topic Re: Setting "Reserved For MBR" option in i.MX Processors

Setting "Reserved For MBR" option

ko-hey — Wed, 09 Aug 2017 00:38:20 GMT

Hi all

There is a MBR option for boot of i.MX7 in reference manual of Figure 6-38.

But there is little explanation for MBR option.

http://www.nxp.com/docs/en/reference-manual/IMX7DRM.pdf

Q1.

Is there any hardware setting bit for MBR option ?

Q2.

If Q1 is yes, which bit does user set ?

Q3.

If Q1 is no, I think user set by their software, do you have any example for set it ?

Q4.

When user doesn't use the option, do we need to set 0x00 to MBR region ?

Q5.

In case of user doesn't use the option, if undefined values are written in the MBR area, will there be any difference in behavior after booting ?

Please contact me if it's lack of info.

Ko-hey

Re: Setting "Reserved For MBR" option

b36401 — Thu, 10 Aug 2017 09:24:21 GMT

This place is reserved for usage as MBR of storage device. We do not use it however in case of some software uses MBR etc it's place is reserved.
So the structure should be filled as that software needs.
Or you can left the data untouched if you do not plan to use it.

Have a great day,
Victor

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Re: Setting "Reserved For MBR" option

ko-hey — Fri, 25 Aug 2017 00:41:25 GMT

Hi b36401‌

Sorry for late reply.

First of all, let me confirm the meaning of "MBR". MBR means "Master Boot Record". Am I correct ?

I can't understand the use case of MBR.

Could you give me the example case ? Is it depend on storage device ?

Here is a Expansion Device Structures Layout from reference manual.

Can user set start address 0x00000000 when user don't use MBR and Secondary Image Table ?

Ko-hey

Re: Setting "Reserved For MBR" option

b36401 — Fri, 25 Aug 2017 04:09:33 GMT

In an age of MSDOS first 512-bytes sector of physical drive was used for two purposes:
1. it contained a boot loader.
2. it contained the partition table.
So it was named "boot record".

Now it is used only as partition table. Only its tail is used for 4 16-bytes records to describe 4 partitions.

And more over. If you do not plan to use partitions on this expansion device you can ignore MBR at all.

Have a great day,
Victor

Re: Setting "Reserved For MBR" option

ko-hey — Mon, 28 Aug 2017 08:06:18 GMT

Hi Victor Linnik

And more over. If you do not plan to use partitions on this expansion device you can ignore MBR at all.

Let me confirm about the meaning of above comment.

Do you mean can user set start address 0x00000000 when user don't use MBR and Secondary Image Table ?

Ko-hey

Re: Setting "Reserved For MBR" option

b36401 — Wed, 30 Aug 2017 05:28:32 GMT

I mean you can disregard this table if you do not plan to use storage device natively in the OS.
However for some better compatibility it is recommended to have valid partition table on the device.

Re: Setting "Reserved For MBR" option

ko-hey — Wed, 30 Aug 2017 07:19:49 GMT

Hi Victor Linnik

I understand user can ignore the table when they don't use storage and you recommended to have build partition.

Ko-hey