[U-Boot] [PATCH] arch: armv8: Remove the error when dcache is off

[Michal Simek]

On 27.6.2017 13:46, Alexander Graf wrote:
> 
> 
> On 27.06.17 13:20, Michal Simek wrote:
>> Hi,
>>
>> On 27.6.2017 13:01, Alexander Graf wrote:
>>> I don't think that's going to work - at least not without compiler flag
>>> changes. By default, gcc will happily generate unaligned accesses. If
>>> you disable dcache, these will trap.
>>
>> What's that compiler flags we should be using to avoid that?
> 
> It's a combination of
> 
>   -mstrict-align
> 
> plus crossing fingers with lots of praying plus making sure that every
> code you call also follows -mstrict-align plus double-checking that you
> don't break the kernel booting ABI:
> 
> 
> http://elixir.free-electrons.com/linux/v4.12-rc7/source/Documentation/arm64/booting.txt
> 
> 
> In the booti case, disabling dcache seems to be legitimate. In the
> bootefi case however, it's not.

Non wants to boot the kernel. It is really about programming stuff.

> 
> So you will also need to set CONFIG_EFI_LOADER to depend on
> !CONFIG_SYS_DCACHE_OFF which means you will want to convert
> CONFIG_SYS_DCACHE_OFF to Kconfig first :).

ok. I will let Siva to do it just wanted to refresh this topic.


>> The reason for this change is to have really small u-boot which fits to
>> OCM without DDR to be able to do initial programming.
> 
> Yup, makes sense. I'm just slightly scared by the idea :).

The same stuff we did on Zynq in past.
I have never had enough time to look at that MMU mapping why it is so
huge. Maybe reduce size of that tables or using different page size is
better way to go.

Thanks,
Michal