Downgrade kernel

Hi, its seems to be a problem to between kernel 3.14 and Kwin with intel graphics (hd3000 in my cas), so in order to be able to use desktop effects, i need to downgrade the kernel, i read online about using:

emerge -p gentoo-sources-3.XX.XX-X… but i got

galadriel pitau # emerge -p =gentoo-sources-3.12.21-r1

Local copy of remote index is up-to-date and will be used.

* IMPORTANT: 4 config files in ‘/etc/portage’ need updating.
* See the CONFIGURATION FILES section of the emerge
* man page to learn how to update config files.

These are the packages that would be merged, in order:

Calculating dependencies… done!
[ebuild N ] sys-kernel/gentoo-sources-3.12.21-r1 USE="-build -deblob -experimental -symlink"

* IMPORTANT: 8 news items need reading for repository ‘gentoo’.
* Use eselect news to read news items.

and nothing else is done,also do i need to do something else, or just with that, emerge will update grub config too…

You can try this:

emerge -a =sys-kernel/calculate-sources-3.12.26 --autounmask-write
emerge -a =sys-kernel/calculate-sources-3.12.26