Hi Heikki,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   707b4f493e77638387f29d5ea35e383c418e710d
commit: d9eda9bab237259b06690652b145d19e0ce37a77 serial: 8250_pci: Intel MID UART support to its own driver
date:   5 weeks ago
config: x86_64-randconfig-x011-11220649 (attached as .config)
reproduce:
        git checkout d9eda9bab237259b06690652b145d19e0ce37a77
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

>> ERROR: "rational_best_approximation" [drivers/tty/serial/8250/8250_mid.ko] undefined!

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