[U-Boot] [PATCH 4/6] davinci_emac: fix for running with dcache enabled

[Anton Staaf]

On Mon, Oct 10, 2011 at 11:31 AM, Wolfgang Denk <wd at denx.de> wrote:
> Dear Anton Staaf,
>
> In message <CAF6FioWbLz9JKBnj5sJGALtj=bJyLNbFvunNa6FE62y42t6-hw at mail.gmail.com> you wrote:
>>
>> > When PPC was building again, I tested it on ARM (which I assumed was
>> > OK, given that this was Anton's primary architecture). =A0That was when
>> > I finally gave up, see
>>
>> Yes, the patches expose the fact that almost no boards define
>> CONFIG_SYS_CACHELINE_SIZE.
>
> Um...
>
> -> ls include/configs/* | wc -l
> 577
> -> grep CONFIG_SYS_CACHELINE_SIZE include/configs/* | wc -l
> 199
>
> So that's more than one third of all boards - most of them PPC...

Yes, sorry, I should have said almost no architectures define it, PPC being
the exception.

>> I am working on a "solution" for this.  My first thought is to add defines
>> for
>> CONFIG_SYS_CACHELINE_SIZE in all of the arch cache.h files that
>> currently do not have them.
>> This would be all cache.h files other than the PPC one.  But this
>> could be a huge amount of work
>> to look up all of the arch cacheline sizes.  So I am thinking of
>> putting in a wrong, but large power
>> of two so that boards will build and probably work.  But will
>> certainly need to be fixed up...
>
> Please don't - bogus stuff that appears to be working is known to
> never get fixed.  Let's rather break the boards - this enforces the
> needed clean-up.

Yes, that's my feeling as well.

>> Another solution would be to do the above and define
>> CONFIG_SYS_CACHELINE_SIZE as a
>> large (128?) value and then indicate that that config is to deprecated
>> in favor of Mikes suggestion
>> of using the Linux CACHE BITS defines.  Then we can move boards over
>> to that mechanism
>> over time, and in the mean time all boards will compile, and
>> architectures/boards that correctly
>> define their cacheline size will function correctly, and
>> architectures/boards that use the large default
>> will most likely function correctly...
>
> At least a big, dfat build warning must be issued, then (but only one,
> not a loooooong list).

Would you be OK with a build warning for the lack of definition of
CONFIG_SYS_CACHELINE_SIZE like I have now if it only happened
once per board?  I could move it from common.h to a c file that is always
built.  Perhaps I could add a checks.c file to libgeneric?  I'm not really sure
if that's the right place for it.  Do you have a suggestion?

This new file would include asm/cache.h and then common.h.  It would then
have a #ifdef to check for CONFIG_SYS_CACHELINE_SIZE.  So any arch
that defined it in it's asm/cache.h or any board that defined it in
it's config file
would be OK.  All other boards would generate a single compiler warning
when building that file.

What do you think?

I would have to add a couple of empty asm/cache.h files for the architectures
that don't currently have them.

Thanks,
     Anton

> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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