On 13/02/2018 at 18:56:34 -0500, Peter Milley wrote:

Okay, I've booted the new kernel.

peter@haven:~$ uname -a
Linux haven 4.16.0-rc1+ #32 SMP Tue Feb 13 22:11:39 CET 2018 x86_64
x86_64 x86_64 GNU/Linux
peter@haven:~$ dmesg | grep -i rtc
[    0.045403] RTC time: 23:46:52, date: 02/13/18
[    1.368198] rtc_cmos 00:01: RTC can wake from S4
[    1.368205] rtc_cmos: drivers/rtc/rtc-cmos.c +679 cmos_do_probe
[    1.368235] rtc_cmos: drivers/rtc/rtc-cmos.c +684 cmos_do_probe
[    1.368260] rtc_cmos: drivers/rtc/rtc-cmos.c +688 cmos_do_probe
[    1.368285] rtc_cmos: 1: 70 8
[    1.368302] rtc_cmos: probe of 00:01 failed with error -16
[    1.408861] hctosys: unable to open rtc device (rtc0)

[...]

And /proc/ioports:
peter@haven:~$ sudo cat /proc/ioports
0000-0cf7 : PCI Bus 0000:00
  0000-001f : dma1
  0020-0021 : pic1
  0040-0043 : timer0
  0050-0053 : timer1
  0060-0060 : keyboard
  0062-0062 : PNP0C09:00
    0062-0062 : EC data
  0064-0064 : keyboard
  0066-0066 : PNP0C09:00
    0066-0066 : EC cmd
  0070-0072 : wdat_wdt

So I can tell you what is happening but I can't tell you why. You have a
watchdog at 0x70 (size 2) and the RTC at 0x70 (size 8).

Because the watchdog driver is probed first and it requests the io
region, when the RTC driver is probed, it fails to request the same
region.

Maybe your 4.10 kernel didn't have CONFIG_WDAT_WDT (this appeared in
4.9).
I'm afraid, that is as far as I can help, you'd have to ask someone that
is more knowledgeable about x86 to go further (I've added the wdat_wdt
driver author in Cc).

-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com