i.MX Processors中的主题 Re: How does u-boot read dcd table?

How does u-boot read dcd table?

eddiehuang — Wed, 24 Jun 2015 09:08:28 GMT

Hi there,

In U-boot of imx.51 I understand the start position of SD card booting is 0x400, and there's a command for cpu to jump to _start. However, all DCD entries reside between 0x400 and _start. So how does cpu come back and read these DCD entries to complete DDR controller configuration? Thanks.

Re: How does u-boot read dcd table?

Yuri — Thu, 25 Jun 2015 02:25:56 GMT

The boot ROM of the i.MX51 copies the whole block (2K / 4K) to internal memory

in order to analyze it. Please refer to Figure 1 (Secure Boot Flow from Device)

of the app note AN4547 (Secure Boot on i.MX25, i.MX35, and i.MX51

using HABv3)

http://cache.freescale.com/files/32bit/doc/app_note/AN4547.pdf

Have a great day,
Yuri

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Re: How does u-boot read dcd table?

igorpadykov — Thu, 25 Jun 2015 02:50:46 GMT

Hi eddie

iROM automatically seeks DCD data, based on boot settings,

boot flow similar to sect.7.6.2 Device Configuration Data (DCD) IMX53RM

Best regards

igor

Re: How does u-boot read dcd table?

eddiehuang — Thu, 25 Jun 2015 05:26:12 GMT

Appreciate that. I did this study for a while and I was assuming the memory controller will be set in lowlevel_init.S. Does it mean memory controller configurations are done before _reset? It looks dcd are done in the very first beginning!