[U-Boot] [PATCH] ARM: mx6: Enable MMC FS boot support

[Marek Vasut <marex@denx.de>]

On 04/28/2016 01:32 AM, Robert Nelson wrote:
> 
> 
> On Wed, Apr 27, 2016 at 6:28 PM, Marek Vasut <marex@denx.de
> <mailto:marex@denx.de>> wrote:
> 
>     On 04/28/2016 01:16 AM, Tom Rini wrote:
>     > On Thu, Apr 28, 2016 at 01:06:07AM +0200, Marek Vasut wrote:
>     >
>     >> Enable support for booting U-Boot image from filesystem instead of some
>     >> random offset on the SD card. This makes the board usable by putting the
>     >> u-boot.img to first partition of the SD card and writing the SPL this way:
>     >> $ dd if=u-boot-with-spl.imx of=/dev/sdX seek=2 bs=512
>     >
>     > Wait, you're still writing u-boot + SPL to the device and not just SPL,
>     > but it's still preferring the filesystem one over the appended one?
>     >
> 
>     Ha, good point. I should've written the 'SPL' file instead, which is
>     just the SPL without U-Boot. I don't want to install U-Boot to random
>     offset on the SD card as it has the potential to corrupt data if the
>     u-boot binary changes in size.
> 
>     If I install u-boot image to random offset 138 blocks from the start of
>     SD card, it will boot that, otherwise it will load from FS.
> 
>     I will update the commit message with the correct info, sorry.
> 
> 
> Oh, we went thru this last year...
> 
> http://lists.denx.de/pipermail/u-boot/2015-August/222061.html
> 
> If your serious about changing "one" i.mx6 board, you need to change
> them "all".

No, I do not have to change and will not change any other boards I
cannot test.

> Otherwise leave a 1MB hole on your mmc partition and dd spl/u-boot.img
> as that works for ti/imx/sunxi...

No, this design is utterly broken. If U-Boot grows beyond 1 MiB, it will
corrupt my data, silently. I will not have this. I would much rather see
these broken designs go away and have everyone move to
SPL in random location as mandated by BootROM (unfortunately) and
u-boot.img on a filesystem. That way, u-boot.img can grow and shrink
either way, without endangering any surrounding data.

Can you give me any argument why writing u-boot.img to random location
on the SD card is better than storing it on a filesystem ?

> Regards,
> 
> -- 
> Robert Nelson
> https://rcn-ee.com/


-- 
Best regards,
Marek Vasut