[OpenWrt-Devel] u-boot/lantiq: gcc7 incompatibility: resets when trying to access network

[Martin Schiller]

On 2018-09-24 13:14, Martin Schiller wrote:
> Hi,
> 
> I've got some problems with the lantiq uboot in combination with the
> (default) gcc 7.x compiler.
> 
> Setting "OPTFLAGS" in uboot's config.mk to "-O2" or the default "-Os"
> leads to the following behaviour:
> 
> The uboot compiles well, but when you try o access the ethernet
> network (ping/tftboot) the device do a RESET:
> 
> (tested on a Lantiq VRX268 v1.2)
> 
> ----------------------------------------------------
> ....
> VR2020 # ping 192.168.1.20
> ltq_phy: addr 1, link 0, speed 10, duplex 0
> ltq_phy: addr 17, link 0, speed 10, duplex 0
> ltq_phy: addr 18, link 0, speed 10, duplex 0
> ltq_phy: addr 19, link 1, speed 100, duplex 1
> ltq_phy: addr 20, link 0, speed 10, duplex 0
> Using ltq-eth device
> 
> ROM VER: 1.1.4
> CFG 04
> _�
> ROM VER: 1.1.4
> CFG 04
> EEPROM Data OK
> UART
> 
> ----------------------------------------------------
> 
> doing the same with "OPTFLAGS" set to "-O1" everything works fine:
> 
> ----------------------------------------------------
> ...
> VR2020 # ping 192.168.1.20
> ltq_phy: addr 1, link 0, speed 10, duplex 0
> ltq_phy: addr 17, link 0, speed 10, duplex 0
> ltq_phy: addr 18, link 0, speed 10, duplex 0
> ltq_phy: addr 19, link 1, speed 100, duplex 1
> ltq_phy: addr 20, link 0, speed 10, duplex 0
> Using ltq-eth device
> host 192.168.1.20 is alive
> VR2020 #
> ----------------------------------------------------
> 
> When using gcc 6.x or 5.x, "OPTFLAGS=-Os" also works.
> 
> Any ideas how to get "OPTFLAGS=-Os" working again with gcc 7.x?

Ok, found out that '-fstore-merging' is responsible for the crash, which 
is enabled with "-02" in gcc 7.x by default.

Adding "-fno-store-merging" to "OPTFLAGS" fixes the problem.

Here is also a "statement" to this problem:

https://patchwork.ozlabs.org/patch/792238/

How should we proceed now for our uboot-lantiq?

- Martin

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