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.
Besides that I still think the correct solution would be to use the arm-headers as found in the current linux kernel. The problem is, that I don't know (haven't looked up) the reasons for changes in the arm-linux-headers as currently found in u-boot.
And because updating those headers might require some more changes in various other places in u-boot, I think it would be good if one of the u-boot-arm-maintainers would do that. I'm not that much involved in u-boot-development, don't follow the ml closely and therefor might miss necessary changes when taking the current arm-headers from the kernel and dropping them into u-boot.
Regards,
Alexander