i.MX ProcessorsのトピックRe: Does u-boot run in RAM or in the boot device ?

Does u-boot run in RAM or in the boot device ?

rans — Fri, 19 Jan 2018 15:33:51 GMT

Hello,

I try to get better understanding of u-boot initialization.

From my reading, it seems that there are 2 methods of boot:

1. boot the u-boot.imx from the device boot

2. boot spl which initialize ddr, and then load u-boot from the boot device (into DDR?) ?

As to (1) option above, is it that u-boot runs in the boot device or in RAM ?

Another question:

what's the purpose of pmic and rtc initalization (with i2c) ?

Why can't kernel do that ?

Thank you,

Ran

Re: Does u-boot run in RAM or in the boot device ?

igorpadykov — Fri, 19 Jan 2018 23:25:24 GMT

Hi Ran

you are right, there are two uboot versions: directly run uboot and two steps process,
first "spl" small loader then it initializes chip peripherals and run remaining uboot.

Purpose of uboot pmic and rtc initalization (with i2c) is to prepare necessary pmic
voltages for running linux. It is convenient to do this in uboot, not kernel, so any kernel image
could be portable and be able to run on different uboot versions/boards,

Best regards
igor
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Re: Does u-boot run in RAM or in the boot device ?

rans — Tue, 06 Mar 2018 20:54:09 GMT

Hello Igor,

So, in imx6 there is no "early u-boot", but only one u-boot , Right ?

Does it run from RAM ? If so, who initialized RAM before u-boot was loaded to RAM ?

Thanks,

ranran

Re: Does u-boot run in RAM or in the boot device ?

igorpadykov — Tue, 06 Mar 2018 23:57:06 GMT

Hi Ran

early initialization is done in ROM using Device Configuration Data (DCD),

described in Boot Chapter of Reference Manual.

Best regards
igor