The commit 
53d7d69d8ffdfa60c5b66cc2e9ee0774aaaef5c0
    ALSA: hdmi - support infoframe for DisplayPort
dropped the initialization of CA field accidentally.
This resulted in only two-channel LPCM mode on Nvidia machines.
Reference: kernel bug 28592
	https://bugzilla.kernel.org/show_bug.cgi?id=28592
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Cc: <stable@kernel.org>
 
                        hdmi_ai->ver            = 0x01;
                        hdmi_ai->len            = 0x0a;
                        hdmi_ai->CC02_CT47      = channels - 1;
+                       hdmi_ai->CA             = ca;
                        hdmi_checksum_audio_infoframe(hdmi_ai);
                } else if (spec->sink_eld[i].conn_type == 1) { /* DisplayPort */
                        struct dp_audio_infoframe *dp_ai;
                        dp_ai->len              = 0x1b;
                        dp_ai->ver              = 0x11 << 2;
                        dp_ai->CC02_CT47        = channels - 1;
+                       dp_ai->CA               = ca;
                } else {
                        snd_printd("HDMI: unknown connection type at pin %d\n",
                                   pin_nid);