i.MX6 u-boot: how to change DRAM cfg to adapt different DRAM frequencies in runtime

[mmj]

Dear All,

In u-boot, I have a i.MX6DL DRAM script for DDR frequency at 400MHz. For the DRAM to run at 100MHz, several MMDC parameters from the 400MHz script have to be updated. Thus it is not possible to use a single DRAM script for both DDR=400MHz and DDR=100MHz.

Is it possible for u-boot.imx to determine the current DRAM frequency and update the DRAM script in runtime? The scenario is if the fuse LPB_BOOT=11b is blown, the DRAM frequency will be become 132MHz and the u-boot.imx for DDR=400MHz will not boot. If I update the u-boot.imx for DDR=100MHz, the devices without blowing the LPB_BOOT=11b fuse will have DDR frequency running at 400MHz and the new u-boot.imx will not boot. So, I am looking for a method to update the MMDC parameters in u-boot.imx for different DRAM frequencies when boot up.

Thank you for your attention.

Regards,

mmj

[igorpadykov · Accepted solution]

Hi mmj

one can use plugin method (file plugin.S in uboot) to initialize the MMDC,

in plugin one can write simple asm routine and read fuses. In runtime

one will have to jump to iRAM, then reinitialize MMDC, this is not supported in

uboot so one will have to add codes for such procedure.

Best regards

igor

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