Wandboard: u-boot.img is getting too large

Hello,

Recently I started to notice that u-boot.img built for Wandboard by some toolchains becomes so large that it basically overlaps with U-Boot environment area on SD-card.

According to?http://wiki.wandboard.org/index.php/Boot-process#sdcard_boot_data_layout Wandboard's SD-card layout is as follows:
------------------------------>8---------------------------
# ?Offset (hex) (dec) ? Description
==========================================================
1. 0x00000000 Reserved For MBR
2. 0x00000200 512 Secondary Image Table (optional)
3. 0x00000400 1024 uBoot Image (Starting From IVT)
4. 0x00060000 393216 start of uboot env (size:8k)
5. 0x00062000 end of uboot env
6. 0x00100000 1048576 Linux kernel start
7. 0x0076AC00 7777280 start of partition 1
------------------------------>8---------------------------

So for U-Boot we have 383kB (392192 bytes).

But in up to date U-Boot for Wandboard we build separately ?a) SPL
?b) u-boot.img

which gives us a bit more detailed SD-card layout:
------------------------------>8--------------------------- # ?Offset (hex) (dec) ? Description
==========================
================================
1. 0x00000000 Reserved For MBR
2. 0x00000200 512 Secondary
Image Table (optional)
3. 0x00000400 1024 SPL
4. 0x00011400 ? 70656 u-boot.img
5. 0x00060000 39
3216 start of uboot env (size:8k)
6. 0x00062000 end of uboot env
...
------------------------------

From that layout we may calculate amount of space reserved for u-boot.img. It's just 315kb (322560 bytes).

Now if I build U-Boot with?Sourcery CodeBench ARM 2014.05 produced u-boot.img is already more than we expected (323840 bytes instead of "< 322560"):
------------------------------>8---------------------------
ls -la u-boot.img?
-rw-rw-r-- 1 user user 323840 Jul??5 07:38 u-boot.img ------------------------------>8---------------------------

Funny enough if I rebuild U-Boot with ARM toolchain available in my Fedora 23 distro u-boot.img becomes a little bit smaller:
------------------------------>8--------------------------- ls -la u-boot.img?
-rw-rw-r-- 1 user user 322216 Jul??5 07:39 u-boot.img ------------------------------>8---------------------------

What's worse this problem might not affect people most of the time because what happens people would just copy u-boot.img on SD-card and live in happiness with it... well until somebody attempts to save environment in U-Boot with "saveenv" command which will simply overwrite the very end of u-boot.img. That will lead to unusable SD-card until user dd u-boot.img on SD-card again.

I may foresee this issue in the future to become more visible once we add more features in U-Boot for Wandboard or just existing code base becomes bulkier and people will consistently get larger u-boot.img files produced.

IMHO there's an obvious solution for all that - just move U-Boot's env for say another 300-400k above like that:
------------------------------>8---------------------------

index 99f5c0c..e39583c 100644
@@ -181,7 +181,7 @@

?#define CONFIG_ENV_SIZE????????????????????????(8 * 1024) ?
?#define CONFIG_ENV_IS_IN_MMC
-#define CONFIG_ENV_OFFSET??????????????(6 * 64 * 1024) +#define CONFIG_ENV_OFFSET??????????????(2 * 6 * 64 * 1024) ?#define CONFIG_SYS_MMC_ENV_DEV?????????0
?
?#endif ------------------------------>8---------------------------

That might introduce incompatibility issues for those who used to modify default environment but given nobody noticed the problem in question it looks like there're not many of them.

Any thoughts are more than welcome.

-Alexey

Dear Alexey,

So they reserve 383 KiB for U-Boot, 8 kB for the environment, and then leave an unused gap of 632 KiB? That's silly.

Why place the environment anywhere in the middle of that free space? Just move it to the very end of it, i. e. make it

Offset Size Usage
1. 0x00000000 512 B Reserved For MBR
2. 0x00000200 512 B Secondary Image Table (optional)
3. 0x00000400 1015 KiB U-Boot image(s)
4. 0x000FE000 8 KiB U-Boot environment
6. 0x00100000 ... Linux kernel

Then you have all options open to grow even further, if needed, or allocate other stuff below the env without leaving a gap.

Gaps in a memory map are always begging for trouble, expecially when there is no reason for them.

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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like.                                               - Abraham Lincoln

Hi Wolfgang,

On Tue, 2016-07-05 at 08:11 +0200, Wolfgang Denk wrote:
Dear Alexey,

In message <1467694422.3144.32.camel at synopsys.com<mailto:[email protected]>> you wrote:

According to http://wiki.wandboard.org/index.php/Boot-process#sdcard_boot_data_layout
Wandboard's SD-card layout is as follows:
------------------------------>8---------------------------
# Offset (hex) (dec) Description
==========================================================
1. 0x00000000 Reserved For MBR
2. 0x00000200 512 Secondary Image Table (optional)
3. 0x00000400 1024 uBoot Image (Starting From IVT)
4. 0x00060000 393216 start of uboot env (size:8k)
5. 0x00062000 end of uboot env
6. 0x00100000 1048576 Linux kernel start
7. 0x0076AC00 7777280 start of partition 1
So they reserve 383 KiB for U-Boot, 8 kB for the environment, and then leave an unused gap of 632 KiB? That's silly.

IMHO there's an obvious solution for all that - just move U-Boot's env for say another 300-400k above like that:
Why place the environment anywhere in the middle of that free space? Just move it to the very end of it, i. e. make it

Offset Size Usage

1. 0x00000000  512 B   Reserved For MBR
2. 0x00000200  512 B   Secondary Image Table (optional)

3. 0x00000400 1015 KiB U-Boot image(s)
4. 0x000FE000 8 KiB U-Boot environment
6. 0x00100000 ... Linux kernel

Then you have all options open to grow even further, if needed, or allocate other stuff below the env without leaving a gap.

Gaps in a memory map are always begging for trouble, expecially when there is no reason for them.

Agree! IMHO solution to all that is simple.

I just want to get some feedback from people who maintain IMX/Wandboard boards or at least has better visibility at how people use these boards and if there's any rationale behind existing mapping.

If everybody is happy with proposal to move U-Boot env "partition" above I'll send a formal patch. Or I may as well send it and if there's interest in it somebody will pick it up and apply.

-Alexey

Hi Alexey,

I think this shows that we need to think about fixing this in one of the more common mx6/7 header files as a "board can override" default. And maybe start thinking about moving the questions to Kconfig as well, since tbot can make sure that the conversion is correct. :)

Tom
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