topic i.MX6 DDR ZQ calibration when temperature changed in i.MX Processors

i.MX6 DDR ZQ calibration when temperature changed

torus1000 — Tue, 02 Jul 2019 10:26:41 GMT

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

Re: i.MX6 DDR ZQ calibration when temperature changed

igorpadykov — Tue, 02 Jul 2019 23:33:32 GMT

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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