[Bug 221777] merge the latest changes to the ig4 module from DragonFly BSD and add Kaby Lake / Intel 100 series platform support

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221777

--- Comment #7 from marc.priggemeyer at gmail.com ---
(In reply to Oleksandr Tymoshenko from comment #6)

Please consider these two parts from the patch I provided last year:

In ig4_reg.h:
+/* Newer versions of the I2C controller allow to check whether
+ * the above ASSERT/DEASSERT is necessary by querying the DEVIDLE_CONTROL
+ * register.
+ * 
+ * the RESTORE_REQUIRED bit can be cleared by writing 1
+ * the DEVICE_IDLE status can be set to put the controller in an idle state
+ * */
+
+#define IG4_RESTORE_REQUIRED   0x0008
+#define IG4_DEVICE_IDLE                0x0004

and in ig4_iic.c
+       v = reg_read(sc, IG4_REG_DEVIDLE_CTRL);
+       if (sc->version == IG4_SKYLAKE && (v & IG4_RESTORE_REQUIRED) ) {
+               reg_write(sc, IG4_REG_DEVIDLE_CTRL, IG4_DEVICE_IDLE |
IG4_RESTORE_REQUIRED);
+               reg_write(sc, IG4_REG_DEVIDLE_CTRL, 0);
+
+               reg_write(sc, IG4_REG_RESETS_SKL, IG4_RESETS_ASSERT_SKL);
+               reg_write(sc, IG4_REG_RESETS_SKL, IG4_RESETS_DEASSERT_SKL);
+               DELAY(1000);
+       }


This reinitialization makes sure to activate the I2C controller after power
down if necessary. It is based on the Intel 100 series PCH documentation.

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