[Bug 240339] [ig4] I2C2 (touchpad bus) broken on the Google Pixelbook (Sunrise Point PCH)

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=240339

Vladimir Kondratyev <wulf at freebsd.org> changed:

           What    |Removed                     |Added
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                 CC|                            |wulf at freebsd.org

--- Comment #1 from Vladimir Kondratyev <wulf at freebsd.org> ---
(In reply to Greg V from comment #0)
Skylake's initialization currently broken due to SDA_HOLD register set too low.
Try following patch (power off is needed after install):

--- a/sys/dev/ichiic/ig4_iic.c
+++ b/sys/dev/ichiic/ig4_iic.c
@@ -590,6 +590,7 @@ ig4iic_attach(ig4iic_softc_t *sc)
        reg_write(sc, IG4_REG_SS_SCL_LCNT, 125);
        reg_write(sc, IG4_REG_FS_SCL_HCNT, 100);
        reg_write(sc, IG4_REG_FS_SCL_LCNT, 125);
+       reg_write(sc, IG4_REG_SDA_HOLD, 28);

        /*
         * Use a threshold of 1 so we get interrupted on each character,

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