Please look at the recommendations, linked below.

< https://community.nxp.com/servlet/JiveServlet/download/460403-1-284405/i.MX6%20Capacitor%20Placement...

Have a great day,
Yuri

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