i.MX6 DDR ZQ calibration when temperature changed

[torus1000]

Hi

According to p7 of AN4467: https://www.nxp.com/docs/en/application-note/AN4467.pdf
ZQ calibration auto initialization mode is strongly recommended for keeping the ZQ registers calibrated during i.MX 6 Series operating modes and ambient temperature changes.

I guess some drivers in kernel done "force initiated hardware ZQ calibration" when temperature changed.

BTW I believe "auto initiated hardware ZQ calibration" done periodically.

Is my guess correct? (Is such recommendation supported by OS?)

Could someone let me know the url of the source code regarding above feature?
    e.g https://source.codeaurora.org/external/imx/linux-imx/tree/drivers?h=imx_4.14.98_2.0.0_ga

[igorpadykov · Accepted solution]

Hi torus

yes software performs calibartion in linux/arch/arm/mach-imx/ddr3_freq_imx6.S

in cpufreq driver described in attached Linux Manual when changing frequency

(also due to temperature)

ddr3_freq_imx6.S\mach-imx\arm\arch - linux-imx - i.MX Linux kernel 

Best regards
igor
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