[U-Boot] [PATCH v3] ARM: Avoid compiler optimization for usages of readb, writeb and friends.

Dirk Behme
2011-01-01T19:21:42Z

On 01.01.2011 19:47, Alexander Holler wrote:
> Am 01.01.2011 19:25, schrieb Dirk Behme:
>> On 01.01.2011 18:52, Alexander Holler wrote:
>>> Hello,
>>>
>>> Am 01.01.2011 13:04, schrieb Dirk Behme:
>>>> On 22.12.2010 12:04, Alexander Holler wrote:
>>>>> gcc 4.5.1 seems to ignore (at least some) volatile definitions,
>>>>> avoid that as done in the kernel.
>>>>>
>>>>> Reading C99 6.7.3 8 and the comment 114) there, I think it is a
>>>>> bug of
>>>>> that
>>>>> gcc version to ignore the volatile type qualifier used e.g. in
>>>>> __arch_getl().
>>>>> Anyway, using a definition as in the kernel headers avoids such
>>>>> optimizations when
>>>>> gcc 4.5.1 is used.
>>>>>
>>>>> Maybe the headers as used in the current linux-kernel should be
>>>>> used,
>>>>> but to avoid large changes, I've just added a small change to the
>>>>> current headers.
>>>
>>>> Do you like to test the patch in the attachment? I named it 'v4'.
>>>>
>>>> After some thinking and testing, it seems to me that the volatile
>>>> optimization issue this patch shall fix is only with the readx()
>>>> macros.
>>>> So the idea is to drop all writex() changes done in the v3 version of
>>>> this patch. With dropping the writex() changes, we would drop all
>>>> issues
>>>> we discussed with e.g. the GCC statement-expression and the do while
>>>> workaround, too.
>>>
>>> I've come across a bug which reads as the problem might be fixed in
>>> gcc 4.5.2:
>>>
>>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45052
>>>
>>> I will test gcc 4.5.2 in the next days.
>>
>> Have you been able to test v4 of the patch I sent with gcc 4.5.1?
>
> No, sorry, I don't have a test case for consequent write* and I will
> have to write one.

?

If I remember correctly, the test case for this patch was compiling
U-Boot with 4.5.1 and then check

a) if it boots at Beagle (correct clock.c)
b) if NAND works ok (correct omap_gpmc.c)

?

Thanks

Dirk